Journal of the Neurological Sciences, 1976, 28 : 147-157
147
© Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
P A R K I N S O N I A N AKINESIA, R I G I D I T Y A N D T R E M O R IN T H E M O N K E Y Histopathological and Neuropharmacological Study
J. C. PI~CHADRE*, L. LAROCHELLE** AND L. J. PO1RIER
Laboratoires de Neurobiologie, Facultd de M6decine, Universit~Laval, Quebec, P. Q. G I K 7P4 (Canada) (Received 28 August, 1975)
SUMMARY
Parkinsonian postural tremor and rigidity most likely involve the disruption of the dopaminergic (DA) nigrostriatal mechanisms and the corresponding rubroolivo-cerebello-rubral loop without excluding the involvement of related dentatorubral and dentato-thalamic nervous fascicles. The integrity of the magnocellular division of the red nucleus and of the rubrotegmentospinal pathway, however, is apparently essential for the expression of rigidity. Akinesia most likely results from the bilateral involvement of brain stem catecholaminergic (CA) mechanisms including the DA nigrostriatal pathways. Finally the integrity of the pallidothalamic fibers seems to represent an essential feature for the improvement of these motor disorders by DA agonists, suggesting that certain of these agents, such as apomorphine, exert their main effects through the neostriatal DA receptors.
INTRODUCTION
In a previous study (Poirier 1960) the most characteristic motor disturbances of Parkinsonism, akinesia, rigidity and tremor, had been reproduced by upper brain stem tegmental lesions in 2 monkeys. Other animals described in the same paper (Poirier 1960) and in another report (Poirier, Bouvier, B6dard, Boucher, Larochelle, Olivier and Singh 1969), however, displayed sustained postural tremor most often associated with hypotonicity and hypokinesia of one or several limbs following somewhat differently placed lesions. This work was supported by the Medical Research Council of Canada. * Supported by the Quebec Medical Research Council. ** Scholar of Medical Research Council of Canada,
148 A-SPONTANEOUS
TREMOR
Biceps
Triceps
sec
B- P A S S I V E .......
MOVEMENTS
FL EX~O N - - - ' ~ "
. . . .
EXTENSLON .........
-{--
~:L ~ × I O N . . . .
Triceps
C - - J sec
Fig. I. Electromyographic recordings in monkes, PI show,ing tremor and rigidity: ,4: spontaneou~ rhythmic bursts of EMG activity al a fiequency close Io 7/s and alternating in the biceps arid triceps muscles; B: rigidity is evidenced by the strong reflex activity in the stretched muscles. A cog-wheel phenomenon, also experienced clinically during passive movements is evidenced by the rhythnlic bursts, at the frequency of tremor, displayed by the stretched muscles.
Fig. 2.
149
Fig. 3.
Figs. 2-4. Transverse sections through upper brain stem of monkey P1 illustrating bilateral lesions involving the caudal hypothalamus, medial subthalamus and rostral midbrain (2-3). Fig. 4 represents a transverse section through caudal midbrain to show sparing of the magnocellular division of the red nucleus. Note also almost total cell loss in both substantia nigra. L, lesion; RN, red nucleus, magnocellular division; SN, substantia nigra. Basic fuchsin and fast blue, >: 7, x 7 and ×20, respectively.
150
In the present study we succeeded in reproducing akinesia, rigidity (assocmted with the cog-wheel phenomenon) and tremor in 2 other monkeys and akinesia or bradykinesia in several other monkeys following bilateral upper brain stem tegmental lesions. Moreover neuropharmacological data obtained in these animals together with the histopathological findings permit us to arrive to more specific conclusions concerning the mechanisms involved in these types of motor disorders. Certain results including electrophysiological data obtained in one animal of this series (Pl) were published in preliminary notes (Filion, Larochelle and Poirier 1974; Larochclte, Pdchadre and Poirier 1974) and a review article (Poirier, Filion, Langelier and Larochelle 1975). MATERIAL AND METHODS
In all 9 animals of this series the lesions were produced, under pentobarbital anesthesia, by electrocoagulation using a high-frequency current directed tilrough a monopolar electrode stereotaxically introduced in the brain. Postoperatively the animals were regularly observed and the effects of either apomorphine, tevodopa or piribedil (ET-495, Laboratoires Servier, Orl6ans), all of which are ciopamine agonists, on the motor disturbances were tested. Their behavior was cinematographically recorded and EMGs of the tremor-affected and hypertonic muscles were made, EMGs were taken with copper wires introduced into tile muscles through hypodermic needles. A Gould pen recorder (Model 440) was used for recording the EMG aclivity The animals were killed by an overdose of pentobarbital and their brains were fixed in a solution of 10 °~i neutral formalin. Serial sections of the brains were prepared and stained with basic fuchsin and fast blue. RESULTS
