Exp Brain Res (1992) 91:236-248
Experimental BrainResearch 9 Springer-Verlag1992
Low-threshold, short-latency cutaneous reflexes during fictive locomotion in the "semi-chronic" spinal cat Lisa A. LaBella, Andrzej Niechaj, and Serge Rossignol Centre de Recherche en Sciences Neurologiques, Facult6 de M6decine, Universit6 de Montr6al, C.P. 6128, Succ. A, Montr6al, Qu6bec, Canada H3C 3J7 Received May 9, 1991 / Accepted April 8, 1992
Summary. Low-threshold, short-latency cutaneous reflexes evoked in ipsilateral hindlimb m o t o r nerves were examined during fictive locomotion. Locomotion in 11 anaemically decerebrated spinal animals (1-3 weeks after transection at T13-L1) was induced by administration of clonidine, L-dopa and nialamide; by administration of the latter two drugs only; or by exteroceptive stimulation in the absence o f any drugs. The caudal and lateral cutaneous sural, caudal cutaneous femoral, saphenous and superficial peroneal nerves were stimulated at low threshold (1.5-3 T). Pooled results from all combinations of cutaneous nerves stimulated and muscle nerves recorded show that the initial response was excitatory in 40 of 50 triceps surae and 17 of 20 semitendinosus (St) electroneurograms (ENGs). These excitatory responses occurred at latencies that ranged from 5 to 15 ms and tended to be maximal during the m o t o r nerve's active period in the step cycle (i.e. they were modulated in a phase-dependent manner). Only three inhibitory responses (9-12 ms earliest latency) were encountered in total: in two St E N G s o f one animal and in one lateral gastrocnemius-soleus E N G of a different animal. In two animals a "second" excitatory response (15-25 ms latency) was sometimes recorded in triceps surae and St nerves and, interestingly, could be modulated out of phase with the early response. Weak short-latency excitatory reflexes were also found in contralateral St ENGs when examined. Finally, among medial gastrocnemius, lateral gastrocnemius and soleus nerves, excitatory responses due to stimulation of any particular cutaneous nerve tended to be modulated similarly but were of consistently different amplitude among the three. This finding, together with the general observation that excitatory reflexes produced by stimulation of a particular cutaneous nerve were modulated similarly in extensors (or flexors) of different animals, suggests that spinal circuits generating locomotion may indeed exert a stereotypic control over interneurons in specific cutaneous reflex pathways to motoneurons. The results are primarily discussed in Correspondence to: S. Rossignol
terms of the existing evidence for short-latency excitatory cutaneous reflexes in extensors in a variety of locomotive and non-locomotive preparations.
Key words: Cutaneous reflexes
Fictive locomotion Electroneurography - Semi-chronic spinal cat
Introduction Excitatory reflexes to flexors or extensors, evoked by stimulation of low-threshold cutaneous afferents, have been shown to undergo modulation during different phases of the locomotor step cycle. Such modulation has been seen in intact cats (Duysens and Stein 1978; Forssberg 1979; Duysens and Loeb 1980; Abraham et al. 1985; Drew and Rossignol 1987) and decerebrate animals (Duysens and Pearson 1976). The demonstration of such phase dependency in both walking spinal cats (Forssberg et al. 1975, 1977) and acute (Andersson et al. 1978; Schomburg and Behrends 1978; Schmidt et al. 1988, 1989) or chronic (Andersson et al. 1978) spinal cats