Jean-Paul Rousseau

SYMPATHETIC INNERVATION OF THE UPPER AND LOWER REGIONS OF THE UTERUS AND CERVIX IN THE RAT HAVE DIFFERENT ORIGINS AND ROUTES

The origins and routes of the postganglionic sympathetic nerve supply to the upper and lower uterus and to the cervix were investigated in the rat by using denervation procedures combined with immunohistochemistry and retrograde tracing. The sympathetic nerve fibers of the upper part of the uterus arise from the ovarian plexus nerve. They mainly originate (90%) from neurons of the suprarenal ganglia (SRG) and of the T10 to L3 ganglia of the paravertebral sympathetic chain. Fluoro‐Gold injections into different regions of the upper uterus showed that the SRG neurons mainly provide innervation to the tubal extremity (52%) rather than to the uterine portion below this area (26%). Very few neurons of the celiac ganglion or the aorticorenal ganglia participated in this innervation. Most of the sympathetic innervation of the lower uterus and the cervix (90%) originates from neurons of the paravertebral ganglia T13 to S2, principally at the L2–L4 levels. By using immunocytochemistry, we show that very few tyrosine hydroxylase–positive neurons of the pelvic plexus project to these areas, where they represent only 3% of the sympathetic nerve supply. Again, very few neurons of the inferior mesenteric ganglion (IMG) supply the lower uterus and the cervix. The comparison between retrograde tracing experiments in intact animals and after the removal of the IMG shows that very few sympathetic postganglionic axons from the paravertebral chain pass through the IMG to reach the lower uterus and the cervix. In contrast, these axons mainly project to splanchnic nerves bypassing the IMG to connect with the hypogastric nerves. In addition, some axons supplying the lower uterus follow the superior vesical arteries and then reach the organ. Taken together, these results show that the upper region of the uterus receives a sympathetic innervation that is different in origin and route from that of the lower uterus and the cervix. Such a marked region‐specific innervation suggests that nerve control of the myometrial activity may be functionally different between the oviduct and the cervical ends of the uterus. J. Comp. Neurol. 399:403–412, 1998.

A large proportion of pelvic neurons innervating the corpora cavernosa of the rat penis exhibit NADPH-diaphorase activity

Nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry, which indicates the presence of neural nitric oxide synthase, the enzyme responsible for the generation of nitric oxide, was used in combination with retrograde labelling methods to determine, in whole-mounts and sections of rat major pelvic ganglia, whether neurons destined for the penile corpora cavernosa were able to produce nitric oxide. In whole-mount preparations of pelvic ganglia, among the 607±106 retrogradely labelled neurons innervating the penile corpora cavernosa, 84±7% were NADPH-diaphorase-positive, 30±7% of which were intensely histochemically stained. In serial sections of pelvic ganglia, out of a mean count of 451 retrogradely labelled neurons, 65% stained positively for NADPH-diaphorase. An average of 1879±363 NADPH-diaphorase positive cell bodies was counted in the pelvic ganglion. In the major pelvic ganglion, neurons both fluorescent for Fluorogold or Fast Blue and intensely stained for NADPH-diaphorase were consistently observed in the dorso-caudal part of the ganglia in the area close to the exit of the cavernous nerve and within this nerve. This co-existence was much less constant in other parts of the ganglion. In the rat penis, many NADPH-diaphorase-positive fibres and varicose terminals were observed surrounding the penile arteries and running within the wall of the cavernous spaces. This distribution of NADPH-diaphorase-positive nerve cells and terminals is consistent with the idea that the relaxation of the smooth muscles of the corpora cavernosa and the dilation of the penile arterial bed mediated by postganglionic parasympathetic neurons is attributable to the release of nitric oxide and that nitric oxide plays a crucial role in penile erection. Moreover, the existence in the pelvic ganglion of a large number of NADPH-diaphorase-positive neurons that are not destined for the corpora cavernosa suggests that nitric oxide is probably also involved in the function of other pelvic tissues.

Small intensely fluorescent cells of the rat paracervical ganglion synthesize adrenaline, receive afferent innervation from postganglionic cholinergic neurones, and contain muscarinic receptors.