Akinesia, rigidity and tremor (monkeys Pl and P2~ Following incomplete lesions of the cerebellar dentate nuclei monkey PI did not show any detectable motor impairment. Nine months later bilateral tegmental lesions (the 2 lesions made 10 days apart) were produced Following these lesions the animal gradually (within 5 days) became aphagic, profoundly akinetic and displayed postural tremor and rigidity of the four limbs. Rigidity characterized by increased resistance to passive movements was associated with the cog-wheel phenomenon in the 4 limbs (Fig. I). He had tc be force-fed daily and the motor disturbances remained unchanged during the whole 9 weeks postoperative period. The administration of a single dose of levodopa (30 mg/kg, i.p.) produced no noticeable effect on the motor impairments whereas the injection of apomorphine ~0.0150.2 mg/kg, i.m.) or piribeOil ( 1.5-2.5 mg/kg, i.m.) repeatedly counteracted the abovedesclibed motor disturbances for a 30-90 min period. Under such conditions the animal ran and ate spontaneously and the tremor and rigidity of the limbs vanished. In this animal (P 1) the bilateral brain stem lesions involve the ventromedial tegmental area of the upper midbrain, tile caudal part of the hypothalamus and the medial
151 TABLE
1
STRUCTURES
Monkeys
EXTENSIVELY
Red
nucelus
M
P
INVOLVED
Cere
AND
Nigrostriatal
bello- fibers fugal fibers m i d brain
ASSOCIATED
Pallido-
Tremor
MOTOR
DISTURBANCES
Rigidity
AkinesiaBrady-
fugal
kinesia
fibers
hypothalamus
P1
--
B
B
B
B
--
B
B
Pr
P2
--
R
R
B
--
--
L
L
Pr
---
P3
--
R
B
B
Ab
Ab
Pr
--
P4
--
--
--
B
R
--
Ab
Ab
Pr
--
P5
--
--
--
B
--
--
Ab
Ab
Pr
--
P6
--
--
B
B
--
Ab
Ab
Pr
--
P7
--
L
--
B
B
Ab
Ab
--
Pr
P8
--
--
--
B
B
Ab
Ab
--
Pr
P9
--
--
--
B
B
Ab
Ab
--
Pr
Ab
=
absent;
of red nucleus;
B = Pr
bilateral; =
L, R =
left and
right;
M, P =
magnocellular
and
parvocellular
division
present.
part of the subthalamus (Figs. 2 and 3). The lesions which are very close to the interpeduncular fossa at upper midbrain level are associated with an almost complete degeneration of the neurons of the substantia nigra and nuclei paranigralis, linearis and parabrachialis pigmentosus on both sides. More dorsally, the lesions destroy most of the parvocellular division of the red nuclei and interrupt corresponding cerebellothalamic fibers. The magnocellular division of the red nuclei and corresponding rubral and tegmental descending pathways, however, are spared (Fig. 4). At diencephalic level the lesions destroy most of the structures in the caudal third of the hypothalamus and the more medially located structures of the subthalamus sparing, however, most of the subthalamic nucleus and the pallidothalamic fibers corresponding to Forel's H fields (Fig. 2). The neurons of both divisions of the pallidum are apparently normal (Table 1). Monkey P2 also became gradually akinetic but not aphagic following the production of bilateral tegmental lesions (the 2 lesions made 8 days apart). The akinesia was associated with postural tremor and rigidity (including the cog-wheel phenomenon) of the left limbs. These motor disturbances which were present during the whole postoperative period of 4 weeks were counteracted by apomorphine (0.2 mg/kg, i.m.). In this animal the lesions extending close to the interpeduncular fossa bilaterally involve the ventromedial tegmental area of the upper midbrain. They resulted in almost total cell losses of the substantia nigra and nuclei paranigralis, linearis and parabrachialis pigmentosus. In addition the parvocellular division of the red nucleus and ascending cerebellothalamic fibers are extensively destroyed on the right side and very slightly damaged on the left side. The magnocellular division of the red nucleus, the rubrotegmentospinal tract as well as the hypothalamus and subthalamus are spared on both sides (Fig. 5, Table 1).
152
l-ig. 5. l-ransverse scctioi? lhrough upper brain slem of T~loi~kcy P2 lo illustrate sparing ol cauda hvpothalamus and subthalamus. Same slain. 7
Fig. 6. Transverse section through upper midbram of monkey 1'6 to illustrate bilateral veJ~tromedia tegmental lesions. Same stain, 7.
153
Fig. 7. Transverse section through diencephalon of monkey P7 showing bilateral and extensive lesions involving the hypothalamus and medial subthalamus. Note extensive destruction of Ford's H fields. Same stain, × 7.
Akinesia and prostration (monkeys P3-P6) Four other monkeys survived 14 (P3 and P4), 6 (P5) and 7 days (P6), respectively, following bilateral tegmental lesions (the 2 lesions made a few days apart). All 4 animals which were relatively alert and active and ate spontaneously in the immediate postoperative days gradually became profoundly akinetic and aphagic and finally prostrated and died. They did not show any tremor or rigidity of the limbs. Apomorphine (0.2 mg/kg, i.m.) tested in only one of these 4 monkeys (P3) one week after the operation transiently rendered the animal more active. He spontaneously ate and drank. In all 4 animals the bilateral lesions involve the ventromedial part of the rostral midbrain and impinge on the medial part of the subthalamus (Fig. 6). The hypothalamus (at the level of the caudal part of the mamillary body) is invaded bilaterally in two monkeys (P3, P6), and unilaterally in another monkey (P4) (Table l). Bradykinesia (monkeys P7-P9) Three other monkeys (P7, P8, P9) became bradykinetic following bilateral brain stem lesions of the hypothalamus which spared the midbrain. When attacked, however, they ran away. Neither tremor nor rigidity was present Jn these two animals, Apomorphine (0.4 mg/kg, i.m.) did not improve bradykinesia in contrast to the effect of this drug on akinesia in monkeys P1, P2 and P3. On the contrary the 3 animals froze instead of showing signs of hyperexcitability usually observed in other monkeys.