during fictive locomotion strongly suggests that, in addition to certain inhibitory spinal interneurons (see Pratt and Jordan 1987), excitatory interneurons in segmental reflex pathways may be phasically driven by the spinal central pattern generator for locomotion. Evidence for such phasic control over excitatory cutaneous reflex pathways, however, may be strongest for pathways to flexor motoneurons. For example, with spinal cats walking on a treadmill, the most c o m m o n observation has been excitatory responses in flexors if the stimulus is applied during swing, but a mix o f excitatory and inhibitory responses in extensors if the stimulus is applied during stance (for review see Rossignol et al. 1988). Studies that have recorded directly from motoneurons during fictive locomotion have reported similar results. One investigation reported evidence for phase-dependent cutaneous-evoked excitatory postsynaptic potentials (EPSPs) in both flexor and extensor motoneurons but
237 f o u n d t h a t the m o d u l a t i o n in e x t e n s o r s was less pronounced and that patterns of modulation "varied s u b s t a n t i a l l y b e t w e e n different cells o f the s a m e species" ( A n d e r s s o n et al. 1978). T w o o t h e r studies r e p o r t e d clear evidence p r i m a r i l y for flexor m o t o n e u r o n s , w i t h m o r e v a r i a b l e results ( S c h o m b u r g a n d B e h r e n d s 1978) o r little evidence ( S c h m i d t et al. 1989) for p h a s e d e p e n d e n c y in extensor motoneurons. A more recent study (Mosc h o v a k i s et al. 1991) has s h o w n t h a t t w o s h o r t - l a t e n c y c u t a n e o u s p a t h w a y s giving e x c i t a t i o n to flexor d i g i t o r u m l o n g u s ( F D L ) m o t o n e u r o n s were c o n t r o l l e d differentially in the o p p o s i t e p h a s e o f the fictive l o c o m o t o r cycle. T h e superficial p e r o n e a l (SP) nerve gave e x c i t a t i o n to F D L d u r i n g flexion w h e n it was n o r m a l l y active, while the m e d i a l p l a n t a r nerve excited F D L m o t o n e u r o n s o n l y w h e n it also d i s c h a r g e d d u r i n g the e x t e n s o r phase. T h e a p p a r e n t i n c o n s i s t e n c i e s in r e s p o n s e s o f e x t e n s o r s to c u t a n e o u s s t i m u l a t i o n d u r i n g l o c o m o t i o n is puzzling, since c u t a n e o u s p r o j e c t i o n s to e x t e n s o r m o t o n e u r o n s h a v e l o n g b e e n d e s c r i b e d ( W i l s o n 1963; C o l e b a t c h a n d Gillies 1979). T w o r e c e n t i n t r a c e l l u l a r studies using n o n l o c o m o t i n g p r e p a r a t i o n s s u p p o r t the e a r l y suggestion o f H a g b a r t h (1952) t h a t h i n d l i m b e x t e n s o r m o t o r nuclei are p r e f e r e n t i a l l y excited b y c u t a n e o u s nerves a r i s i n g f r o m m o r e c i r c u m s c r i b e d s k i n regions t h a n is the case for flexor m o t o n e u r o n p o o l s . F o r e x a m p l e , in the first o f these studies, triceps s u r a e m o t o r nuclei - d e s p i t e b e i n g close f u n c t i o n a l synergists - were s h o w n to receive differential e x c i t a t o r y i n p u t f r o m each o f the two c u t a n e o u s sural nerves ( L a B e l l a et al. 1989). I n the s e c o n d s t u d y , in w h i c h five h i n d l i m b c u t a n e o u s nerves were tested, m e d i a l g a s t r o c n e m i u s m o t o n e u r o n s were s h o w n to receive p o t e n t a n d c o n v