Origin of peptide-containing fibers in the inferior mesenteric ganglion of the guinea-pig: Immunohistochemical studies with antisera to substance P,enkephalin, vasoactive intestinal polypeptide,cholecystokinin and bombesin

After different denervation procedures the guinea-pig inferior mesenteric ganglion was analysed by immunohistochemistry using antisera to substance P, enkephalin, vasoactive intestinal polypeptide, cholecystokinin and bombesin. The results demonstrate that each of the nerve trunks connected to the ganglion carries specific peptidergic pathways. Thus, the lumbar splachnic nerves contain substance P-immunoreactive primary afferent neurons, which to a large extent traverse the ganglion, and enkephalin-immunoreactive preganglionic neurons; the colonie nerves carry vasoactive intestinal polypeptide-, cholecystokinin- and bombesin-immunoreactive fibers from the distal colon to the ganglion; the hypogastric nerves contain vasoactive intestinal polypeptide-positive fibers from the pelvic plexus; and the intermesenteric nerve contains vasoactive intestinal polypeptide, cholecystokinin, substance P and enkephalin from divergent sources. By studying accumulations of peptides in ligated lumbar splanchnic, intermesenteric, hypogastric and colonic nerves the existence of these major peptidergic pathways was confirmed and evidence was obtained for additional, not so prominent, peptidergic projections. The results are discussed in view of earlier morphological and physiological studies.     

Autonomic innervation of reproductive organs: analysis of the neurons whose axons project in the main penile nerve in the pelvic plexus of the rat

An understanding of the composition of the various nerves of the pelvic plexus is essential in the design of studies to explore the autonomic control of pelvic visceral tissues. As a correlate of this interest, the present study was designed to determine the composition of the main penile nerve in the pelvic plexus of the laboratory rat, an animal commonly used for studies of reproductive physiology. Retrograde tracing studies indicate that the main penile nerve contains neurons which project to the penile crura, the corpus spongiosum, and the bulbourethral glands. The main penile nerve is the major source of neurons which innervate the corpus spongiosum and bulbourethral gland and contains about one-third of all parasympathetic neurons which project to the penile crura. Dye placed on the proximal cut end of the main penile nerve indicates that neurons in the parasympathetic region of the spinal cord (L6-S1) and to a lesser extent a sympathetic region of the cord, L1-L2, provide preganglionic innervation to ganglion cells in the main pelvic nerve. Processes of neurons in dorsal root ganglia L6-S1 and of neurons in the abdominopelvic sympathetic chain course in the main penile nerve to unknown destinations. In many respects this presumed postganglionic fiber tract is essentially a region of the pelvic plexus which subserves extrapelvic visceral tissues.     

Transmitter profile and spinal inputs of pelvic ganglion cells projecting with preganglionic axons along the hypogastric and pelvic nerves of the male rat

Pelvic autonomic ganglion cells receive spinal preganglionic inputs via the hypogastric (lumbar) or pelvic (sacral) nerves. Damage to these nerves stimulates axogenesis (sprouting) from pelvic ganglion cells and two possible triggers are deafferentation (decentralisation) or, if some ganglion cells project centrally in these nerves, axotomy. We have used a combination of retrograde tracing and immunohistochemistry in male rats to identify the number of pelvic ganglion cells that project centrally along these nerves, their transmitter type and the spinal level of their preganglionic inputs. Only a small number (<1%) of pelvic ganglion cells project along these nerves; 29-65 project in each hypogastric nerve and 41-71 in each pelvic nerve. These neurons comprise of both cholinergic and noradrenergic classes and the majority receive preganglionic inputs from the nerve in which they also project. These results suggest that damage of the hypogastric and pelvic nerves close to the pelvic ganglion is unlikely to cause axotomy of many pelvic ganglion cells. Therefore deafferentation rather than axotomy is likely to be the primary trigger of axogenesis occurring in pelvic ganglia after these lesions.     