154
THALAMUS VA VL
•
\."x2. HYPOTHALAMU~
,. GLOBUS i PALLIDUS
PARVO RED NUCLEUS MAGNC
%
CEREBELLUM
/
SUBSTANTIA NIGRA
i d ~ I N F . OLIVE Fig. 8. Schematic drawing Io illustrate the main nervous structures bilaterally involved in monkey PI that showed sustained akinesia, rigidity and tremor. They include the parvoceltular division of the red nucleus and corresponding rubro-olivary fibers, the nigrostriatal pathway and cerebello-thalamic and cerebello-rubral ascending fibers.
The lesions in these 3 animals, as illustrated on Fig. 7, bilateraity destroy most of the structures at the level of the caudal hypothalamus including the nigrostriatal pathways. Moreover at the level of Ford's H fields they completely and bilaterally interrupt the pallidofugal fibers (Table 1). DISCUSSION
in previous reports it was proposed that sustained postural tremor experimentally reproduced in monkeys (Ward, McCulloch and Magoun 1948: Poirier i960) implied the combined involvement of the nigrostriatal dopaminergic pathway (Poirier, Sourkes, Bouvier, Boucher and Carabin 1966) and the corresponding rubro-olivocerebelto-rubral loop (Larochelle, B6dard, Boucher and Poirier 1970: Poirier, Bedard, Langelier, Larochelle, Parent and Roberge 1972). The results of the present experiments confirm these observations (Fig. 8). As a matter of fact the laigrostriatal dopaminergic pathways are extensively and bilaterally interrupted in monkeys P1 and P2. The rubro-olivo-cerebello-rubral loop is also involved in both animals. Th~ latter structure, however, is extensively destroyed only on the right side in monkey P2 which, in contrast to PI, did not show tremor bilaterally but only in the opposite limbs. In these 2 animals apomorphine, a dopamine agonist thought to produce its effect by acting on dopamine receptors (Ernst 1967), completely abolished posturat tremor. The importance of the combined involvement of the 2 above-mentioned series of structures is further supported by the fact that extensive interruption of the nigrostriatal pathways in 4 other monkeys (P3-P6) did not result in tremor.
155 Rigidity as previously observed in 2 monkeys (Poirier 1960) was associated with the cog-wheel phenomenon in the four limbs of monkey PI and in the left limbs of monkey P2. In monkey PI the lesions extensively damage the nigrostriatal pathway, the parvocellular division of the red nucleus and cerebellothalamic fibers on both sides of the brain stem (Fig. 8, Table 1). In monkey P2 the lesions interrupt the nigrostriatal pathways on both sides and extensively destroy the parvocellular division of the red nucleus and corresponding cerebellothalamic fibers on the right side. These results are in contradistinction to the findings of earlier studies in which most animals displayed hypotonicity of the limbs following ventromedial tegmental lesions (Poirier 1960; Poirier et al. 1966, 1969, 1972). Under such conditions, however, the hypotonicity of the limbs was associated with lesions that extended more caudally than in monkeys P1 and P2 and destroyed in addition to the above-mentioned structures the magnocellular division of the red nucleus and corresponding rubrotegmentospinal nervous fascicles. In the light of these data it seems conceivable that Parkinsonian-like rigidity is a consequence of the combined involvement of the nigrostriatal pathway and the homolateral parvocellular division of the red nucleus and/or ascending cerebellothalamic fibers but its appearance most likely necessitates the integrity of the corresponding magnocellular division of the red nucleus and rubrotegmentospinal tract. In this regard it is worth recalling that the interruption of the spinal sensory roots in man (Pollock and Davis 1930) and monkeys (Ohy6, Bouchard, Larochelle, B6dard, Boucher, Raphy and Poirier 1970) does not abolish postural tremor but results in hypotonicity of the corresponding limb. The fact that apomorphine and piribedil, dopamine agonists, reverse this type of hypertonicity supports the idea that the loss of the nigrostriatal DA mechanism plays an important role in the production of rigidity. Akinesia, in addition to tremor and rigidity, was also observed in monkeys P1 and P2 following the lesions described above. Severe akinesia also developed in 4 other monkeys (P3-P6) of this series following bilateral lesions which in the main destroyed structures located rostrally at the base of the midbrain. The type of akinesia observed in these animals is quite similar to the behaviour described in cats by Ranson and lngram (1932) and in monkeys by Ranson (1939) and Collins (1954) following bilateral lesions placed at level of the rostral midbrain and/or caudal hypothalamus. Such lesions bilaterally destroy monoaminergic nervous fibers including the nigrostriatal pathways but spare the pallidofugal fibers. In the light of these and previous data (Poirier 1960) it appears that the most important structures involved in the production of akinesia of this type are located within the ventromedial area at upper midbrain level. This area is known to contain important monoaminergic pathways ending in various structures of the midbrain, diencephalon and telencephalon (Heller, Harvey and Moore 1962; Anden, Dahlstr6m, Fuxe and Larsson 1965; Poirier and Sourkes 1965). As shown above bilateral lesions involving the basomedial area of Tsai result in akinesia. A similar type of akinesia may be pharmacologically induced by administering alpha-methyl-p-tyrosine (AMT) or reserpine (Carlsson, Lindqvist and Magnusson 1957; B6dard, Larochelle, Poirier and Sourkes 1970; Larochelle, B6dard, Poirier and Sourkes 1971) known to interfere with the metabolism of brain
