Acta anat.
104: 340-348 (1979)
Interneuronal synapses in the local ganglia of the cat urinary bladder Erzsebet Feher and J. Vajda First Department of Anatomy, Semmelweis University Medical School, Budapest, Hungary
Key words. Urinary bladder • Cat • Autonomic nervous system
Introduction According to the classical concept, the urinary bladder is innervated by both parasympathetic and sympathetic nerves and constitutes an example of an tagonism between the two divisions of the autonomic nervous system [Elliott, 1907; Kuntz and Saecommmo, 1944; Gjone. 1965; Hamherger and Norberg, 1965], The efferent parasympathetic nerve fibres running the pelvic nerves establish synapses with postganglionic
neurons in the bladder wall [Carpenter and Root, 1951], It is also generally accepted that stimulation of the parasympathetic pelvic nerves produces contrac tion of the detrusor muscle [Carpenter and Rubin, 1967], Sympathetic inhibition of intramural para sympathetic ganglia was suggested since adrenergic nerve terminals forming synaptic structures around non-adrenergic cells have been demonstrated histochcmically in the bladder wall [Hamberger and Nor berg, 1965], The pattern of dual sympathetic and para
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Abstract. Theinterneuronal synapses of the urinary bladder in the cat were studied by electron microscopy. The great majority of the fibres containing vesicles are found within the ganglia occurring in the trigonum area. Morphologically differentiated synaptic contacts could be observed on the surface of the local neurons and between the different nerve processes. The presynaptic terminals can be divided into three types based on a combination of synaptic vesicles. Type I terminals, presumably cholinergic synaptic terminals, contain only small clear vesicles of 40-50 nm in diameter. Type 11 terminals, presumably adrenergic terminals, are characterized by small granulated vesicles of 40-60 nm in diameter. Type III terminals, probably of local origin, contain a variable number of large granulated vesicles of 80-140 nm in diameter. Occasionally, a.single nerve fibre contacted several (twoorfour) other nerve processes forming a typical synapse. In other cases, on one nerve cell soma or on other nerve processes there are two or three dilferenttype nerve terminals establishing synapses, ft might be inferred from these observations that convergence and divergence can occur in the local ganglia and that cholinergic and adrenergic synaptic terminals can modulate the ganglionic activity. However, a local circuit also can play an important role in coordinating the function of the bladder.
Inlerneuronal synapses in ihe local ganglia of ihe cat urinary bladder
341
lation established synapses on nerve cell bodies and processes. However, it was impossible to make any distinction between the profiles of dendrites and axons. The features of the synapses between the nerve fibres and nerve cell soma are, in prin ciple. similar to those of synapses described in other mammalian ganglia. The contacts were characterized by symmetrical membrane thickenings having a length of about 80-200 nm and being separated by a space of about 6-8 nm. which contains some lightly stained material. Synaptic vesicles are usually accumu lated in the axoplasm of nerve fibres. Their number and size varies considerably from one fibre to another. In analysing the synaptic re gions on the nerve soma and processes it was revealed that there are often several synaptic sites on each process. The number of the synapses on the surface of the cell somata was similar to that between the different nerve processes. Materials and methods According to the existence and the size of Adult cats of both sexes were anaesthetized w'ith granulated and clear(agranulated) vesicles, the pentobarbital and perfused with Karnovsky's fixative fibres can be generally classified into three [Kamovsky, 1965]. Tissue samples for electron micros groups. copy were obtained from the frontal part, the top, the Type I: The synaptic terminals contain ex sides and the trigonum of the bladder. Small pieces were excised and post-fixed in 1% osmic acid for 2 It clusively small clear vesicles of 40-50 nm in and embedded into Epon. Ultrathin sections were diameter (fig. I, 2), approximately the same stained with uranyl acetate and lead citrate. Electron size as those present in the cholinergic ter micrographs were taken with a Tesla BS 500 electron minals. microscope. Type II: The synaptic terminals contain numerous small granulated (dense-cored) ves icles of 40-60 nm in diameter, characteristic of Results adrenergic axonal varicosities (fig.3, 4). Be Several ganglia are mainly found at the sides of the granular vesicles a few clear and a level of the trigonum near the ureterovesical small number of scattered large granulated junction. The large majority of the nerve fibres vesicles also occur within these fibres. Type III: These synaptic terminals contain occurs within the ganglia containing either microtubules, mitochondria and neurofila a variable number of large granulated vesicles ments or swellings with a large number of vesi in addition to the small agranulated vesicles. cles. Nerve processes with such a vesicle popu The size of the granulated vesicles ranges be-
