Organization of the guinea-pig uterine innervation. Distribution of immunoreactivities for different neuronal markers. Effects of chemical- and pregnancy-induced sympathectomy

Summary The structural organization of the guinea-pig uterine innervation was investigated by an immunofluorescence method using neurofibrillary protein (NF) and neuron-specific enolase (NSE) as general neuronal markers. NF- and NSE-immunoreactive nerve trunks and non-varicose nerves formed continuous networks similar to nerves with analogue morphology and with immunoreactivities for tyrosine hydroxylase (TH; adrenergic nerves) and neuropeptide Y (NPY). NF- and NSE-immunoreactive non-varicose nerves occurred in the myometrium and along vessels, where TH- and NPY-immunoreactive varicose nerves were also comparatively frequent. After chemical sympathectomy all TH- and NPY-immunoreactive varicose nerves and most NF- and NSE-immunoreactive non-varicose nerves disappeared, suggesting colocalization of TH, NPY, NF and NSE immunoreactivities. During pregnancy all NF-, NSE-, TH- and NPY-immunoreactive nerve structures disappeared in the foetus-bearing uterine horns whereas in the cervix and non-foetus-bearing uterine horns only the myometrial TH- and NPY-immunoreactive varicose nerves disappeared. After parturition there was a complete structural restoration of all types of immunoreactive nerves in previously non-foetus-related tissue. The reinnervation of this tissue followed a similar time-course to that after chemical sympathectomy. In contrast, the reinnervation of previously foetus-related tissue was much slower and incomplete.In conclusion, the whole autonomic uterine innervation undergoes overt structural changes during pregnancy and these changes are related to the foetus-bearing regions.     

Ontogenetic development of the guinea pig uterine innervation. An immunohistochemical study of different neuronal markers, neuropeptides and S-100 protein

The ontogenetic development of the guinea pig uterine autonomic innervation was studied immunohistochemically using neurofibrillary protein (NF) and neuron specific enolase (NSE) as general neuronal markers, tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) as specific markers for adrenergic innervation and S-100 protein as marker for Schwann cell structure and/or function. In addition, comparisons were made of the development of the different populations of peptide-containing nerves. The structure and time of appearance were similar for nerves with NF-, NSE-, TH- and DBH-immunoreactivities, which were first present in the organ periphery as coarse nerve trunks, then extending centrally and branching into non-varicose nerves. From these, varicose nerves developed first in relation to vessels and then in association with the myometrial smooth musculature. Development was completed earlier in the cervix than in the uterine horns suggesting differences in local environment. In comparison, S-100 nerve-immunoreactivity appeared later but attained complete development more rapidly than axonal structures. Neuropeptide Y-immunoreactive nerves showed a similar developmental pattern to presumed adrenergic nerves, further verifying the assumption of intraneuronal localization of NPY in uterine adrenergic nerves. Other peptide-containing nerves were developed later probably reflecting differences in neuronal growth properties.     

S-100-immunoreactive nerves in the guinea-pig uterus with reference to ultrastructural correlations: Effects of chemical sympathectomy and pregnancy

Summary In the guinea-pig uterus, by use of an indirect immunofluorescence method, S-100 immunoreactivity was found to be restricted to nerves that corresponded in number, distribution and type to adrenergic axons and preterminals. With advancing pregnancy S-100 immunoreactivity completely disappeared in uterine tissue adjacent to a fetus, in parallel with an ultrastructural degeneration of the adrenergic innervation. In the cervix and the uterine horn devoid of a fetus, however, the number and distribution of S-100-immunoreactive nerves was seemingly unchanged and no ultrastructural changes were found in adrenergic nerves. In contrast, chemical sympathectomy produced by 6-hydroxydopamine did not change S-100 immunoreactivity of uterine nerves. These findings suggest that there are differences in the denervation effected by chemical and by pregnancy-induced sympathectomy. The latter probably represents a special type of adrenergic denervation by inducing a degeneration of Schwann cells in addition to destruction of neuronal structures. This may explain the differences in the speed of regeneration of uterine adrenergic nerves following the two types of denervation.     