156 m o n o a m i n e s . In view o f these facts it is conceivable t h a t the akinesia asstwiated wit h bilateral lesions o f the rostral m i d b r a i n results from the loss o f c a t e c h o i a m i n e r g i c ( C A ) p a t h w a y s , a c o n d i t i o n which may be c o m p a r e d to the decrease ~'n c a t e c h ( + a m i n e c o n c e n t r a t i o n f o u n d in the brains o f P a r k i n s o n i a n patients (Ehringer and H o r n y k i e w i c z 1960). in this regard the nigrostriatal D A mechanisms N a y an imp o r t a n t but not exclusive role in the m a i n t e n a n c e o f m o t o r activity. ~Xn a h n o s t c o m p l e t e exclusion o f the influence o f the striopallidat system on o t h e r C N S mechanisms (as achieved by i n t e r r u p t i o n o[" the outflow o f this system and ~,,I ihe nigr,:striatal p a t h w a y s at h y p o t h a l a m i c level in m o n k e y s P7, P8 and P9 ol ~ '~his ~cries) results only in b r a d y k i n e s i a . O t h e r C A p a t h w a y s coursing at the base o f the m i d b r a i n and ending in the rostral structures o f the brain seem to be also invol~cd. F u r t h e r w o r k is needed to establish the rclative c o n t r i b u t i o n o f the DA striatal m e c h a n i s m : and o f other C A mechanisms (located in the u p p e r brain stem and telencephalic structures) to the initiation and p e r f o r m a n c e o f purposeful movemenl,;. In this respect H o p k i n s and Lawrence (I 975) recently reported that an i m p o r t a n t n u m b e r oi ~ nervous fibers, most likely from nigral origin, leave the nigrostriatal traci a~ the level o f the p a r v o c e l l u l a r red nucleus and s u b t h a l a m i c nucleus and cross tl~e internal capsule and p a l l i d u m before ending in the h o m o l a t e r a l n e o s t r i a t u m (see lheir Fig. 8i. This observation may prove to be i m p o r t a n t in assessing the m a r k e d difference o~ b e h a v i o r i m p a i r m e n t between m o n k e y s with bilateral a n d b a s o m e d i a l lesions ,,t" the p r e m a m i l l a r y h y p o t h a l a m i c a r e a and m o n k e y s with bilateral a n d b a s o m c d t a i lesion.~ o f the m e s e n c e p h a l o - h y p o t h a l a m i c .junctional area, respectively. F i n a l l y ti~e integrily o f the pallidofugal fibers from the internal division o f the pallidum a n d the ~'~rresponding p a l l i d o t h a l a m i c fibers represents an essential feature for the i m p r o v e m e n t o i akinesia by D A agonists as suggested by the evidence that a p o m o r p h i n c nol onl'~ does not i m p r o v e b r a d y k i n e s i a in m o n k e y s with a bilateral i n t e r r u p t i o n c,! the palJido|'ugal fibers (P7, P8 a n d P9) but renders these animals p r o s t r a t e d .
REFERENCES Anden, N.-E., A. Dahlstr6m, K. Fuxe and K. Larsson (1965) Further evidence tk~rtl~e presence of nigro-neostriatal dopamine neurons in the rat, Auwr. ,t. Anat., 116: 329-333. B6dard, P., L. Larochelle, L. J. Poirier and T. L. Sourkes (1970) Reversible effect oi ]-DOPA on tremor and catatonia induced by ~t-methyl-p-tyrosine, Canad. J. physiol. Pharmacist., 48: 82~84. Carlsson, A., M. Lindqvist and T. Magnusson (1957) 3,4-Dihydroxyphenylalanine trod 5-hydroxytryptophan as reserpine antagonists, Nature (Lond.), 180: 1200. Collins, E. H. (1954) Localization of an experimental hypothalamic and rnidbram ssndrome simulating sleep, J. comp. Neurol., 100:661 690. Ehringer, H. and O. Hornykiewicz (1960) Verteilung yon Noradrenalin und Dopamine i3-Hydroxytyramin) im Gehirn des Menschen und ihr Verhalten bei Erkrankungen des extrapyramidalen Systems, KI#l. Wschr., 38:1236 1239. Ernst, A. M. (1967) Mode of action of apomorphine and dexamphetamine on gnawing compulsion in rats, Ps;vehopharmacologia (Berl.), 10:316 323. Filion, M., k. Larochelle and L. J. Poirier (1974) Globus pallidus unit activity in a monkey with a parkinson-like syndrome. - Effect of apomorphine, Clin. Res., 22: 754A (Abstract). Heller, A., J. Harvey and R. Moore (1962) A demonstration of a fall in brain serotonin following central nervous system lesion in the rat, Biochem. Pharmacol., 11 : 859-866. Hopkins, D. A. and D. G. Lawrence (1975) On the absence of a rubrothalamic prt~jection in the