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sympathetic innervation of the bladder base has been confirmed by Dixon anti Gosling [1974]. Wakade and Kirpekar [1972] observed that the urinary bladder receives its sympathetic innervation via short post ganglionic nerve fibres from both right and left hypo gastric plexuses. However, Elmer [1975] found no an tagonism between the pelvic and hypogastric nerves in the rat bladder. The responses to stimulation of the pel vic and hypogastric nerves was bigger than the sum of the different responses. Elbadawi and Schenk [ 1968] and Schniman et al. [1972] observed that the vesical ganglia are composed of variable proportions of parasympa thetic (cholinergic) and sympathetic (adrenergic) cells, but the role and the nature of the postganglionic neu rons in the urinary bladder has remained unsolved. The aim of the present study is to demonstrate the principal structural relationship between the pre- and postganglionic neurons as well as between the different local nerve cells in the electron microscopical study of the local ganglia in the urinary bladder wall of the cat; furthermore, to clarify whether sympathetic (adren ergic) nerves are distributed only to blood vessels or innervate the vesical ganglionic cells as well.
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342 Fehér/ Vajda
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Interneurona! synapses in the local ganglia of the cat urinary bladder 343
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344 Fchér/Vajda
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Interneuronal synapses in the local ganglia of the cat urinary bladder 345
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For figures 1-8, see pages 342-345. Signs indicate I //in in all cases. Fig. 1. Synaptic terminals containing small clear vesicles of 30-50 nm in diameter. Arrows show the membrane thickenings between the nerve processes. Fig.2. Synaptic terminal on the surface of the type I nerve cell. The arrow points to the more prom inent postsynaptic thickening. Fig.3. Type II nerve terminals synapsing with another, probably local nerve process. Arrows point to the granulated vesicles of 40-60 nm in diameter. Fig.4. The nerve terminal containing small gran ulated vesicular synapses on the surface of the nerve cell body. The arrow points to the synaptic sites. Fig.5. Type III synaptic nerve terminal containing a large number of granulated vesicles of 80-140 nm in diameter (indicated by arrows), synapsing with an other probably local nerve process. Fig. 6. Nerve terminals with large granulated ves icles that establish synapses on the surface of a local nerve cell. Arrow point to the pre- and postsynaptic membrane thickenings. Fig. 7. Synapses between the different nerve proc esses. The arrow points to the desmosome-like mem brane thickenings without vesicular accumulation. Fig. 8. There are more synaptic sites (arrows) on the one nerve terminal.
One or more synaptic contacts established from the different types of nerve fibres may occur on the surface of the same nerve cells or on the other types of nerve fibres. Occasion ally, these nerve fibres can synapse in turn on the other processes of the neuron.
Discussion The junction in the urinary bladder ganglia is a remarkable subject both histologically and physiologically. It can be concluded from these results that several types of nerve terminals influencing the local nerve cells exist and most probably belong to different systems. The fine structures of the local ganglion cells and fibres in the urinary bladder have previously been described by Feher et at. [1978]. The presence of the different pre-ganglionic elements in contacts with the soma of type 1cells led us to suppose that the intramural neurons of the bladder are influenced by adrenergic (presumed sympathetic) and cho linergic (presumed parasympathetic) efferents and by the other local nerve cell processes as well. According to Uchizono [1975], at least two synaptic types are observed in the autonomic nerves. In one type acetylcholine, in the other type catecholamine is the transmitter. How ever, in the taenia coli two more types of synapses are observed, one of which belongs to so-called purinergic nerve synapses (P-type). It is now generally accepted that autonomic nerve profiles which contain predominantly small granulated vesicles (40-60 nm in diam eter) are associated with noradrenaline storage [Taxi and Droz, 1966: Burnslock and Robinson. 1967: Tranzer and Thoenen, 1967; Hokfell, 1968: Geffen and Liven, 1971]. The majority of adrenergic fibres establishes direct contact
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tween 80 and 140 nm (fig. 5, 6). This type shows the highest frequency of occurrence found throughout the ganglia. Occasionally, the thickenings of pre- and postsynaptic membranes are asymmetric, the postsynaptic thickening being more promi nent. Symmetrical thickenings of apposed membranes, without associated aggregations of vesicles, frequently occur between the dif ferent nerve fibres (fig. 7). Often more than one specialized contact zone can be observed be tween the adjacent nerve fibres. In addition, a few synaptic vesicles are close to the contact areas in both processes (fig. 8). On the cyto plasmic side of the presumed presynaptic membrane, clusters of vesicles lie close to the membrane in these cases, too.