e r g e n t e x c i t a t o r y i n p u t f r o m t w o nerves w i t h n e a r b y o r o v e r l a p p i n g receptive fields (the c a u d a l c u t a n e o u s sural ( C C S ) a n d c a u d a l c u t a n e o u s f e m o r a l ( C C F ) n e r v e s ; L a B e l l a a n d M c C r e a 1990). T h e q u e s t i o n p r e s e n t l y a d d r e s s e d is w h e t h e r o r n o t a clear (i.e. consistent) p h a s e d e p e n d e n c y o f e x c i t a t o r y c u t a n e o u s reflexes in e x t e n s o r s d u r i n g fictive l o c o m o t i o n will e m e r g e if we focus o u r s t u d y o n triceps s u r a e a n d s t i m u l a t e c u t a n e o u s nerves w h i c h are k n o w n to p r o d u c e l o w - t h r e s h o l d excitation in triceps s u r a e m o t o n e u r o n s (see L a B e l l a et al. 1989 a n d L a B e l l a a n d M c C r e a 1990). A s this r e p o r t describes, in a d d i t i o n to e x c i t a t o r y c u t a n e o u s reflexes r e c o r d e d in h i n d l i m b flexor nerves o f spinal cats (1 3 w e e k s p o s t t r a n s e c t i o n ) , t h o s e e v o k e d in the a n k l e e x t e n s o r nerves also u n d e r g o c o n s i s t e n t p h a s e d e p e n d e n t m o d u l a t i o n d u r i n g the fictive step cycle. F u r t h e r m o r e , w i t h o n l y s o m e exceptions, these reflexes are e n h a n c e d d u r i n g the p h a s e o f the cycle in w h i c h the nerves a r e t y p i c a l l y active ( A n d e r s s o n et al. 1978; S c h o m b u r g a n d B e h r e n d s 1978), a l t h o u g h the p e r i o d o f i n c r e a s e d reflex r e s p o n s i v e n e s s does n o t strictly last t h r o u g h o u t the p e r i o d o f l o c o m o t o r activity. Materials and methods The aim of the experiments was to characterize short-latency responses to cutaneous nerve stimulation during fictive locomotion in the spinal cat. Normally, the adequate subject for such studies would be the acute spinal cat injected with nialamide and L-dopa
(Grillner and Zangger 1979; Schmidt et al. 1989). We have recently shown, in cats spinalized 1-2 weeks prior to the acute experiment, that fictive locomotion was sometimes evoked without drugs and also that, with clonidine only or L-dopa, locomotion was altogether easier to evoke and had a fi'equency more similar to the normal than in acutely spinalized cats (Pearson and Rossignol 1991). We have also shown that, as a function of time after spinalization, the fictive locomotor pattern becomes progressively more complex and expresses more features characteristic of the normal locomotor pattern. These facts led us to use animals (n = 11 ; mean weight 3.2 kg) that had been spinalized 1-3 weeks prior to the acute experiments.
Spinalization procedure Spinal cords were transected using sterile techniques and with the animals under pentobarbital sodium anaesthesia (32 mg/kg intraperitoneally or intravenously). Rostral and caudal cord segments were completely separated by dissection with fine forceps under a dissecting microscope. Penicillin G was administered during the first postoperative week (100000 IU/day). Bladders were manually expressed daily. Although the animals were not exercised on a treadmill during the postspinalization period, they were free to move around in individual large cages covered with absorbent cardboard, which was changed regularly. Cats were examined daily, and all cats had recovered brisk hindlimb reflexes when pressing on the foot or air stepping at the time of the acute experiment.