157 monkey with observations on some ascending mesencephalic projections, J. comp. Neurol., 161 : 269-293. Larochelle, L., J. C. P6chadre and L. J. Poirier (1974) Parkinson's syndrome An experimental model, Clin. Res., 22: 755A (Abstract). Larochelle, L., P. B6dard, R. Boucher and L. J. Poirier (1970) The rubro-olivo-cerebello-rubral loop and postural tremor in the monkey, J. neurol. Sci., 11 : 53-64. Larochelle, L., P. Bddard, L. J. Poirier and T. L. Sourkes (1971) Correlative neuroanatomical and neuropharmacological study of tremor and catatonia in the monkey, Neuropharmaeology, 10: 273-288. Ohy6, C., R. Bouchard, L. Larochelle, P. B6dard, R. Boucher, B. Raphy and L. J. Poirier (1970) Effect of dorsal rhizotomy on postural tremor in the monkey, Exp. Brain Res., 10: 140-150. Poirier, L. J. (1960) Experimental and histological study of midbrain dyskinesias, J. Neurophysiol., 23:534 551. Poirier, L. J. and T. L. Sourkes (1965) Influence of the substantia nigra on the catecholamine content of the striatum, Brain, 88:181 182. Poirier, L. J., M. Filion, P. Langelier and L. Larochelle (1975) Brain nervous mechanisms involved in the so-called extrapyramidal motor and psychomotor disturbances, Progress in Neurobiol., 5, Part I: 197-244. Poirier, L. J., T. L. Sourkes, G. Bouvier, R. Boucher and S. Carabin (1966) Striatal amines, experimental tremor and the effect of harmaline in the monkey, Brain, 89: 37-52. Poirier, L. J., P. B6dard, P. Langelier, L. Larochelle, A. Parent and A. G. Roberge (1972), Les circuits neuronaux impliquds dans la physiopathologie des syndromes parkinsoniens, Rev. neurol., 127:37 50. Poirier, L. J., G. Bouvier, P. B6dard, R. Boucher, L. Larochelle, A. Olivier and P. Singh (1969) Essai sur les circuits neuronaux impliqu6s dans le tremblement postural et l'hypokindsie, Rev. neurol., 120:15 40. Pollock, L. J. and L. Davis (1930) Muscle tone in parkinsonian states, Arch. Neurol. P~yehiat. (Chic.), 23:303 319. Ranson. S. W. (1939) Somnolence caused by hypothalamic lesions in the monkey, Arch. Neurol. Psyehiat. (Chic.), 41: 1-23. Ranson, S. W. and W. R. Ingram (1932) Catalepsy caused by lesions between the mammillary bodies and ill nerve in the cat. Amer. J. Physiol., 101 : 690-696. Ward, Jr., A. A., W. S. McCulloch and H. W. Magoun (1948) Production of an alternating tremor at rest in monkeys, J. Neurophysiol., I1: 317-330.
147
© Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
P A R K I N S O N I A N AKINESIA, R I G I D I T Y A N D T R E M O R IN T H E M O N K E Y Histopathological and Neuropharmacological Study
J. C. PI~CHADRE*, L. LAROCHELLE** AND L. J. PO1RIER
Laboratoires de Neurobiologie, Facultd de M6decine, Universit~Laval, Quebec, P. Q. G I K 7P4 (Canada) (Received 28 August, 1975)
SUMMARY
Parkinsonian postural tremor and rigidity most likely involve the disruption of the dopaminergic (DA) nigrostriatal mechanisms and the corresponding rubroolivo-cerebello-rubral loop without excluding the involvement of related dentatorubral and dentato-thalamic nervous fascicles. The integrity of the magnocellular division of the red nucleus and of the rubrotegmentospinal pathway, however, is apparently essential for the expression of rigidity. Akinesia most likely results from the bilateral involvement of brain stem catecholaminergic (CA) mechanisms including the DA nigrostriatal pathways. Finally the integrity of the pallidothalamic fibers seems to represent an essential feature for the improvement of these motor disorders by DA agonists, suggesting that certain of these agents, such as apomorphine, exert their main effects through the neostriatal DA receptors.
INTRODUCTION
In a previous study (Poirier 1960) the most characteristic motor disturbances of Parkinsonism, akinesia, rigidity and tremor, had been reproduced by upper brain stem tegmental lesions in 2 monkeys. Other animals described in the same paper (Poirier 1960) and in another report (Poirier, Bouvier, B6dard, Boucher, Larochelle, Olivier and Singh 1969), however, displayed sustained postural tremor most often associated with hypotonicity and hypokinesia of one or several limbs following somewhat differently placed lesions. This work was supported by the Medical Research Council of Canada. * Supported by the Quebec Medical Research Council. ** Scholar of Medical Research Council of Canada,
148 A-SPONTANEOUS
TREMOR
Biceps
Triceps
sec
B- P A S S I V E .......
MOVEMENTS
FL EX~O N - - - ' ~ "
. . . .
EXTENSLON .........
-{--
~:L ~ × I O N . . . .
Triceps
C - - J sec
Fig. I. Electromyographic recordings in monkes, PI show,ing tremor and rigidity: ,4: spontaneou~ rhythmic bursts of EMG activity al a fiequency close Io 7/s and alternating in the biceps arid triceps muscles; B: rigidity is evidenced by the strong reflex activity in the stretched muscles. A cog-wheel phenomenon, also experienced clinically during passive movements is evidenced by the rhythnlic bursts, at the frequency of tremor, displayed by the stretched muscles.
Fig. 2.
149
Fig. 3.
Figs. 2-4. Transverse sections through upper brain stem of monkey P1 illustrating bilateral lesions involving the caudal hypothalamus, medial subthalamus and rostral midbrain (2-3). Fig. 4 represents a transverse section through caudal midbrain to show sparing of the magnocellular division of the red nucleus. Note also almost total cell loss in both substantia nigra. L, lesion; RN, red nucleus, magnocellular division; SN, substantia nigra. Basic fuchsin and fast blue, >: 7, x 7 and ×20, respectively.