Interneuronal synapses in the local ganglia of the cat urinary bladder
fibres and only very rarely axo-somatic syn apsis could be found. In the ganglia of the urinary bladder, the number of synapses be tween the different nerve fibres was similar to that found on the cell somata. The numerous synapses of the different nerve fibres on the same cells and fibres indicate a convergence of different pathways. In other cases a single nerve fibre contacted several (two or four) nerve processes forming typical synapses. It might be inferred from these ob servations that divergence can also occur in the local ganglia.
References Ambach, N. and Zar, M.: Non-cholinergic transmis sion by postganglionic motor neurones in the mammalian bladder. J. Physiol., Lond. 210: 761 783 (1970). Burnstock, G. and Robinson. P. M.: Localization of catecholamines and acetylcholinesterase in auton omic nerves. Circulation Res. 20-21: suppl.lll, pp. 43-51 (1967). Carpenter. F.G. and Root, W.S.: Effect of para sympathetic denervation on the feline bladder function. Am. J. Physiol. 166: 686-691 (1951). Carpenter, F.G. and Rubin. R.M.: The motor inner vation of the rat urinary bladder. J. Physiol., Lond. 192: 609-617 (1967). Dixon, J.S. and Gosling, J.A.: The distribution of noradrenergic nerves and small intensely fluores cent (SIF) cells in the cat urinary bladder. A light and electron microscope study. Cell. Tiss. Res. 150: 147-159 (1974). Elbadawi, A. and Schenk, E.A.: A new theory of the innervation of bladder musculature. I. Morphol ogy of the intrinsic vesical innervation apparatus. J. Urol. 99: 585-586(1968). Elbadawi, A. and Schenk, E.A.: A new theory of the innervation of bladder musculature. 4. Innervation of the vesicourethral sphincter. J. Urol. I ll: 613 615 (1974). Elliott, T. R.: The innervation of the bladder and urethra. J. Physiol., Lond. 35: 367-368 (1907).
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with perikarya of intramural neurons or their processes and may contact a cell body at sev eral points forming typical «en passage» syn apses. These fibres might affect the activity of the urinary bladder through these contacts by means of an inhibitory mechanism [Paion and Vizi, 1969; Vizi, 1968. 1974], Elbadawi and Schenk [1968] have proposed both direct and indirect control of the detrusor by adrenergic sympathetic fibres. The sympathetic and parasympathetic post ganglionic synapses provide a morphological basis for the modulating influence of the local ganglia in the urinary bladder. According to Gyermek [1962] and Vanov [1965], the vesical ganglia of the dog and rat appear to possess specific receptors for 5-hydroxytryptamine. Ambach and Zar [1970] pro posed that most of the postganglionic neurons in the bladder are of non-cholinergic nature. The third type of nerve fibres might correspond to those which contain non-cholinergic and non-adrenergic transmitters. Their structure is similar to that of the fibres observed in the isolated cat small intestine containing 5-hydroxytryptamine [Feher, 1977; Feber and Csanyi, 1978]. The third type of nerve fibres is presumed to be of local origin. They form synapses on the surfaces of the nerve cells and, with other nerve processes, provide the first morphological evidence for an interaction of the different, probably local components peripherically in the bladder wall. The patches of desmosome-like contacts and the absence of vesicular accumulation in these areas points to the possibility of electro tonic effects through these contacts without transmitter. In the sympathetic chain ganglia. Szentdgolhai [1964] observed that the far majority of true synaptic contacts were between the den drites and terminal branches of preganglionic
347
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new concept based on a histochemical study. Br. J. Urol. 44: 698-712(1972). Szentâgothai, J.: The structure of autonomic interneural synapse. Acta neuroveg. 26: 338-358 (1964). Taxi, J. et Droz. B.: Etude de l’incorporation de nor adrenaline-3H (Na-:,H ) et de 5-hydroxytryptophane-3H (5-HTP-3H) dans les fibres nerveuses du canal déférent et de l'intestin. C.r. hebd. Séanc. Acad. Sei., Paris 263: 1237-1240 ( 1966). Tranzer, J.P. und Thoenen, H.: Ultramorphologische Veränderungen der sympathischen Nervenendi gungen der Katze nach Vorbehandlung mit 5- und 6-Hydroxy-Dopamine. Arch. Pharmakol. exp. Pa thol. 257: 343-344 (1967). Uchizono, K.: Excitation and inhibition. Synapticmorphology (Igaku Shoin/Elsevier, Tokyo/Amsterdam 1975). Vanov, S. : Responses of the rat urinary bladder in situ to drugs and to nerve stimulation. Br. J. Pharma col. 24: 591-600(1965). Vizi, E.S.: The inhibitory action of noradrenaline on release of acetylcholine from guinea-pig ileum lon gitudinal strips. Arch. Pharmakol. 259: exp. Pa thol. 199 200 (1968). Vizi, E.S. : Interaction between adrenergic and cholin ergic systems: presynaptic inhibitory effect of nor adrenaline on acetylcholine release. J. neural transm., suppl. XI, pp.61-78 (1974). Wakade, A.R. and Kirpekar. S. M.: Sympathetic in nervation of urinary bladder of the guinea-pig. Am. J. Physiol. 223: 1477-1480(1972).