Preganglionic fibers in the rat hypogastric nerve project bilaterally to pelvic ganglia

Stimulation of the hypogastric nerve (HGN) often evokes bilateral responses in some pelvic organs. Retrograde labeling studies indicate that axons of postganglionic neurons often cross to the opposite side. However, there is little information available as to whether preganglionic fibers in the HGN have a contralateral projection to pelvic ganglia. A retrograde tracer was injected into the left major pelvic ganglion (MPG) in rats receiving various lesions of preganglionic nerves (HGN and pelvic nerve, PN). The lumbar spinal cord was then examined for location and number of dye-filled neurons. In a second approach, the incidence of synaptophysin immunoreactivity (SN-IR) perineuronal profiles (baskets) was examined in the MPG and in the accessory pelvic ganglia (APG) after nerve lesions. Labeled neuronal profiles were found in spinal cord nuclei (Lumbar_1–2) after dye injection of the MPG in animals with an intact contralateral HGN. Cutting both HGNs virtually eliminated dye labeling in the lumbar cord, as did severing commissural branches (CB) between pelvic ganglia (leaving the contralateral HGN intact). Some SN-IR baskets were found in the left APG when only the contralateral HGN was intact, but baskets were rare when all four preganglionic nerves were cut. It could not be determined whether the HGN projects to the contralateral MPG, since SN-IR baskets were numerous in the MPG even when all four nerves were cut. This study has shown that some preganglionic fibers in the HGN synapse on neurons in contralateral pelvic ganglia. Both the APG and MPG receive contralateral innervation, but it is likely that neurons in the APG are the primary target of this input. Thus, in addition to crossing postganglionic fibers, a portion of the bilateral control of pelvic tissues is accomplished by preganglionic fibers which target autonomic neurons in contralateral ganglia. Anat. Rec. 252:229–234, 1998. © 1998 Wiley-Liss, Inc.     

Substance P immunoreactivity in the major pelvic ganglion of the rat

Substance P immunoreactivity in the major pelvic ganglion (MPG) of the rat was studied to define a possible role for this neuropeptide in functions of the pelvic portion of the autonomic nervous system. Substance P immunoreactivity was found in three locations in the ganglion: 1) as a plexus of varicose fibers, 2) in small intensely fluorescent (SIF) cells, and 3) after colchicine pretreatment, in some principal neurons. The perineuronal plexus of fibers appeared as small varicosities closely related to the somae of principal neurons. Approximately 10-20% of principal neurons were enclosed by a substance P-positive plexus. SIF cells were intensely stained for substance P. The general relationships of SIF cells in this ganglion were confirmed by their staining for substance P: their occurrence singly or in large clusters, their short tapering processes often related to principal neurons, and the occasional presence of a beaded process. Colchicine treatment resulted in the appearance of rare principal neurons that stained for substance P. The pelvic nerve was surgically interrupted to determine whether the perineuronal plexus of varicose fibers had an intrinsic origin or arose from cell bodies outside the ganglion. The perineuronal plexus was virtually absent following this procedure. The results of this study indicate that principal neurons in the major pelvic ganglion may be subject to the influence of substance P derived from two sources: 1) intrinsic substance P-containing SIF cells and 2) neurons probably residing in dorsal root ganglia. The nature of principal neurons that acquire staining for substance P after colchicine is unclear.     

Target specific organization and neuron types of the dog pelvic ganglia: a retrograde-tracing and immunohistochemical study

The major pelvic ganglion in both the rat and guinea pig has been extensively studied because of its anatomical simplicity. To clarify the target specific neural pathway in the diffusely distributed pelvic ganglia of larger animals, the pelvic plexus of the female dog was investigated by retrograde tracing and immunohistochemistry. The whole mount staining of the pelvic plexus with acetylcholinesterase histochemistry revealed 70-100 ganglia of varying sizes. Neurons retrogradely labeled from the rectum were mainly found in ganglia located in the dorso-caudal part of the plexus. The majority of these were non-catecholaminergic, immunoreactive for either calbindin (Calb) or neuropeptide Y (NPY), and characteristically associated with baskets of enkephalin (ENK)-immunoreactive varicose fibers. Neurons projecting to the utero-vaginal walls were distributed in ganglia located in the ventro-caudal part of the plexus. These mainly consisted of two major neuron groups: catecholaminergic Calb-immunoreactive neurons, and non-catecholaminergic neurons containing nitric oxide synthase (NOS) and/or vasoactive intestinal peptide (VIP), which were preferentially associated with a network of ENK-immunoreactive varicose fibers. Neurons retrogradely labeled from the urinary bladder mainly occurred in ganglia located around the junction between the ureter and the bladder. These consisted of catecholaminergic Calb neurons and noncatecholaminergic neurons containing Calb or NOS. Only a few ENK-immunoreactive fibers were found within the clusters of catecholaminergic neurons. These results indicate that organ specific neurons are located in separate ganglia and have both a distinctive composition of neuron types as well as different innervation by preganglionic fibers.     