150
In the present study we succeeded in reproducing akinesia, rigidity (assocmted with the cog-wheel phenomenon) and tremor in 2 other monkeys and akinesia or bradykinesia in several other monkeys following bilateral upper brain stem tegmental lesions. Moreover neuropharmacological data obtained in these animals together with the histopathological findings permit us to arrive to more specific conclusions concerning the mechanisms involved in these types of motor disorders. Certain results including electrophysiological data obtained in one animal of this series (Pl) were published in preliminary notes (Filion, Larochelle and Poirier 1974; Larochclte, Pdchadre and Poirier 1974) and a review article (Poirier, Filion, Langelier and Larochelle 1975). MATERIAL AND METHODS
In all 9 animals of this series the lesions were produced, under pentobarbital anesthesia, by electrocoagulation using a high-frequency current directed tilrough a monopolar electrode stereotaxically introduced in the brain. Postoperatively the animals were regularly observed and the effects of either apomorphine, tevodopa or piribedil (ET-495, Laboratoires Servier, Orl6ans), all of which are ciopamine agonists, on the motor disturbances were tested. Their behavior was cinematographically recorded and EMGs of the tremor-affected and hypertonic muscles were made, EMGs were taken with copper wires introduced into tile muscles through hypodermic needles. A Gould pen recorder (Model 440) was used for recording the EMG aclivity The animals were killed by an overdose of pentobarbital and their brains were fixed in a solution of 10 °~i neutral formalin. Serial sections of the brains were prepared and stained with basic fuchsin and fast blue. RESULTS
Akinesia, rigidity and tremor (monkeys Pl and P2~ Following incomplete lesions of the cerebellar dentate nuclei monkey PI did not show any detectable motor impairment. Nine months later bilateral tegmental lesions (the 2 lesions made 10 days apart) were produced Following these lesions the animal gradually (within 5 days) became aphagic, profoundly akinetic and displayed postural tremor and rigidity of the four limbs. Rigidity characterized by increased resistance to passive movements was associated with the cog-wheel phenomenon in the 4 limbs (Fig. I). He had tc be force-fed daily and the motor disturbances remained unchanged during the whole 9 weeks postoperative period. The administration of a single dose of levodopa (30 mg/kg, i.p.) produced no noticeable effect on the motor impairments whereas the injection of apomorphine ~0.0150.2 mg/kg, i.m.) or piribeOil ( 1.5-2.5 mg/kg, i.m.) repeatedly counteracted the abovedesclibed motor disturbances for a 30-90 min period. Under such conditions the animal ran and ate spontaneously and the tremor and rigidity of the limbs vanished. In this animal (P 1) the bilateral brain stem lesions involve the ventromedial tegmental area of the upper midbrain, tile caudal part of the hypothalamus and the medial
151 TABLE
1
STRUCTURES
Monkeys
EXTENSIVELY
Red
nucelus
M
P
INVOLVED
Cere
AND
Nigrostriatal
bello- fibers fugal fibers m i d brain
ASSOCIATED
Pallido-
Tremor
MOTOR
DISTURBANCES
Rigidity
AkinesiaBrady-
fugal
kinesia
fibers
hypothalamus
P1
--
B
B
B
B
--
B
B
Pr
P2
--
R
R
B
--
--
L
L
Pr
---
P3
--
R
B
B
Ab
Ab
Pr
--
P4
--
--
--
B
R
--
Ab
Ab
Pr
--
P5
--
--
--
B
--
--
Ab
Ab
Pr
--
P6
--
--
B
B
--
Ab
Ab
Pr
--
P7
--
L
--
B
B
Ab
Ab
--
Pr
P8
--
--
--
B
B
Ab
Ab
--
Pr
P9
--
--
--
B
B
Ab
Ab
--
Pr
Ab
=
absent;
of red nucleus;
B = Pr
bilateral; =
L, R =
left and
right;
M, P =
magnocellular
and
parvocellular
division
present.
part of the subthalamus (Figs. 2 and 3). The lesions which are very close to the interpeduncular fossa at upper midbrain level are associated with an almost complete degeneration of the neurons of the substantia nigra and nuclei paranigralis, linearis and parabrachialis pigmentosus on both sides. More dorsally, the lesions destroy most of the parvocellular division of the red nuclei and interrupt corresponding cerebellothalamic fibers. The magnocellular division of the red nuclei and corresponding rubral and tegmental descending pathways, however, are spared (Fig. 4). At diencephalic level the lesions destroy most of the structures in the caudal third of the hypothalamus and the more medially located structures of the subthalamus sparing, however, most of the subthalamic nucleus and the pallidothalamic fibers corresponding to Forel's H fields (Fig. 2). The neurons of both divisions of the pallidum are apparently normal (Table 1). Monkey P2 also became gradually akinetic but not aphagic following the production of bilateral tegmental lesions (the 2 lesions made 8 days apart). The akinesia was associated with postural tremor and rigidity (including the cog-wheel phenomenon) of the left limbs. These motor disturbances which were present during the whole postoperative period of 4 weeks were counteracted by apomorphine (0.2 mg/kg, i.m.). In this animal the lesions extending close to the interpeduncular fossa bilaterally involve the ventromedial tegmental area of the upper midbrain. They resulted in almost total cell losses of the substantia nigra and nuclei paranigralis, linearis and parabrachialis pigmentosus. In addition the parvocellular division of the red nucleus and ascending cerebellothalamic fibers are extensively destroyed on the right side and very slightly damaged on the left side. The magnocellular division of the red nucleus, the rubrotegmentospinal tract as well as the hypothalamus and subthalamus are spared on both sides (Fig. 5, Table 1).