Ontogenetic development of the guinea pig uterine innervation

Summary The ontogenetic development of the guinea pig uterine autonomic innervation was studied immunohistochemically using neurofibrillary protein (NF) and neuron specific enolase (NSE) as general neuronal markers, tyrosine hydroxylase (TH) and dopamine -hydroxylase (DBH) as specific markers for adrenergic innervation and S-100 protein as marker for Schwann cell structure and/or function. In addition, comparisons were made of the development of the different populations of peptide-containing nerves.The structure and time of appearance were similar for nerves with NF-, NSE-, TH- and DBH-immunoreactivities, which were first present in the organ periphery as coarse nerve trunks, then extending centrally and branching into non-varicose nerves. From these, varicose nerves developed first in relation to vessels and then in association with the myometrial smooth musculature. Development was completed carlier in the cervix than in the uterine horns suggesting differences in local environment. In comparison, S-100 nerve-immunoreactivity appeared later but attained complete development more rapidly than axonal structures. Neuropeptide Y-immunoreactive nerves showed a similar developmental pattern to presumed adrenergic nerves, further verifying the assumption of intraneuronal localization of NPY in uterine adrenergic nerves. Other peptide-containing nerves were developed later probably reflecting differences in neuronal growth properties.     

Protein gene product 9.5 (PGP 9.5)

Summary The guinea pig uterus is supplied by different populations of nerves which can be demonstrated by specific immunocytochemical and histochemical techniques. So far, there has been no single marker displaying entire peripheral innervation patterns. Recently, protein gene product (PGP) 9.5, a cytoplasmic protein in neurons and neuroendocrine cells, was found to visualize both different populations and subtypes of nerves. This prompted the present study of using PGP 9.5 for visualization of the whole uterine innervation. This was performed by the indirect immunofluorescence method using antiserum to PGP 9.5 raised in rabbits.PGP-immunoreactivity was present in all neuronal parts of the extrinsic and intrinsic uterine innervation, including different subpopulations of nerves. This was verified by chemical sympathectomy and sensory denervation with 6-hydroxydopamine and capsaicin-treatment respectively, and double immunostaining.By term a disappearance of uterine PGP-nerve-immunoreactivity was observed which was almost complete in fetus-bearing uterine tissue and further strengthens previous assumptions of a general, pregnancy-induced uterine neuronal degeneration.The developmental time-course and morphology of PGP-immunoreactive nerve structures was similar to that for other neuronal markers and support the suggestion of PGP-immunoreactivity as a general marker for the entire uterine innervation, and suggests that the presence of PGP 9.5-immunoreactivity may coincide with functional maturation of uterine innervation.     

Effects of infantile/prepubertal chronic estrogen treatment and chemical sympathectomy with guanethidine on developing cholinergic nerves of the rat uterus.

The innervation of the uterus is remarkable in that it exhibits physiological changes in response to altered levels in the circulating levels of sex hormones. Previous studies by our group showed that chronic administration of estrogen to rats during the infantile/prepubertal period provoked, at 28 days of age, an almost complete loss of norepinephrine-labeled sympathetic nerves, similar to that observed in late pregnancy. It is not known, however, whether early exposure to estrogen affects uterine cholinergic nerves. Similarly, it is not known to what extent development and estrogen-induced responses in the uterine cholinergic innervation are affected by the absence of sympathetic nerves. To address this question, in this study we analyzed the effects of infantile/prepubertal chronic estrogen treatment, chronic chemical sympathectomy with guanethidine, and combined sympathectomy and chronic estrogen treatment on developing cholinergic nerves of the rat uterus. Cholinergic nerves were visualized using a combination of acetylcholinesterase histochemistry and the immunohistochemical demonstration of the vesicular acetylcholine transporter (VAChT). After chronic estrogen treatment, a well-developed plexus of cholinergic nerves was observed in the uterus. Quantitative studies showed that chronic exposure to estrogen induced contrasting responses in uterine cholinergic nerves, increasing the density of large and medium-sized nerve bundles and reducing the intercept density of fine fibers providing myometrial and perivascular innervation. Estrogen-induced changes in the uterine cholinergic innervation did not appear to result from the absence/impairment of sympathetic nerves, because sympathectomy did not mimic the effects produced by estrogen. Estrogen-induced responses in parasympathetic nerves are discussed, considering the direct effects of estrogen on neurons and on changes in neuron-target interactions.     