Extrinsic innervation of the pelvic organs in the lesser pelvis of human embryos

Realistic models to understand the developmental appearance of the pelvic nervous system in mammals are scarce. We visualized the development of the inferior hypogastric plexus and its preganglionic connections in human embryos at 4–8 weeks post-fertilization, using Amira 3D reconstruction and Cinema 4D-remodelling software. We defined the embryonic lesser pelvis as the pelvic area caudal to both umbilical arteries and containing the hindgut. Neural crest cells (NCCs) appeared dorsolateral to the median sacral artery near vertebra S1 at ~5 weeks and had extended to vertebra S5 1 day later. Once para-arterial, NCCs either formed sympathetic ganglia or continued to migrate ventrally to the pre-arterial region, where they formed large bilateral inferior hypogastric ganglionic cell clusters (IHGCs). Unlike more cranial pre-aortic plexuses, both IHGCs did not merge because the 'pelvic pouch', a temporary caudal extension of the peritoneal cavity, interposed. Although NCCs in the sacral area started to migrate later, they reached their pre-arterial position simultaneously with the NCCs in the thoracolumbar regions. Accordingly, the superior hypogastric nerve, a caudal extension of the lumbar splanchnic nerves along the superior rectal artery, contacted the IHGCs only 1 day later than the lumbar splanchnic nerves contacted the inferior mesenteric ganglion. The superior hypogastric nerve subsequently splits to become the superior hypogastric plexus. The IHGCs had two additional sources of preganglionic innervation, of which the pelvic splanchnic nerves arrived at ~6.5 weeks and the sacral splanchnic nerves only at ~8 weeks. After all preganglionic connections had formed, separate parts of the inferior hypogastric plexus formed at the bladder neck and distal hindgut.     

Remodelling of connections in pelvic ganglia after hypogastric nerve crush

Pelvic ganglia innervate the urogenital organs and contain both sympathetic and parasympathetic neurons. Previous studies have shown that within days of cutting either the lumbar or sacral preganglionic axons that innervate pelvic ganglia, many axon collaterals grow and appear to form specific connections with denervated pelvic neurons. Here we have examined the longer term consequences of partial deafferentation by studying pelvic ganglia up to 7 weeks after hypogastric nerve (HGN) crush, a lesion which also allows faster regeneration of spinal axons. Noradrenergic neurons were denervated by HGN crush, as demonstrated by loss of varicosities immunostained for the synaptic proteins, synaptophysin and synapsin. A week after HGN crush, axon collaterals grew from parasympathetic pelvic ganglion neurons, shown by the presence of numerous varicose fibers immunostained for vasoactive intestinal peptide (VIP). These VIP fibers were poorly stained or unstained for synaptophysin, even after 7 weeks. At early post-operative times the VIP fibers grew irregularly; however, with longer post-operative times they appeared to target particular VIP-negative, noradrenergic neurons. Our results also indicate that some lumbar preganglionic axons regenerated during the post-operative period, although this only affected a minority of sympathetic neurons. These reinnervated sympathetic neurons were not associated with VIP fibers, suggesting that the new intrinsic connections may have precluded regeneration or targeting of preganglionic axons. Together these results demonstrate that there is considerable remodelling within pelvic ganglia after partial deafferentation. This occurs under conditions where spinal preganglionic axons can regenerate. New intra-ganglionic connectivity may be permanent and may impact on this regeneration.     