Received: December 2, 1978 F.rzsebct Feher, First Department of Anatomy. Semmelweis University Medical School. Budapest 1450 (Hungary)
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Elmer, M.: Autonomic innervation of the rat urinary bladder; thesis Lund (1975). Feher, E.: Effect of 5,6-dihydroxytryptamine on the structure of nerve fibres in the chronically isolated cat ileum. Acta anat. 98: 83-91 (1977). Feher, E. and Csanyi, K.: Ultrastructural effects of parachlorophenylalanine, 5-hydroxytryptamine and the imiprantine group on the nerve processes of the small intestine. Acta anat. 100: 61 -67 (1978). Feher, E.; Csdnyi, K., and Vajda, J.: Ultrastructure of the nerve cells and fibres in the urinary bladder wall of the cat. Acta anat. 103: 109-118 (1978). Geffen, L.B. and Livett, B.G.: Synaptic vesicles in sympathetic neurons. Physiol. Rev. 51: 98-157 (1971). Gjone. R.: A dual peripheral and supraspinal auton omic influence on the urinary bladder(Universitetsforlaget, Oslo 1965). Gyermck, L.: Action of 5-hydroxytryptamine on the urinary bladder of the dog. Archs int. Pharntacodyn. Ther. 137: 137-144 (1962). Hamberger, B. and Norberg, K.A.: Adrenergic syn aptic terminals and nerve cells in bladder ganglia of the cat. Int. J. Ncuropharmacol. 4 :41-45 (1965). Hokfelt, T .: In vitro studies on central and peripheral monoamine neurones at the ultrastructural level. Z. Zellforsch. 91: 1-74 (1968). Karnovsky, M.J.: A formaldchyde-glutaraldehyde fix ative of high osmolarity for use in electromicros copy. J. Cell Biol. 27: 137-138 (1965). Kuntz, A. and Saccomanno, G.: Sympathetic inner vation of the detrusor muscle. J. Urol. 51: 535-536 (1944). Paton, W.d. M. and Vizi, E.S.: The inhibition action of noradrenaline and adrenaline on acetylcholine output by guinea-pig ileum longitudinal muscle strip. Br. J. Pharm. 35: 10-28 (1969). Schulman, C. C.; Duarte; Escalante, O., and Boyarsky, S.: The ureterovesical innervation. A
104: 340-348 (1979)
Interneuronal synapses in the local ganglia of the cat urinary bladder Erzsebet Feher and J. Vajda First Department of Anatomy, Semmelweis University Medical School, Budapest, Hungary
Key words. Urinary bladder • Cat • Autonomic nervous system
Introduction According to the classical concept, the urinary bladder is innervated by both parasympathetic and sympathetic nerves and constitutes an example of an tagonism between the two divisions of the autonomic nervous system [Elliott, 1907; Kuntz and Saecommmo, 1944; Gjone. 1965; Hamherger and Norberg, 1965], The efferent parasympathetic nerve fibres running the pelvic nerves establish synapses with postganglionic
neurons in the bladder wall [Carpenter and Root, 1951], It is also generally accepted that stimulation of the parasympathetic pelvic nerves produces contrac tion of the detrusor muscle [Carpenter and Rubin, 1967], Sympathetic inhibition of intramural para sympathetic ganglia was suggested since adrenergic nerve terminals forming synaptic structures around non-adrenergic cells have been demonstrated histochcmically in the bladder wall [Hamberger and Nor berg, 1965], The pattern of dual sympathetic and para
Downloaded by: Karolinska Institutet, University Library 130.237.122.245 - 1/24/2019 4:08:52 AM
Abstract. Theinterneuronal synapses of the urinary bladder in the cat were studied by electron microscopy. The great majority of the fibres containing vesicles are found within the ganglia occurring in the trigonum area. Morphologically differentiated synaptic contacts could be observed on the surface of the local neurons and between the different nerve processes. The presynaptic terminals can be divided into three types based on a combination of synaptic vesicles. Type I terminals, presumably cholinergic synaptic terminals, contain only small clear vesicles of 40-50 nm in diameter. Type 11 terminals, presumably adrenergic terminals, are characterized by small granulated vesicles of 40-60 nm in diameter. Type III terminals, probably of local origin, contain a variable number of large granulated vesicles of 80-140 nm in diameter. Occasionally, a.single nerve fibre contacted several (twoorfour) other nerve processes forming a typical synapse. In other cases, on one nerve cell soma or on other nerve processes there are two or three dilferenttype nerve terminals establishing synapses, ft might be inferred from these observations that convergence and divergence can occur in the local ganglia and that cholinergic and adrenergic synaptic terminals can modulate the ganglionic activity. However, a local circuit also can play an important role in coordinating the function of the bladder.