Preparation for the acute experiment Animals were surgically prepared under steroid anaesthesia, using intravenous Saffan 12 mg/kg (alphaxalone 9 mg/kg and alpha* dolone acetate 3 mg/kg). A tracheotomy was performed and one carotid artery cannulated to monitor blood pressure. An intravenous cannula was placed in either a forelimb or jugular vein for drug and fluid administration as well as for slow infusion of a glucose/ bicarbonate buffer. Atropine (0.12 mg) was given subcutaneously, prednisolone sodium succinate (20 mg every few hours) intramuscularly. Animals were then anaemically decerebrated by ligating the remaining intact carotid artery and the basilar artery (rostral to the posterior inferior cerebellar artery), which was reached by opening the skull ventrally at the level of the tympanic bulla (Pollock and Davis 1923). This was usually followed by a marked rigidity of the forelimbs and in a few cases the animal had to be ventilated. Given the residual effects of the anaesthetics, there was usually some time to initiate the dissection of hindlimb nerves before paralysis [pancuronium bromide (Pavuton) 0.3 mg/kg] and automatic ventilation. Previous experiments using Saffan for minor surgery in otherwise intact cats showed that cats were wide awake and walking around about 3 h after a single dose. In the present experiments, recordings started more than 3 h after injection of Saffan. Several nerves of the left (ipsilateral) hindlimb were cut and dissected free of surrounding tissue for subsequent stimulation (cutaneous nerves) or recording (motor nerves) on bipolar hook electrodes or cuff electrodes made of polysyloxane polymer and used in a monopolar configuration (Julien and Rossignol 1982; Pearson and Rossignol 1991). Semitendinosus (St), medial gastrocnemius (MG) and lateral gastrocnemius-soleus (LGS) nerves were placed in cuff electrodes. In some experiments the soleus (Sol) branch of the LGS nerve was dissected away to allow independent recording from lateral gastrocnemius (LG) and Sol efferents (in cuff electrodes or on bipolar hooks). In some experiments the contralateral St (coSt) nerve was also recorded through a monopotar cuff electrode. Cutaneous nerves stimulated for the production of reflex effects in ipsitateral motor nerves include the CCS and lateral cutaneous sural (LCS) nerves; the long distal branch of the CCF nerve; the saphenous nerve (Saph), taken approximately 1 cm above the level of the knee; and the SP nerve dissected at the ankle. CCS, LCS and CCF were stimulated on bipolar hook electrodes; Saph and SP were stimulated through monopolar cuff electrodes.
238
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Experimental BrainResearch 9 Springer-Verlag1992
Low-threshold, short-latency cutaneous reflexes during fictive locomotion in the "semi-chronic" spinal cat Lisa A. LaBella, Andrzej Niechaj, and Serge Rossignol Centre de Recherche en Sciences Neurologiques, Facult6 de M6decine, Universit6 de Montr6al, C.P. 6128, Succ. A, Montr6al, Qu6bec, Canada H3C 3J7 Received May 9, 1991 / Accepted April 8, 1992
Summary. Low-threshold, short-latency cutaneous reflexes evoked in ipsilateral hindlimb m o t o r nerves were examined during fictive locomotion. Locomotion in 11 anaemically decerebrated spinal animals (1-3 weeks after transection at T13-L1) was induced by administration of clonidine, L-dopa and nialamide; by administration of the latter two drugs only; or by exteroceptive stimulation in the absence o f any drugs. The caudal and lateral cutaneous sural, caudal cutaneous femoral, saphenous and superficial peroneal nerves were stimulated at low threshold (1.5-3 T). Pooled results from all combinations of cutaneous nerves stimulated and muscle nerves recorded show that the initial response was excitatory in 40 of 50 triceps surae and 17 of 20 semitendinosus (St) electroneurograms (ENGs). These excitatory responses occurred at latencies that ranged from 5 to 15 ms and tended to be maximal during the m o t o r nerve's active period in the step cycle (i.e. they were modulated in a phase-dependent manner). Only three inhibitory responses (9-12 ms earliest latency) were encountered in total: in two St E N G s o f one animal and in one lateral gastrocnemius-soleus E N G of a different animal. In two animals a "second" excitatory response (15-25 ms latency) was sometimes recorded in triceps surae and St nerves and, interestingly, could be modulated out of phase with the early response. Weak short-latency excitatory reflexes were also found in contralateral St ENGs when examined. Finally, among medial gastrocnemius, lateral gastrocnemius and soleus nerves, excitatory responses due to stimulation of any particular cutaneous nerve tended to be modulated similarly but were of consistently different amplitude among the three. This finding, together with the general observation that excitatory reflexes produced by stimulation of a particular cutaneous nerve were modulated similarly in extensors (or flexors) of different animals, suggests that spinal circuits generating locomotion may indeed exert a stereotypic control over interneurons in specific cutaneous reflex pathways to motoneurons. The results are primarily discussed in Correspondence to: S. Rossignol
terms of the existing evidence for short-latency excitatory cutaneous reflexes in extensors in a variety of locomotive and non-locomotive preparations.