152
l-ig. 5. l-ransverse scctioi? lhrough upper brain slem of T~loi~kcy P2 lo illustrate sparing ol cauda hvpothalamus and subthalamus. Same slain. 7
Fig. 6. Transverse section through upper midbram of monkey 1'6 to illustrate bilateral veJ~tromedia tegmental lesions. Same stain, 7.
153
Fig. 7. Transverse section through diencephalon of monkey P7 showing bilateral and extensive lesions involving the hypothalamus and medial subthalamus. Note extensive destruction of Ford's H fields. Same stain, × 7.
Akinesia and prostration (monkeys P3-P6) Four other monkeys survived 14 (P3 and P4), 6 (P5) and 7 days (P6), respectively, following bilateral tegmental lesions (the 2 lesions made a few days apart). All 4 animals which were relatively alert and active and ate spontaneously in the immediate postoperative days gradually became profoundly akinetic and aphagic and finally prostrated and died. They did not show any tremor or rigidity of the limbs. Apomorphine (0.2 mg/kg, i.m.) tested in only one of these 4 monkeys (P3) one week after the operation transiently rendered the animal more active. He spontaneously ate and drank. In all 4 animals the bilateral lesions involve the ventromedial part of the rostral midbrain and impinge on the medial part of the subthalamus (Fig. 6). The hypothalamus (at the level of the caudal part of the mamillary body) is invaded bilaterally in two monkeys (P3, P6), and unilaterally in another monkey (P4) (Table l). Bradykinesia (monkeys P7-P9) Three other monkeys (P7, P8, P9) became bradykinetic following bilateral brain stem lesions of the hypothalamus which spared the midbrain. When attacked, however, they ran away. Neither tremor nor rigidity was present Jn these two animals, Apomorphine (0.4 mg/kg, i.m.) did not improve bradykinesia in contrast to the effect of this drug on akinesia in monkeys P1, P2 and P3. On the contrary the 3 animals froze instead of showing signs of hyperexcitability usually observed in other monkeys.
154
THALAMUS VA VL
•
\."x2. HYPOTHALAMU~
,. GLOBUS i PALLIDUS
PARVO RED NUCLEUS MAGNC
%
CEREBELLUM
/
SUBSTANTIA NIGRA
i d ~ I N F . OLIVE Fig. 8. Schematic drawing Io illustrate the main nervous structures bilaterally involved in monkey PI that showed sustained akinesia, rigidity and tremor. They include the parvoceltular division of the red nucleus and corresponding rubro-olivary fibers, the nigrostriatal pathway and cerebello-thalamic and cerebello-rubral ascending fibers.
The lesions in these 3 animals, as illustrated on Fig. 7, bilateraity destroy most of the structures at the level of the caudal hypothalamus including the nigrostriatal pathways. Moreover at the level of Ford's H fields they completely and bilaterally interrupt the pallidofugal fibers (Table 1). DISCUSSION
in previous reports it was proposed that sustained postural tremor experimentally reproduced in monkeys (Ward, McCulloch and Magoun 1948: Poirier i960) implied the combined involvement of the nigrostriatal dopaminergic pathway (Poirier, Sourkes, Bouvier, Boucher and Carabin 1966) and the corresponding rubro-olivocerebelto-rubral loop (Larochelle, B6dard, Boucher and Poirier 1970: Poirier, Bedard, Langelier, Larochelle, Parent and Roberge 1972). The results of the present experiments confirm these observations (Fig. 8). As a matter of fact the laigrostriatal dopaminergic pathways are extensively and bilaterally interrupted in monkeys P1 and P2. The rubro-olivo-cerebello-rubral loop is also involved in both animals. Th~ latter structure, however, is extensively destroyed only on the right side in monkey P2 which, in contrast to PI, did not show tremor bilaterally but only in the opposite limbs. In these 2 animals apomorphine, a dopamine agonist thought to produce its effect by acting on dopamine receptors (Ernst 1967), completely abolished posturat tremor. The importance of the combined involvement of the 2 above-mentioned series of structures is further supported by the fact that extensive interruption of the nigrostriatal pathways in 4 other monkeys (P3-P6) did not result in tremor.