Inlerneuronal synapses in ihe local ganglia of ihe cat urinary bladder
341
lation established synapses on nerve cell bodies and processes. However, it was impossible to make any distinction between the profiles of dendrites and axons. The features of the synapses between the nerve fibres and nerve cell soma are, in prin ciple. similar to those of synapses described in other mammalian ganglia. The contacts were characterized by symmetrical membrane thickenings having a length of about 80-200 nm and being separated by a space of about 6-8 nm. which contains some lightly stained material. Synaptic vesicles are usually accumu lated in the axoplasm of nerve fibres. Their number and size varies considerably from one fibre to another. In analysing the synaptic re gions on the nerve soma and processes it was revealed that there are often several synaptic sites on each process. The number of the synapses on the surface of the cell somata was similar to that between the different nerve processes. Materials and methods According to the existence and the size of Adult cats of both sexes were anaesthetized w'ith granulated and clear(agranulated) vesicles, the pentobarbital and perfused with Karnovsky's fixative fibres can be generally classified into three [Kamovsky, 1965]. Tissue samples for electron micros groups. copy were obtained from the frontal part, the top, the Type I: The synaptic terminals contain ex sides and the trigonum of the bladder. Small pieces were excised and post-fixed in 1% osmic acid for 2 It clusively small clear vesicles of 40-50 nm in and embedded into Epon. Ultrathin sections were diameter (fig. I, 2), approximately the same stained with uranyl acetate and lead citrate. Electron size as those present in the cholinergic ter micrographs were taken with a Tesla BS 500 electron minals. microscope. Type II: The synaptic terminals contain numerous small granulated (dense-cored) ves icles of 40-60 nm in diameter, characteristic of Results adrenergic axonal varicosities (fig.3, 4). Be Several ganglia are mainly found at the sides of the granular vesicles a few clear and a level of the trigonum near the ureterovesical small number of scattered large granulated junction. The large majority of the nerve fibres vesicles also occur within these fibres. Type III: These synaptic terminals contain occurs within the ganglia containing either microtubules, mitochondria and neurofila a variable number of large granulated vesicles ments or swellings with a large number of vesi in addition to the small agranulated vesicles. cles. Nerve processes with such a vesicle popu The size of the granulated vesicles ranges be-
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sympathetic innervation of the bladder base has been confirmed by Dixon anti Gosling [1974]. Wakade and Kirpekar [1972] observed that the urinary bladder receives its sympathetic innervation via short post ganglionic nerve fibres from both right and left hypo gastric plexuses. However, Elmer [1975] found no an tagonism between the pelvic and hypogastric nerves in the rat bladder. The responses to stimulation of the pel vic and hypogastric nerves was bigger than the sum of the different responses. Elbadawi and Schenk [ 1968] and Schniman et al. [1972] observed that the vesical ganglia are composed of variable proportions of parasympa thetic (cholinergic) and sympathetic (adrenergic) cells, but the role and the nature of the postganglionic neu rons in the urinary bladder has remained unsolved. The aim of the present study is to demonstrate the principal structural relationship between the pre- and postganglionic neurons as well as between the different local nerve cells in the electron microscopical study of the local ganglia in the urinary bladder wall of the cat; furthermore, to clarify whether sympathetic (adren ergic) nerves are distributed only to blood vessels or innervate the vesical ganglionic cells as well.