Surgical ablation of oviductal extrinsic innervation changes GABA levels in the rat fallopian tube

The origin of gamma-aminobutyric acid (GABA) in the rat oviduct was investigated by measuring GABA levels in the oviduct after selective ablation of the extrinsic oviductal innervation. Rats killed 20 days after ablation of nerves connected with the left oviduct showed no differences in GABA levels in the left vs the right oviduct. Rats killed 50 days after ablation of the left ovarian vascular nerve bundle showed a decreased GABA content in the left vs the right (intact) oviduct which was more pronounced in rats killed 90 days after ablation. In contrast, GABA levels were unchanged 50 days after ligation of either the suspensory ligament of the ovary or the uterine artery. Our results indicate the involvement of a GABAergic component in the extrinsic innervation of the rat oviduct.     

Regional difference in the distribution of vasoactive intestinal polypeptide-immunoreactive nerve fibres along the uterus and between myometrial muscle layers in the rat

To investigate a possible regional variation of the vasoactive intestinal polypeptide innervation in the uterus of the cyclic rat, the distribution of vasoactive intestinal polypeptide-containing nerve fibres from the cervix to the oviduct end of the uterine horns was studied using immunohistochemistry. Immunoreactive nerve fibres were most concentrated in the cervix, where they formed a dense plexus in association with the musculature and surrounding blood vessels. In the uterus, a clear regional distribution of the vasoactive intestinal polypeptide innervation was observed. Numerous vascular and non-vascular immunoreactive nerve fibres were present in the lower part of the uterine horns, whereas they were sparse in the median region and absent at the oviduct end. Moreover, non-vascular peptide innervation was mostly concentrated in the circular layer of the myometrium and also occurred in the endometrium. Only a very few immunoreactive nerve fibres were presen t in the longitudinal muscle layer. No change in the peptide innervation pattern was observed during the different stages of the sexual cycle. The marked regional distribution of the peptide innervation in the rat uterus suggests that the regulatory effects of the peptide occur mainly in the lower part of the organ and principally affect the circular muscle layer in the myometrium.     

Wallerian degeneration and axonal regeneration after sciatic nerve crush are altered in ICAM-1-deficient mice

The intercellular cell adhesion molecule-1 (ICAM-1) has been implicated in the recruitment of immune cells during inflammatory processes. Previous studies investigating its involvement in the process of Wallerian degeneration and focusing on its potential role in macrophage recruitement have come to controversial conclusions. To examine whether Wallerian degeneration is altered in the absence of ICAM-1, we have analyzed changes in the expression of axonal and Schwann cell markers following sciatic nerve crush in wildtype and ICAM-1-deficient mice. We report that the lack of ICAM-1 leads to impaired axonal degeneration and regeneration and to alterations in Schwann cell responses following sciatic nerve crush. Degradation of neurofilament protein, the collapse of axonal profiles, and the re-expression of neurofilament proteins are substantially delayed in the distal nerve segment of ICAM-1^-/- mice. In contrast, the degradation of myelin, as determined by immunostaining for myelin protein zero, is unaltered in the mutants. Upregulation of GAP-43 and p75 neurotrophin receptor (p75^NTR) expression, characteristic for Schwann cells dedifferentiating in response to nerve injury, is differentially altered in the mutant animals. These results indicate that ICAM-1 is essential for the normal progression of axonal degeneration and regeneration in distal segments of injured peripheral nerves.     