Differential expression of calcium channels in sympathetic and parasympathetic preganglionic inputs to neurons in paracervical ganglia of guinea-pigs

Neurons in pelvic ganglia receive nicotinic excitatory post-synaptic potentials (EPSPs) from sacral preganglionic neurons via the pelvic nerve, lumbar preganglionic neurons via the hypogastric nerve or both. We tested the effect of a range of calcium channel antagonists on EPSPs evoked in paracervical ganglia of female guinea-pigs after pelvic or hypogastric nerve stimulation. omega-Conotoxin GVIA (CTX GVIA, 100 nM) or the novel N-type calcium channel antagonist, CTX CVID (100 nM) reduced the amplitude of EPSPs evoked after pelvic nerve stimulation by 50-75% but had no effect on EPSPs evoked by hypogastric nerve stimulation. Combined addition of CTX GVIA and CTX CVID was no more effective than either antagonist alone. EPSPs evoked by stimulating either nerve trunk were not inhibited by the P/Q calcium channel antagonist, omega-agatoxin IVA (100 nM), nor the L-type calcium channel antagonist, nifedipine (30 microM). SNX 482 (300 nM), an antagonist at some R-type calcium channels, inhibited EPSPs after hypogastric nerve stimulation by 20% but had little effect on EPSPs after pelvic nerve stimulation. Amiloride (100 microM) inhibited EPSPs after stimulation of either trunk by 40%, while nickel (100 microM) was ineffective. CTX GVIA or CTX CVID (100 nM) also slowed the rate of action potential repolarization and reduced afterhyperpolarization amplitude in paracervical neurons. Thus, release of transmitter from the terminals of sacral preganglionic neurons is largely dependent on calcium influx through N-type calcium channels, although an unknown calcium channel which is resistant to selective antagonists also contributes to release. Release of transmitter from lumbar preganglionic neurons does not require calcium entry through either conventional N-type calcium channels or the variant CTX CVID-sensitive N-type calcium channel and seems to be mediated largely by a novel calcium channel.     

Localization of vasoactive intestinal polypeptide in penile erectile tissue and in the major pelvic ganglion of the rat

Vasoactive intestinal polypeptide was localized by immunocytochemical techniques in the major pelvic ganglion and penile erectile tissue of the rat. Vasoactive intestinal polypeptide fibers were concentrated in penile crura with the density of innervation decreasing distally. The helicine arteries were very densely innervated while fewer fibers surrounded the deep artery of the penis. Intrinsic smooth muscle of the cavernous bodies received a moderate supply of vasoactive intestinal polypeptide immunoreactive fibers. Dorsal vascular structures, including the deep dorsal vein were innervated by vasoactive intestinal polypeptide fibers. Vasoactive intestinal polypeptide immunoreactive cell bodies were found in the major pelvic ganglion, concentrated on one end of the ganglion. Rectrograde studies with a dye injected into the penile crura indicated that neurons in major pelvic ganglion projected to the penis. Combined dye and immunofluorescent studies showed that all the dye-labeled neurons were immunoreactive for vasoactive intestinal polypeptide.

It is concluded that all vascular beds in the penis of the rat are innervated by vasoactive intestinal polypeptide fibers and that the extent of the innervation is related to the occurrence of smooth muscle. Neurons in the major pelvic ganglion probably are the main source of vasoactive intestinal polypeptide fibers to the penis.     

Termination pattern and fine structural characteristics of GABA- and [Met]enkephalin-containing nerve fibers and synapses in the superior cervical ganglion of adult rat.

Morphological features of nerve fibers and synapses containing GABA and [Met]enkephalin were studied at the light and electron microscopic levels in the superior cervical ganglia of rats by pre- and postembedding immunohistochemistry. Both GABA and [Met]enkephalin immunoreactivities were found in varicose nerve fibers, forming diffuse networks which were denser in the rostral than in the caudal part of each ganglion. For both antigens rich and basket-like innervation was observed around some of the principal neurons. The GABA-immunoreactive fibers were evenly stained, while in case of [Met]enkephalin-positive nerve fibers the varicosities showed intensive immunopositivity only. Postembedding immunochemistry revealed that both inhibitory substances were located in axon varicosities which established asymmetric synapses of Gray I type. Fine structural investigation revealed that GABA-like immunoreactivity was confined in the nerve endings to the clear synaptic vesicles of 40 nm diameter, whereas the immunogold particles, indicating the occurrence of [Met]enkephalin, were located over the large dense-cored vesicles of 120 nm diameter. The clear and dense-cored vesicles were, however, mixed in the nerve endings labeled by either neurotransmitter substance. Interestingly, the [Met]enkephalin-immunopositive axon terminals were found, consequently, in synaptic contacts with dendrites containing dense bodies in a row underlying the postsynaptic membrane thickening. Since nerve terminals with GABA-like immunoreactivity established synapses of Gray I type without such subjunctional bodies, one can reasonably assume that, in spite of similarities in termination pattern, there is no co-existence of GABA and enkephalin in the axons in the superior cervical ganglion.     