155 Rigidity as previously observed in 2 monkeys (Poirier 1960) was associated with the cog-wheel phenomenon in the four limbs of monkey PI and in the left limbs of monkey P2. In monkey PI the lesions extensively damage the nigrostriatal pathway, the parvocellular division of the red nucleus and cerebellothalamic fibers on both sides of the brain stem (Fig. 8, Table 1). In monkey P2 the lesions interrupt the nigrostriatal pathways on both sides and extensively destroy the parvocellular division of the red nucleus and corresponding cerebellothalamic fibers on the right side. These results are in contradistinction to the findings of earlier studies in which most animals displayed hypotonicity of the limbs following ventromedial tegmental lesions (Poirier 1960; Poirier et al. 1966, 1969, 1972). Under such conditions, however, the hypotonicity of the limbs was associated with lesions that extended more caudally than in monkeys P1 and P2 and destroyed in addition to the above-mentioned structures the magnocellular division of the red nucleus and corresponding rubrotegmentospinal nervous fascicles. In the light of these data it seems conceivable that Parkinsonian-like rigidity is a consequence of the combined involvement of the nigrostriatal pathway and the homolateral parvocellular division of the red nucleus and/or ascending cerebellothalamic fibers but its appearance most likely necessitates the integrity of the corresponding magnocellular division of the red nucleus and rubrotegmentospinal tract. In this regard it is worth recalling that the interruption of the spinal sensory roots in man (Pollock and Davis 1930) and monkeys (Ohy6, Bouchard, Larochelle, B6dard, Boucher, Raphy and Poirier 1970) does not abolish postural tremor but results in hypotonicity of the corresponding limb. The fact that apomorphine and piribedil, dopamine agonists, reverse this type of hypertonicity supports the idea that the loss of the nigrostriatal DA mechanism plays an important role in the production of rigidity. Akinesia, in addition to tremor and rigidity, was also observed in monkeys P1 and P2 following the lesions described above. Severe akinesia also developed in 4 other monkeys (P3-P6) of this series following bilateral lesions which in the main destroyed structures located rostrally at the base of the midbrain. The type of akinesia observed in these animals is quite similar to the behaviour described in cats by Ranson and lngram (1932) and in monkeys by Ranson (1939) and Collins (1954) following bilateral lesions placed at level of the rostral midbrain and/or caudal hypothalamus. Such lesions bilaterally destroy monoaminergic nervous fibers including the nigrostriatal pathways but spare the pallidofugal fibers. In the light of these and previous data (Poirier 1960) it appears that the most important structures involved in the production of akinesia of this type are located within the ventromedial area at upper midbrain level. This area is known to contain important monoaminergic pathways ending in various structures of the midbrain, diencephalon and telencephalon (Heller, Harvey and Moore 1962; Anden, Dahlstr6m, Fuxe and Larsson 1965; Poirier and Sourkes 1965). As shown above bilateral lesions involving the basomedial area of Tsai result in akinesia. A similar type of akinesia may be pharmacologically induced by administering alpha-methyl-p-tyrosine (AMT) or reserpine (Carlsson, Lindqvist and Magnusson 1957; B6dard, Larochelle, Poirier and Sourkes 1970; Larochelle, B6dard, Poirier and Sourkes 1971) known to interfere with the metabolism of brain
156 m o n o a m i n e s . In view o f these facts it is conceivable t h a t the akinesia asstwiated wit h bilateral lesions o f the rostral m i d b r a i n results from the loss o f c a t e c h o i a m i n e r g i c ( C A ) p a t h w a y s , a c o n d i t i o n which may be c o m p a r e d to the decrease ~'n c a t e c h ( + a m i n e c o n c e n t r a t i o n f o u n d in the brains o f P a r k i n s o n i a n patients (Ehringer and H o r n y k i e w i c z 1960). in this regard the nigrostriatal D A mechanisms N a y an imp o r t a n t but not exclusive role in the m a i n t e n a n c e o f m o t o r activity. ~Xn a h n o s t c o m p l e t e exclusion o f the influence o f the striopallidat system on o t h e r C N S mechanisms (as achieved by i n t e r r u p t i o n o[" the outflow o f this system and ~,,I ihe nigr,:striatal p a t h w a y s at h y p o t h a l a m i c level in m o n k e y s P7, P8 and P9 ol ~ '~his ~cries) results only in b r a d y k i n e s i a . O t h e r C A p a t h w a y s coursing at the base o f the m i d b r a i n and ending in the rostral structures o f the brain seem to be also invol~cd. F u r t h e r w o r k is needed to establish the rclative c o n t r i b u t i o n o f the DA striatal m e c h a n i s m : and o f other C A mechanisms (located in the u p p e r brain stem and telencephalic structures) to the initiation and p e r f o r m a n c e o f purposeful movemenl,;. In this respect H o p k i n s and Lawrence (I 975) recently reported that an i m p o r t a n t n u m b e r oi ~ nervous fibers, most likely from nigral origin, leave the nigrostriatal traci a~ the level o f the p a r v o c e l l u l a r red nucleus and s u b t h a l a m i c nucleus and cross tl~e internal capsule and p a l l i d u m before ending in the h o m o l a t e r a l n e o s t r i a t u m (see lheir Fig. 8i. This observation may prove to be i m p o r t a n t in assessing the m a r k e d difference o~ b e h a v i o r i m p a i r m e n t between m o n k e y s with bilateral a n d b a s o m e d i a l lesions ,,t" the p r e m a m i l l a r y h y p o t h a l a m i c a r e a and m o n k e y s with bilateral a n d b a s o m c d t a i lesion.~ o f the m e s e n c e p h a l o - h y p o t h a l a m i c .junctional area, respectively. F i n a l l y ti~e integrily o f the pallidofugal fibers from the internal division o f the pallidum a n d the ~'~rresponding p a l l i d o t h a l a m i c fibers represents an essential feature for the i m p r o v e m e n t o i akinesia by D A agonists as suggested by the evidence that a p o m o r p h i n c nol onl'~ does not i m p r o v e b r a d y k i n e s i a in m o n k e y s with a bilateral i n t e r r u p t i o n c,! the palJido|'ugal fibers (P7, P8 a n d P9) but renders these animals p r o s t r a t e d .
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