Noradrenergic and acetylcholinesterase-positive nerve fibres of the uterus in sexually immature and cycling rats

Summary The distribution and density of the noradrenergic and acetylcholinesterase-positive nerve fibres were histochemically studied in different uterine regions of prepubertal and cycling rats in dioestrus and oestrus. Besides the rich and double innervation of blood vessels, both types of nerve fibre were found in the myometrium and cervical musculature. The non-vascular noradrenergic network looked denser at the tubal end of the horns and at the cervix, whereas the acetylcholinesterase-positive innervation was poor at the tubal end, increasing toward the cervix. Contrasting with the middle third of the uterine horn, at the tubal end, the myometrial longitudinal layer was much more innervated than the circular one, especially by the noradrenergic nerve fibres. The prepubertal rats presented an adult pattern of uterine autonomic innervation. In the cycling animals, this innervation was nearly the same during oestrus and dioestrus regarding both the density of nerve fibres and intensity of the histochemical reactions.     

Extrinsic cellular and molecular mediators of peripheral axonal regeneration

The ability of injured peripheral nerves to regenerate and reinnervate their original targets is a characteristic feature of the peripheral nervous system (PNS). On the other hand, neurons of the central nervous system (CNS), including retinal ganglion cell (RGC) axons, are incapable of spontaneous regeneration. In the adult PNS, axonal regeneration after injury depends on well-orchestrated cellular and molecular processes that comprise a highly reproducible series of degenerative reactions distal to the site of injury. During this fine-tuned process, named Wallerian degeneration, a remodeling of the distal nerve fragment prepares a permissive microenvironment that permits successful axonal regrowth originating from the proximal nerve fragment. Therefore, a multitude of adjusted intrinsic and extrinsic factors are important for surviving neurons, Schwann cells, macrophages and fibroblasts as well as endothelial cells in order to achieve successful regeneration. The aim of this review is to summarize relevant extrinsic cellular and molecular determinants of successful axonal regeneration in rodents that contribute to the regenerative microenvironment of the PNS.     

The origin and distribution of adrenergic nerve fibres in the guinea-pig colon

Summary A detailed study of the origin and distribution of sympathetic fibres in the distal colon of the guinea-pig has been made using the fluorescent histochemical method for localizing catecholamines. The extrinsic adrenergic fibres of the colonie sympathetic nerves follow the inferior mesenteric artery and its branches to the colon. Some of the extrinsic adrenergic fibres are associated with the parasympathetic fibres of the pelvic nerves near the colon. Complete adrenergic denervation follows the removal of the inferior mesenteric ganglion or the destruction of the nerves running with the inferior mesenteric artery.No fluorescent fibres, other than those associated with blood vessels, were observed in air-dried stretch preparations of the isolated longitudinal muscle. However, a substantial number of varicose, terminal fibres, not associated with blood vessels, were observed in the circular muscle. Some varicose fibres, apart from those associated with ganglion cells, were observed in the myenteric plexus. These fibres were seen in the bundles of nerves running between the nodes of the plexus and also as single fibres which branched from the plexus to end in areas free of ganglion cells.Three plexuses of adrenergic nerve fibres have been distinguished in the submucosa: a dense plexus of terminal fibres innervating both the veins and arteries; a plexus consisting of innervated nodes of ganglion cells, connected by bundles of fluorescent and non-fluorescent nerves; and a plexus of varicose and non-varicose fibres, which is not associated with ganglion cells. Some groups of ganglion cells in the submucosa were without adrenergic innervation.A plexus of varicose fibres forms a meshwork in the lamina propria of the mucosa. The muscularis mucosae is sparsely innervated. Most of the blood vessels in the mucosa are not associated with adrenergic fibres.     