Organization of lumbar spinal outflow to distal colon and pelvic organs

The lumbar sympathetic outflow projects through the lumbar splanchnic, lumbar colonic, and hypogastric nerves (and to a lesser degree through the sacral sympathetic chain and pelvic nerves). It is thought to be involved in the regulation of the storage and evacuation functions of the following three organ systems: lower urinary tract, hindgut, and reproductive organs. In addition, it controls vascular resistance and capacitance. Thus the target tissues of the postganglionic neurons are vascular smooth muscle, visceral smooth muscles, probably secretory epithelia, and also neurons in the enteric nervous system and the pelvic ganglia. The preganglionic neurons are situated in the caudal part of the spinal representation, neurons associated with the colon being located rostral to those associated with the pelvic organs. Most lie medial to the classical intermediolateral cell column that may contain mainly vasoconstrictor neurons. Most (if not all) preganglionic neurons are cholinergic; some also contain an identified peptide. Most of the postganglionic neurons are situated in the inferior mesenteric ganglion (or equivalent structures); again, those projecting to the colon lie rostral to those projecting to the pelvic organs. Others lie in intercalated prevertebral ganglia, in the pelvic plexus, and in sacral paravertebral ganglia. The majority is noradrenergic, and most also contain one or several peptides, the topographical distribution of which appears to characterize functional subgroups of neurons. The terminations of noradrenergic axons in many pelvic organs probably make close contact with both vascular and nonvascular effectors. In the colon, most endings are located in the enteric plexuses. The responses of these organs to electrical stimulation of visceral nerves, and their reflex responses (together with those observed in the efferent axons of visceral nerve trunks) to electrical and natural stimulation of afferent fibers, lead to the general conclusion that several distinct classes of pre- and postganglionic neurons exist. 1) Vasoconstrictor neurons demonstrate ongoing activity with cardiac rhythm and appropriate reflexes to stimulation of cardiovascular afferent receptors and respond only weakly to natural stimulation of visceral receptors. 2) MR neurons respond to visceral stimuli but are not influenced from arterial baro- and chemoreceptors. These show at least two different response patterns consistent with their separate involvement in the reciprocal behavior of the colon and bladder. 3) Other neurons are silent in anesthetized animals and do not respond to any stimuli used thus far.(ABSTRACT TRUNCATED AT 400 WORDS)     

A study of the inferior mesenteric and pelvic ganglia of guinea-pigs with intracellular electrodes

1. Ganglion cells in the inferior mesenteric ganglion (IMG) and the pelvic plexus of the guinea-pig were studied using intracellular micro-electrodes.2. Ganglion cells had resting membrane potentials of 55-65 mV. Threshold for initiation of an action potential ranged from 10 to 20 mV depolarization. Action potentials often exceeded 100 mV in amplitude and were followed by an after-hyperpolarization of up to 20 mV.3. Synaptic responses were recorded from cells in the IMG in response to stimulation of the right and left hypogastric nerves, ascending mesenteric, inferior splanchnic and colonic nerves. It has been established that more than forty preganglionic fibres converge on any one cell. Preganglionic fibres to the IMG were also observed in the pelvic nerves.4. In contrast to the IMG, ganglion cells in the pelvic plexus received up to ten preganglionic fibres.5. Ganglion cells responded to supramaximal preganglionic stimulation with up to four action potentials.6. In the IMG, action potentials in response to synaptic action were followed by a prolonged period of hyperpolarization (after-hyperpolarization) and a later phase of prolonged depolarization (after-depolarization). The time course of these after potentials depended on the pattern of firing of action potentials during the period of stimulation. In the presence of dihydro-beta-erythroidine, or if synaptic action was insufficient to evoke action potentials, only the after-depolarization was observed.7. Other cells were impaled whose properties differed from those described above. In one group of cells the resting membrane potentials were higher (up to 85 mV), input resistances lower and the threshold for initiation of an action potential was higher. The other group were inexcitable, had high resting membrane potentials (up to 85 mV), low input resistances and underwent a slow depolarization in response to repetitive stimulation of preganglionic fibres.8. This study indicates that marked convergence of presynaptic fibres occurs on to ganglion cells of the IMG. The ganglion cells in the pelvic plexus receive a relatively small number of fibres, many of which exert intense synaptic activity ensuring a direct connexion to the central nervous system.     