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342 Fehér/ Vajda
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Interneurona! synapses in the local ganglia of the cat urinary bladder 343
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344 Fchér/Vajda
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Interneuronal synapses in the local ganglia of the cat urinary bladder 345
Fehcr'Vajda
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For figures 1-8, see pages 342-345. Signs indicate I //in in all cases. Fig. 1. Synaptic terminals containing small clear vesicles of 30-50 nm in diameter. Arrows show the membrane thickenings between the nerve processes. Fig.2. Synaptic terminal on the surface of the type I nerve cell. The arrow points to the more prom inent postsynaptic thickening. Fig.3. Type II nerve terminals synapsing with another, probably local nerve process. Arrows point to the granulated vesicles of 40-60 nm in diameter. Fig.4. The nerve terminal containing small gran ulated vesicular synapses on the surface of the nerve cell body. The arrow points to the synaptic sites. Fig.5. Type III synaptic nerve terminal containing a large number of granulated vesicles of 80-140 nm in diameter (indicated by arrows), synapsing with an other probably local nerve process. Fig. 6. Nerve terminals with large granulated ves icles that establish synapses on the surface of a local nerve cell. Arrow point to the pre- and postsynaptic membrane thickenings. Fig. 7. Synapses between the different nerve proc esses. The arrow points to the desmosome-like mem brane thickenings without vesicular accumulation. Fig. 8. There are more synaptic sites (arrows) on the one nerve terminal.
One or more synaptic contacts established from the different types of nerve fibres may occur on the surface of the same nerve cells or on the other types of nerve fibres. Occasion ally, these nerve fibres can synapse in turn on the other processes of the neuron.
Discussion The junction in the urinary bladder ganglia is a remarkable subject both histologically and physiologically. It can be concluded from these results that several types of nerve terminals influencing the local nerve cells exist and most probably belong to different systems. The fine structures of the local ganglion cells and fibres in the urinary bladder have previously been described by Feher et at. [1978]. The presence of the different pre-ganglionic elements in contacts with the soma of type 1cells led us to suppose that the intramural neurons of the bladder are influenced by adrenergic (presumed sympathetic) and cho linergic (presumed parasympathetic) efferents and by the other local nerve cell processes as well. According to Uchizono [1975], at least two synaptic types are observed in the autonomic nerves. In one type acetylcholine, in the other type catecholamine is the transmitter. How ever, in the taenia coli two more types of synapses are observed, one of which belongs to so-called purinergic nerve synapses (P-type). It is now generally accepted that autonomic nerve profiles which contain predominantly small granulated vesicles (40-60 nm in diam eter) are associated with noradrenaline storage [Taxi and Droz, 1966: Burnslock and Robinson. 1967: Tranzer and Thoenen, 1967; Hokfell, 1968: Geffen and Liven, 1971]. The majority of adrenergic fibres establishes direct contact
Downloaded by: Karolinska Institutet, University Library 130.237.122.245 - 1/24/2019 4:08:52 AM
tween 80 and 140 nm (fig. 5, 6). This type shows the highest frequency of occurrence found throughout the ganglia. Occasionally, the thickenings of pre- and postsynaptic membranes are asymmetric, the postsynaptic thickening being more promi nent. Symmetrical thickenings of apposed membranes, without associated aggregations of vesicles, frequently occur between the dif ferent nerve fibres (fig. 7). Often more than one specialized contact zone can be observed be tween the adjacent nerve fibres. In addition, a few synaptic vesicles are close to the contact areas in both processes (fig. 8). On the cyto plasmic side of the presumed presynaptic membrane, clusters of vesicles lie close to the membrane in these cases, too.