Pregnancy reduces noradrenaline but not neuropeptide levels in the uterine artery of the guinea-pig

Summary Using histochemical, immunohistochemical and biochemical techniques, noradrenaline-, neuropeptide Y-, vasoactive intestinal polypeptide-, substance P- and calcitonin gene-related peptide-containing nerve fibres were studied in the uterine artery of virgin, progesterone-treated and pregnant guinea-pigs. Morphological changes following hormone treatment or in pregnancy were also evaluated in a quantitative study on semithin sections of the uterine artery. In late pregnancy, the number of noradrenalinecontaining nerve fibres, which formed the densest plexus in virgin animals, was significantly decreased, a finding supported by a significant reduction in noradrenaline levels. This reduction was not mimicked by systemic progesterone treatment. In contrast, the innervation of the uterine artery by neuropeptide Y-containing nerve fibres was increased in pregnancy, while the other peptidergic nerves and peptide levels were unchanged after progesterone treatment and in pregnancy. These changes led to a predominance of innervation by neuropeptide Y- rather than noradrenaline-containing nerve fibres in late pregnancy. No morphological changes were detected following progesterone treament, but pregnancy led to a marked increase in the cross-sectional area of the vessel accompanied by an increase in the thickness of the media.     

Plasticity in developing rat uterine sensory nerves: the role of NGF and TrkA

In the present study we investigated the effects of infantile/prepubertal chronic oestrogen treatment, chemical sympathectomy with guanethidine and combined sympathectomy and chronic oestrogen treatment on developing sensory nerves of the rat uterus. Changes in sensory innervation were assessed quantitatively on uterine cryostat tissue sections stained for calcitonin gene-related peptide (CGRP). Uterine levels of NGF protein, using immunohistochemistry and ELISA, and mRNA, using Northern blots and in situ hybridization, were also measured. Finally, levels of TrkA NGF receptor in sensory neurons of T13 and L1 dorsal root ganglia (DRG), which supply the uterus, were assessed using densitometric immunohistochemistry. These studies showed that: (1) chronic oestrogen treatment led to an 83% reduction in the intercept density of CGRP-immunoreactive nerves; (2) sympathectomy had no effect on the density of uterine sensory nerves or on the pattern of oestrogen-induced changes; (3) NGF mRNA and protein increased following sympathectomy or chronic oestrogen treatment; and (4) oestrogen produced increased intensity of labelling (28%) for TrkA receptors in small-diameter sensory neurons, but decreased labelling (13%) in medium-sized neurons, which represent the large majority of the DRG neurons supplying the upper part of the uterine horn. Contrary to expectations, increased levels of NGF after sympathectomy and oestrogen treatment did not lead to increased sensory innervation of the uterus. The possibility that alterations in neuronal levels of TrkA contribute to the lack of response of uterine sensory nerves to the oestrogen-induced increase in NGF levels is discussed.This work was supported by The Wellcome Trust, UK (CRIG Grant 058122/Z/99/Z/JC/KO), and PEDECIBA, Universidad de la República, Montevideo, Uruguay     

Differential effects of oestrogen on developing and mature uterine sympathetic nerves