一氧化氮合酶在大鼠主盆神经节及阴茎勃起组织中的分布

用ＮＡＤＰＨ脱氢酶组织化学方法观察了大鼠主盆神经节及阴茎勃起组织内一氧化氮合酶阳性成分的分布，发现主盆神经节内分布有大量ＮＯＳ阳性神经元，其中大部分密集于盆神经进入端，而膀胱端稀少，阴茎深动脉及其分支螺旋动脉周围，阴茎和尿道海绵体的平滑肌小梁内均分布有ＮＯＳ阳性纤维，阴茎勃起组织内未见ＮＯＳ阳性神经元，将光金注入阴茎海绵体后，在主盆神经节内发现有较多的荧光金标记细胞，结构ＮＡＤＰＨ反应，将荧光金注     

Localization of hindlimb vasomotor neurones in the lumbar spinal cord of the guinea pig

After retrograde labelling with horseradish peroxidase, sympathetic preganglionic neurones projecting to paravertebral ganglion cells with destinations primarily in the hindlimb were found to lie laterally in the intermediate region of the lumbar spinal cord. The majority of the labelled cell bodies were located near the edge of the grey matter or lateral to it within the white matter. In the most caudal segments (L3-L4) neurons extended right across the lateral funiculi. This distribution of neurones with predominantly vasoconstrictor functions differs markedly from that observed after labelling preganglionic fibres that project in the hypogastric nerve to the pelvic viscera.     

Facial nerve parasympathetic preganglionic afferents to the accessory otic ganglia by way of the chorda tympani nerve in the cat

 The distribution of accessory otic ganglia and connections between the ganglia and the chorda tympani nerve were investigated in the cat in order to determine the parasympathetic preganglionic facial nerve afferents to the otic ganglia using whole mount acetylthiocholinesterase (WATChE) histochemistry. The otic ganglia consist of a sigle main prominent ganglion and many small accessory ganglia lying on a plexus around the origins of the branches of the mandibular nerve and near the junction of the chorda tympani nerve and lingual nerve. In cell analysis of Nissl-stained preparations, the neurons composing the accessory otic ganglia were morphologically similar to the main otic ganglion neurons. Connecting branches from the chorda tympani nerve to the peripherally located acccessory otic ganglia were found and they were not stained by WATChE histochemistry. WATChE-positive connecting branches from the ganglia to the inferior alveolar, lingual, and mylohyoid nerves were also found in the same preparations. The WATChE histochemistry on various autonomic nervous tissues revealed that autonomic postganglionic nerve fibers are selectively stained darkly and that preganglionic fibers remain unstained. Therefore, it is considered that the WATChE-negative connections from the chordra tympani nerve consist chiefly of autonomic preganglionic fibers, whereas the WATChE-positive connections to the branches of the mandibular nerve are mainly postganglionic fibers. This suggests that some of the facial nerve parasympathetic preganglionic fibers in the chorda tympani nerve are mediated in the accessory otic ganglia and then join the branches of the mandibular nerve to supply the target mandibular tissues. Accepted: 25 November 1997     

Re-establishment of neurochemical coding of preganglionic neurons innervating transplanted targets