Key words: Cutaneous reflexes
Fictive locomotion Electroneurography - Semi-chronic spinal cat
Introduction Excitatory reflexes to flexors or extensors, evoked by stimulation of low-threshold cutaneous afferents, have been shown to undergo modulation during different phases of the locomotor step cycle. Such modulation has been seen in intact cats (Duysens and Stein 1978; Forssberg 1979; Duysens and Loeb 1980; Abraham et al. 1985; Drew and Rossignol 1987) and decerebrate animals (Duysens and Pearson 1976). The demonstration of such phase dependency in both walking spinal cats (Forssberg et al. 1975, 1977) and acute (Andersson et al. 1978; Schomburg and Behrends 1978; Schmidt et al. 1988, 1989) or chronic (Andersson et al. 1978) spinal cats during fictive locomotion strongly suggests that, in addition to certain inhibitory spinal interneurons (see Pratt and Jordan 1987), excitatory interneurons in segmental reflex pathways may be phasically driven by the spinal central pattern generator for locomotion. Evidence for such phasic control over excitatory cutaneous reflex pathways, however, may be strongest for pathways to flexor motoneurons. For example, with spinal cats walking on a treadmill, the most c o m m o n observation has been excitatory responses in flexors if the stimulus is applied during swing, but a mix o f excitatory and inhibitory responses in extensors if the stimulus is applied during stance (for review see Rossignol et al. 1988). Studies that have recorded directly from motoneurons during fictive locomotion have reported similar results. One investigation reported evidence for phase-dependent cutaneous-evoked excitatory postsynaptic potentials (EPSPs) in both flexor and extensor motoneurons but
237 f o u n d t h a t the m o d u l a t i o n in e x t e n s o r s was less pronounced and that patterns of modulation "varied s u b s t a n t i a l l y b e t w e e n different cells o f the s a m e species" ( A n d e r s s o n et al. 1978). T w o o t h e r studies r e p o r t e d clear evidence p r i m a r i l y for flexor m o t o n e u r o n s , w i t h m o r e v a r i a b l e results ( S c h o m b u r g a n d B e h r e n d s 1978) o r little evidence ( S c h m i d t et al. 1989) for p h a s e d e p e n d e n c y in extensor motoneurons. A more recent study (Mosc h o v a k i s et al. 1991) has s h o w n t h a t t w o s h o r t - l a t e n c y c u t a n e o u s p a t h w a y s giving e x c i t a t i o n to flexor d i g i t o r u m l o n g u s ( F D L ) m o t o n e u r o n s were c o n t r o l l e d differentially in the o p p o s i t e p h a s e o f the fictive l o c o m o t o r cycle. T h e superficial p e r o n e a l (SP) nerve gave e x c i t a t i o n to F D L d u r i n g flexion w h e n it was n o r m a l l y active, while the m e d i a l p l a n t a r nerve excited F D L m o t o n e u r o n s o n l y w h e n it also d i s c h a r g e d d u r i n g the e x t e n s o r phase. T h e a p p a r e n t i n c o n s i s t e n c i e s in r e s p o n s e s o f e x t e n s o r s to c u t a n e o u s s t i m u l a t i o n d u r i n g l o c o m o t i o n is puzzling, since c u t a n e o u s p r o j e c t i o n s to e x t e n s o r m o t o n e u r o n s h a v e l o n g b e e n d e s c r i b e d ( W i l s o n 1963; C o l e b a t c h a n d Gillies 1979). T w o r e c e n t i n t r a c e l l u l a r studies using n o n l o c o m o t i n g p r e p a r a t i o n s s u p p o r t the e a r l y suggestion o f H a g b a r t h (1952) t h a t h i n d l i m b e x t e n s o r m o t o r nuclei are p r e f e r e n t i a l l y excited b y c u t a n e o u s nerves a r i s i n g f r o m m o r e c i r c u m s c r i b e d s k i n regions t h a n is the case for flexor m o t o n e u r o n p o o l s . F o r e x a m p l e , in the first o f these studies, triceps s u r a e m o t o r nuclei - d e s p i t e b e i n g close f u n c t i o n a l synergists - were s h o w n to receive differential e x c i t a t o r y i n p u t f r o m each o f the two c u t a n e o u s sural nerves ( L a B e l l a et al. 1989). I n the s e c o n d s t u d y , in w h i c h five h i n d l i m b c u t a n e o u s nerves were tested, m e d i a l g a s t r o c n e m i u s m o t o n e u r o n s were s h o w n to receive p o t e n t a n d c o n v e r g e n t e x c i t a t o r y i n p u t f r o m t w o nerves w i t h n e a r b y o r o v e r l a p p i n g receptive fields (the c a u d a l c u t a n e o u s sural ( C C S ) a n d c a u d a l c u t a n e o u s f e m o r a l ( C C F ) n e r v e s ; L a B e l l a a n d M c C r e a 1990). T h e q u e s t i o n p r e s e n t l y a d d r e s s e d is w h e t h e r o r n o t a clear (i.e. consistent) p h a s e d e p e n d e n c y o f e x c i t a t o r y c u t a n e o u s reflexes in e x t e n s o r s d u r i n g fictive l o c o m o t i o n will e m e r g e if we focus o u r s t u d y o n triceps s u r a e a n d s t i m u l a t e c u t a n e o u s nerves w h i c h are k n o w n to p r o d u c e l o w - t h r e s h o l d excitation in triceps s u r a e m o t o n e u r o n s (see L a B e l l a et al. 1989 a n d L a B e l l a a n d M c C r e a 1990). A s this r e p o r t describes, in a d d i t i o n to e x c i t a t o r y c u t a n e o u s reflexes r e c o r d e d in h i n d l i m b flexor nerves o f spinal cats (1 3 w e e k s p o s t t r a n s e c t i o n ) , t h o s e e v o k e d in the a n k l e e x t e n s o r nerves also u n d e r g o c o n s i s t e n t p h a s e d e p e n d e n t m o d u l a t i o n d u r i n g the fictive step cycle. F u r t h e r m o r e , w i t h o n l y s o m e exceptions, these reflexes are e n h a n c e d d u r i n g the p h a s e o f the cycle in w h i c h the nerves a r e t y p i c a l l y active ( A n d e r s s o n et al. 1978; S c h o m b u r g a n d B e h r e n d s 1978), a l t h o u g h the p e r i o d o f i n c r e a s e d reflex r e s p o n s i v e n e s s does n o t strictly last t h r o u g h o u t the p e r i o d o f l o c o m o t o r activity. Materials and methods The aim of the experiments was to characterize short-latency responses to cutaneous nerve stimulation during fictive locomotion in the spinal cat. Normally, the adequate subject for such studies would be the acute spinal cat injected with nialamide and L-dopa
(Grillner and Zangger 1979; Schmidt et al. 1989). We have recently shown, in cats spinalized 1-2 weeks prior to the acute experiment, that fictive locomotion was sometimes evoked without drugs and also that, with clonidine only or L-dopa, locomotion was altogether easier to evoke and had a fi'equency more similar to the normal than in acutely spinalized cats (Pearson and Rossignol 1991). We have also shown that, as a function of time after spinalization, the fictive locomotor pattern becomes progressively more complex and expresses more features characteristic of the normal locomotor pattern. These facts led us to use animals (n = 11 ; mean weight 3.2 kg) that had been spinalized 1-3 weeks prior to the acute experiments.
Spinalization procedure Spinal cords were transected using sterile techniques and with the animals under pentobarbital sodium anaesthesia (32 mg/kg intraperitoneally or intravenously). Rostral and caudal cord segments were completely separated by dissection with fine forceps under a dissecting microscope. Penicillin G was administered during the first postoperative week (100000 IU/day). Bladders were manually expressed daily. Although the animals were not exercised on a treadmill during the postspinalization period, they were free to move around in individual large cages covered with absorbent cardboard, which was changed regularly. Cats were examined daily, and all cats had recovered brisk hindlimb reflexes when pressing on the foot or air stepping at the time of the acute experiment.