Oestrogen is a key factor in the remodelling of uterine sympathetic nerves during puberty and the oestrous cycle; these nerves are influenced by changes in their target uterine tissue. The magnitude of oestrogen-induced responses might however be influenced by the maturation stage of sympathetic nerve fibres, the age of the neurons and/or the developmental state of the uterus. We have therefore compared the sympathetic innervation of the uterus following chronic oestrogen treatment of infantile/prepubertal and young adult intact and ovariectomised rats. Treatment of infantile/prepubertal rats resulted in the complete loss of intrauterine noradrenaline (NA)-labelled sympathetic nerves and a marked reduction in the total NA content in the uterine horn. Chronic treatment of young adult rats had little effect. To examine whether the age of the neurons or the degree of development of the uterus determined responsiveness of nerves to oestrogen, we assessed the effects of oestrogen on the sympathetic reinnervation of intraocular transplants of young adult uterine myometrium into ovariectomised adult host rats. Early treatment (10 days post-transplantation) resulted in less sympathetic innervation than late treatment (30 days post-transplantation). Measurements of nerve growth factor (NGF) levels in the uterine horn of control rats before and after puberty and following infantile/prepubertal chronic oestrogen treatment and acute oestrogen treatment of young adult rats revealed a coordinated increase between the growth of the uterus and NGF protein levels. Thus, developing and recently regrown sympathetic nerves are more susceptible to oestrogen-induced changes in the uterus than mature nerves, differential susceptibility is not related to the age of the neurons or the developmental state of the uterus and changes in NGF protein do not account for the differential susceptibility of developing and mature uterine sympathetic nerve fibres to oestrogen. Growing sympathetic fibres are more vulnerable to oestrogen than mature fibres and nerve fibres that have been in contact for longer periods with their target become less susceptible to oestrogen.     

Avian enteric nerve plexuses

Summary The enteric nerve plexuses of the domestic fowl (Gallus domesticus) were investigated in sections and stretch preparations by means of the cholinesterase and glyoxylic acid fluorescence histochemical techniques. Cholinesterase-positive and varicose and non-varicose fluorescent nerve fibres were distributed at all levels of the gut in myenteric, submucosal, muscle and mucosal plexuses, and in a perivascular plexus. The density of the innervation and the detailed distribution of the nerves varied in different parts of the intestinal tract. All nerve plexuses appeared to be best developed in the rectum. Whereas the circular muscle coat contained a substantial number of nerves at all levels of the gut, the longitudinal coat was well innervated only in the rectum. The major portion of the mucosal plexus appeared to be associated with the intestinal glands. The nerve cell bodies were restricted to the myenteric and submucosal plexuses and were mainly cholinesterase-positive. Fluorescent ganglion cells were not observed. Pretreatment of stretch preparations with NADH: Nitro BT to stain ganglion cells showed that the majority of the cells were surrounded by a meshwork of fluorescent varicose fibres, although none of the fibres appeared to be associated with individual cells. The perivascular plexus was mainly associated with the arteries. The functional significance of the innervation is discussed.We would like to thank the British Council for financial support for Mr. H.A. Ali     

Hepatocyte innervation in primates

The efferent innervation and some characteristics of nerve fibers of the liver lobule in the tree shrew, a primate, are described. Nerve endings on hepatocytes were encountered regularly and were determined to be efferent adrenergic nerves. Transmission electron microscopy revealed nerve endings and varicosities in close apposition to the hepatocytes adjacent to the connective tissue of the triads as well as within the liver lobule in the space of Disse. Fluorescence microscopy indicated the existence of adrenergic nerves with a similar distribution. Autoradiography of the avid uptake of exogenous [3H]norepinephrine indicated that all intralobular nerves are potentially norepinephrinergic (adrenergic). Chemical sympathectomy with 6-OH-dopamine resulted in the degeneration of all intralobular liver nerve fibers as revealed by fluorescence microscopy and electron microscopy. Substantial regeneration occurred after 60-90 days but was not completed by that time. Some nerves were also observed in close association with von Kupffer cells and endothelial cells. The functional significance of the efferent liver innervation is discussed.     