We investigated the effect on neurochemical phenotype of changing the targets innervated by sympathetic preganglionic neurons. In neonatal rats, the adrenal gland was transplanted into the neck, to replace the postganglionic neurons of the superior cervical ganglion. Transplanted adrenal glands survived, and contained noradrenergic and adrenergic chromaffin cells, and adrenal ganglion cells. Retrograde tracing from the transplants showed that they were innervated by preganglionic neurons that would normally have supplied postganglionic neurons of the superior cervical ganglion. The neurochemical phenotypes of preganglionic axons innervating transplanted chromaffin cells were compared with those innervating the normal adrenal medulla or superior cervical ganglion neurons. As in the normal adrenal gland, preganglionic nerve fibres apposing transplanted chromaffin cells were cholinergic. The peptide and calcium-binding protein content of preganglionic fibres was similar in normal and transplanted adrenal glands. In both cases, cholinergic fibres immunoreactive for enkephalin targeted adrenergic chromaffin cells, whilst cholinergic fibres with co-localised calretinin-immunoreactivity innervated noradrenergic chromaffin cells and adrenal ganglion cells. In contrast to the innervation of normal adrenal glands, these axons lacked immunoreactivity to nitric oxide synthase. In a set of control experiments, the superior cervical ganglion was subjected to preganglionic denervation in rat pups the same age as those that received adrenal transplants, and the ganglion was allowed to be re-innervated over the same time course as the adrenal transplants were studied. When the superior cervical ganglion was re-innervated by preganglionic nerve fibres, we observed that all aspects of chemical coding were restored, including cholinergic markers, nitric oxide synthase, enkephalin, calcitonin gene-related peptide and calcium binding proteins in predicted combinations, although the density of nerve fibres was always lower in re-innervated ganglia. These data show that the neurochemical phenotypes expressed by preganglionic neurons re-innervating adrenal chromaffin cells are selective and similar to those seen in the normal adrenal gland. Two explanations are advanced: either that contact of preganglionic axons with novel target cells has induced a switch in their neurochemical phenotypes, or that there has been target-selective reinnervation by pre-existing fibres of appropriate phenotype. Regardless of which of these alternatives is correct, the restoration of normal preganglionic codes to the superior cervical ganglion following denervation supports the idea that the target tissue influences the neurochemistry of innervating preganglionic neurons.     

Transmission from preganglionic fibres in the hypogastric nerve to peripheral ganglia of male guinea-pigs

1. Intracellular records were obtained from ganglion cells of the pelvic plexus of male guinea-pigs.2. The input resistance of cells which responded to intracellular stimulation varied from 40 to 150 MOmega. Slope resistance decreased when the membrane was hyperpolarized. Time constants varied from 5 to 200 msec. Resting membrane potentials ranged from 40 to 70 mV.3. Action potentials in response to direct stimulation were followed by a prolonged phase of after-hyperpolarization.4. A second type of cell was also impaled which did not respond to electrical stimulation. These cells had resting membrane potentials in the range 60-70 mV, input resistances of less than 20 MOmega and time constants of less than 3 msec.5. In most ganglion cells, stimulation of the hypogastric nerve evoked action potentials which were often followed by a secondary phase of depolarization indicating continuing transmitter action.6. Orthodromic responses were generally ;all-or-nothing' and could not be graded with changes in stimulus strength. The latency of orthodromic responses indicated that ganglion cells were innervated by both B and C fibres in the hypogastric nerve.7. Orthodromic responses were blocked by tubocurarine, 5 x 10(-5) g/ml., and dihydro-beta-erythroidine, 10(-5) g/ml.8. Spontaneous, excitatory post-synaptic potentials of up to 4.8 mV in amplitude were observed. The frequency of their discharge was greatly increased by repetitive stimulation of the hypogastric nerve.9. The ultrastructure of the pelvic ganglia was studied by electronmicroscopy. Two types of ganglion cell process were observed, fine (0.1 mu) branching tufts thrown up from the soma within the surrounding capsule and longer, thicker (1 mu) extracapsular processes. Synapses were found to occur most frequently between the varicose terminal segments of preganglionic axons and the small intracapsular processes.10. Similarities between the properties of the pelvic ganglia innervated by the hypogastric nerve and those of the parasympathetic division of the autonomic nervous system are discussed.