Preparation for the acute experiment Animals were surgically prepared under steroid anaesthesia, using intravenous Saffan 12 mg/kg (alphaxalone 9 mg/kg and alpha* dolone acetate 3 mg/kg). A tracheotomy was performed and one carotid artery cannulated to monitor blood pressure. An intravenous cannula was placed in either a forelimb or jugular vein for drug and fluid administration as well as for slow infusion of a glucose/ bicarbonate buffer. Atropine (0.12 mg) was given subcutaneously, prednisolone sodium succinate (20 mg every few hours) intramuscularly. Animals were then anaemically decerebrated by ligating the remaining intact carotid artery and the basilar artery (rostral to the posterior inferior cerebellar artery), which was reached by opening the skull ventrally at the level of the tympanic bulla (Pollock and Davis 1923). This was usually followed by a marked rigidity of the forelimbs and in a few cases the animal had to be ventilated. Given the residual effects of the anaesthetics, there was usually some time to initiate the dissection of hindlimb nerves before paralysis [pancuronium bromide (Pavuton) 0.3 mg/kg] and automatic ventilation. Previous experiments using Saffan for minor surgery in otherwise intact cats showed that cats were wide awake and walking around about 3 h after a single dose. In the present experiments, recordings started more than 3 h after injection of Saffan. Several nerves of the left (ipsilateral) hindlimb were cut and dissected free of surrounding tissue for subsequent stimulation (cutaneous nerves) or recording (motor nerves) on bipolar hook electrodes or cuff electrodes made of polysyloxane polymer and used in a monopolar configuration (Julien and Rossignol 1982; Pearson and Rossignol 1991). Semitendinosus (St), medial gastrocnemius (MG) and lateral gastrocnemius-soleus (LGS) nerves were placed in cuff electrodes. In some experiments the soleus (Sol) branch of the LGS nerve was dissected away to allow independent recording from lateral gastrocnemius (LG) and Sol efferents (in cuff electrodes or on bipolar hooks). In some experiments the contralateral St (coSt) nerve was also recorded through a monopotar cuff electrode. Cutaneous nerves stimulated for the production of reflex effects in ipsitateral motor nerves include the CCS and lateral cutaneous sural (LCS) nerves; the long distal branch of the CCF nerve; the saphenous nerve (Saph), taken approximately 1 cm above the level of the knee; and the SP nerve dissected at the ankle. CCS, LCS and CCF were stimulated on bipolar hook electrodes; Saph and SP were stimulated through monopolar cuff electrodes.
238
A
I
I
F
I
~b= 0.06 N=39
_ ~ 1 4 6 7 / _ 8 2 _ I
!qb-=. 0.14 . . .N=18 ....... qb = 024 N=24
,
297- 114 =
n
266-106=1601
'sa T
23 qf_=~_= 0.36 N_~_=_1
B
STIMULI t 6ms~ /k, ~15rns , I/\ 1
= 0.06
i/
. . . . . . . . . . . .
C
t_
I. . . . . . i I
N = 39 do = 0.06 INT = , 3 2 8 U
\
n
[-~
~
/
_
-
_110--_172=i
T /
t
.L . . . . . . I I
k
u 41nmJ
t I
= 0.64 N=10
,
147- 79 = 68 1"
qb = 0.75 N=19
~
4 0 - 3 0 = 10 $
qb = 0.85 N=15
,
0-0=0 I
_4,
T
Ii !
qb = 0,97 N=9
,
92-67=25
D
N=1o2
CONTROLS
I
T
G
qb = 0.06 , INT = 146 U ,
1"
I
I
5 ms MG
I
ii 14i!i1--~
070690
100 LU (,9 Z
O (3-
SUBTRACTED
E ,
STIM CCS
RECORDS
6O
m
/~
I
~c50 x