Distribution of Peptide-Containing Neurons in the Developing Rat Right Atrium,Studied Using Immunofluorescence and Confocal Laser Scanning

The developmental pattern and distribution of peptide-containing neurons in the rat heart right atrium has been studied by indirect immunofluorescence. Antibodies against neuropeptide Y (NPY), substance P (SP), and vasoactive intestinal polypeptide (VIP) were applied to whole-mount stretch preparations of the right atria from hearts of newborn to 40-day-old animals. NPY-like immunoreactivity (LI) was compared with the synaptic vesicle marker SV2 in double immunoincubation studies. The distribution of immunofluorescence was studied by confocal laser scanning microscopy. NPY-LI and SP-LI were present throughout the atria already at birth, in contrast to VIP-LI that was observed at day 10. The postnatal changes of innervation were basically quantitative, with an increase in density of nerve fibres and number of varicosities, while the basic pattern of innervation was essentially established during the first 1–10 days. NPY- and SP-positive bundles of fibres appeared to enter the right atrium along the superior caval vein, having extrinsic origins. Nerve fibres with NPY-LI colocalized in most nerve terminals with SV2-LI, and showed a developmental pattern similar to that observed for adrenergic neurons earlier. These NPY/SV2 positive fibres probably represent the extrinsic NPY innervation. In addition, NPY-LI was identified in large intrinsic nerve cells bodies located near the atrioventricular (AV) region. Most of the VIP-LI was observed in short nerve fibres originating in intrinsic VIP-positive cell bodies, but a few apparently extrinsic VIP-positive fibres were found, probably representing preganglionic parasympathetic neurons. SP in the atria was probably of extrinsic (sensory) origin and no nerve cell bodies with SP-LI were detected. The results show that the peptidergic innervation in the developing rat right atrium involves both extrinsic and intrinsic peptidergic neurons which may participate in the regulation of neurotransmission in local neuronal circuits.     

Pituitary adenylate cyclase-activating polypeptide in intrinsic and extrinsic nerves of the rat pancreas

Pituitary adenylate cyclase-activating polypeptide (PACAP) is the latest member of the vasoactive intestinal polypeptide (VIP) family of neuropeptides present in nerve fibres in many peripheral organs. Using double immunohistochemistry, with VIP as a marker for intrinsic innervation and calcitonin-gene related peptide (CGRP) as a marker for mainly extrinsic innervation, the distribution and localization of PACAP were studied in the rat pancreas. PACAP was demonstrated in nerve fibres in all compartments of the pancreas and in a subpopulation of intrapancreatic VIP-containing ganglion cells. PACAP and VIP were co-stored in intra- and interlobular nerve fibres innervating acini, blood vessels, and in nerve fibres within the islets of Langerhans. No PACAP immunoreactivity was observed in the islet cells. Another population of PACAP-immunoreactive nerve fibres co-localized with CGRP innervated ducts, blood vessels and acini. PACAP/CGRP-positive nerve fibres were also demonstrated within the islets. Neonatal capsaicin reduced the PACAP-38 concentration by approximately 50%, and accordingly a marked reduction in PACAP/CGRP-immunoreactive nerve fibres in the exocrine and endocrine pancreas was observed. Bilateral subdiaphragmatic vagotomy caused a slight but significant decrease in the PACAP-38 concentration compared with controls. In conclusion, PACAP-immunoreactive nerve fibres in the rat pancreas seem to have dual origin: extrinsic, most probably sensory fibres co-storing CGRP; and intrinsic, constituting a subpopulation of VIP-containing nerve cell bodies and fibres innervating acinar cells and islet cells. Our data provide a morphological basis for the reported effects of PACAP in the pancreas and suggest that PACAP-containing nerves in the rat pancreas may have both efferent and sensory functions.     

Degeneration of adrenergic nerves in the urinary bladder during pregnancy

The adrenergic innervation of the urinary bladder of normal female and pregnant rats has been studied using a fluorescence histochemical method. The bladder is richly innervated by adrenergic nerve fibres as is evidenced by the presence of numerous adrenergic nerves in the adventitia, musculosa and submucosa. However, adrenergic nerve cells could not be observed. During pregnancy, adrenergic nerve fibres showed signs of degeneration, as most of the nerve fibres disappeared and the surviving fibres were much swollen. 10 days after parturition the pattern and density of adrenergic innervation became almost similar to those of the control animals.