Interneuronal synapses in the local ganglia of the cat urinary bladder
fibres and only very rarely axo-somatic syn apsis could be found. In the ganglia of the urinary bladder, the number of synapses be tween the different nerve fibres was similar to that found on the cell somata. The numerous synapses of the different nerve fibres on the same cells and fibres indicate a convergence of different pathways. In other cases a single nerve fibre contacted several (two or four) nerve processes forming typical synapses. It might be inferred from these ob servations that divergence can also occur in the local ganglia.
References Ambach, N. and Zar, M.: Non-cholinergic transmis sion by postganglionic motor neurones in the mammalian bladder. J. Physiol., Lond. 210: 761 783 (1970). Burnstock, G. and Robinson. P. M.: Localization of catecholamines and acetylcholinesterase in auton omic nerves. Circulation Res. 20-21: suppl.lll, pp. 43-51 (1967). Carpenter. F.G. and Root, W.S.: Effect of para sympathetic denervation on the feline bladder function. Am. J. Physiol. 166: 686-691 (1951). Carpenter, F.G. and Rubin. R.M.: The motor inner vation of the rat urinary bladder. J. Physiol., Lond. 192: 609-617 (1967). Dixon, J.S. and Gosling, J.A.: The distribution of noradrenergic nerves and small intensely fluores cent (SIF) cells in the cat urinary bladder. A light and electron microscope study. Cell. Tiss. Res. 150: 147-159 (1974). Elbadawi, A. and Schenk, E.A.: A new theory of the innervation of bladder musculature. I. Morphol ogy of the intrinsic vesical innervation apparatus. J. Urol. 99: 585-586(1968). Elbadawi, A. and Schenk, E.A.: A new theory of the innervation of bladder musculature. 4. Innervation of the vesicourethral sphincter. J. Urol. I ll: 613 615 (1974). Elliott, T. R.: The innervation of the bladder and urethra. J. Physiol., Lond. 35: 367-368 (1907).
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with perikarya of intramural neurons or their processes and may contact a cell body at sev eral points forming typical «en passage» syn apses. These fibres might affect the activity of the urinary bladder through these contacts by means of an inhibitory mechanism [Paion and Vizi, 1969; Vizi, 1968. 1974], Elbadawi and Schenk [1968] have proposed both direct and indirect control of the detrusor by adrenergic sympathetic fibres. The sympathetic and parasympathetic post ganglionic synapses provide a morphological basis for the modulating influence of the local ganglia in the urinary bladder. According to Gyermek [1962] and Vanov [1965], the vesical ganglia of the dog and rat appear to possess specific receptors for 5-hydroxytryptamine. Ambach and Zar [1970] pro posed that most of the postganglionic neurons in the bladder are of non-cholinergic nature. The third type of nerve fibres might correspond to those which contain non-cholinergic and non-adrenergic transmitters. Their structure is similar to that of the fibres observed in the isolated cat small intestine containing 5-hydroxytryptamine [Feher, 1977; Feber and Csanyi, 1978]. The third type of nerve fibres is presumed to be of local origin. They form synapses on the surfaces of the nerve cells and, with other nerve processes, provide the first morphological evidence for an interaction of the different, probably local components peripherically in the bladder wall. The patches of desmosome-like contacts and the absence of vesicular accumulation in these areas points to the possibility of electro tonic effects through these contacts without transmitter. In the sympathetic chain ganglia. Szentdgolhai [1964] observed that the far majority of true synaptic contacts were between the den drites and terminal branches of preganglionic
347
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Received: December 2, 1978 F.rzsebct Feher, First Department of Anatomy. Semmelweis University Medical School. Budapest 1450 (Hungary)
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