In the paracervical ganglion (PCG) of the rat, double-labelling immunofluorescence for catecholamine-synthesizing enzymes and HPLC measurement of catecholamine contents were first performed to evaluate whether intraganglionic small intensely fluorescent (SIF) cells are capable of synthesizing adrenaline. Immunolabelling for tyrosine hydroxylase (TH), dopamine beta-hydroxylase and phenylethanolamine-N-methyl transferase (PNMT) occurred in all SIF cells of the PCG, thus demonstrating the presence of all the enzymes required for adrenaline biosynthesis. Adrenaline levels were undetectable in the PCG but to test the hypothesis that PNMT is active in SIF cells, catecholamines were measured in ganglia of rats pretreated with pargyline, an inhibitor of the monoamine oxidase, the major enzyme involved in the catecholamine degradation. Pargyline treatment increased adrenaline levels in the PCG, thus demonstrating that SIF cells are capable of adrenaline synthesis. The undetectable levels of adrenaline in the PCG of untreated rats suggested a slow rate of biosynthesis of adrenaline in the ganglion. Furthermore, the use of double-labelling showed that SIF cells of the PCG were stained for muscarinic receptors and were approached by varicose ChAT-immunoreactive nerve fibres. Nerve fibres immunoreactive for ChAT were also observed associated with nerve cell bodies of ganglion neurones. Following deafferentation of the PCG, the ChAT-immunoreactive nerve fibres surrounding nerve cell bodies totally disappeared indicating their preganglionic origin, while those associated with SIF cells did not degenerate, which demonstrate that they derived from intraganglionic cholinergic neurones. Taken together, the results show that adrenaline may be a transmitter for SIF cells in the PCG and suggest that cholinergic neurones of the parasympathetic division of the PCG can modulate the SIF cell activity through the activation of muscarinic receptors.

Distribution of noradrenergic neurons in the female rat pelvic plexus and involvement in the genital tract innervation

The involvement of the pelvic plexus noradrenergic neurons in the innervation of the genital tract was studied in the female rat. Several small ganglia were observed in addition to the paracervical ganglion and immunocytochemistry for tyrosine hydroxylase was performed to examine the distribution and number of the noradrenergic neurons. 5069 +/- 1525 nerve cell bodies were counted in the paracervical ganglion and 9.0 +/- 0.8% of them were noradrenergic, displaying a clear somatotopic distribution in the ventro-medial part of the ganglion. Some accessory ganglia were located ventral to the main paracervical ganglion. 414 +/- 149 nerve cell bodies were found in the accessory ganglia, of which 20.4 +/- 3.1% were noradrenergic. Ganglia along the vesical branch of the hypogastric nerve, referred to as an hypogastric plexus, contained 233 +/- 83 neurons among which 12.7 +/- 7.2% were noradrenergic. Bilateral removal of the pelvic plexus produced degeneration of all the tyrosine hydroxylase-immunoreactive nerve fibres in the lower part of the uterus and in the cervix. In contrast, excision of the paracervical ganglia and the accessory ganglia caused no significant change in this innervation pattern. Combined retrograde tracing study and immunocytochemistry for tyrosine hydroxylase revealed a very small number of noradrenergic neurons also labelled with fluoro-Gold. Both findings suggest a limited involvement of the pelvic plexus noradrenergic neurons in the innervation of the lower genital tract.

Coexpression of neuropeptide Y and vasoactive intestinal polypeptide in pelvic plexus neurones innervating the uterus and cervix in the rat

Abstract.The present study investigates the distribution and coexpression of neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) in neurones of the accessory ganglion (AG), hypogastric plexus (HP) and paracervical ganglion (PCG), which compose the pelvic plexus in the female rat. Nerve cell bodies immunoreactive for NPY and VIP represent 84% and 46% of the neurone population in the PCG, respectively, while immunoreactivity for each peptide is observed in about 90% of the AG and HP neurones. Adjacent sections immunostained for NPY and VIP, as well as the use of immunocytochemistry combined with in situ hybridization show that 92% of the VIP-containing neurones in the pelvic plexus also contain NPY. In addition, a retrograde tracing study performed in combination with immunocytochemistry demonstrates that pelvic plexus neurones project preferentially to the lower part of the uterus and to the cervix, and that about 95% of these projecting neurones contain VIP. Taken together, our findings indicate that in the female rat, neurones of the pelvic plexus projecting to the lower genital tract mainly coexpress VIP and NPY, and supply nerve fibres to the vascular and nonvascular smooth muscle in the uterocervical region. Since NPY and VIP exert distinct effects according to the target tissue, our results suggest that neurones coexpressing these peptides play important roles in the local regulation of the vascular bed and motor activity of the lower genital tract.

Involvement of the pelvic plexus and the suprarenal ganglia in the neuropeptide Y (NPY) innervation of the cervix and the uterus of the rat

The involvement of the pelvic plexus and suprarenal ganglia in the neuropeptide Y (NPY) innervation of the genital tract was studied in the female rat by means of denervation experiments and retrograde tracing studies. Removal of the paracervical ganglia caused a significant decrease of the NPY-immunoreactive nerve density and NPY concentration in the lower part of the genital tract: cervix, uterine body and lower part of the uterine horn. The decrease in NPY concentration in these three regions was more pronounced after lesion of the pelvic plexus. Lesion of the ovarian nerve plexus caused a depletion in the NPY-immunoreactive nerve fibres and a decrease in NPY concentration in the upper part of the uterine horn. Pelvic nerve section, inferior mesenteric ganglia excision and superior ovarian nerve section had no effect on the NPY innervation in the genital tract. Injection of fluorogold into the cervix and lower part of the uterus combined with immunohistochemistry revealed that 87.5% of labelled neurons in the pelvic plexus were NPY-immunoreactive. Following injection of fluorogold into the upper part of the uterus, 92% of labelled neurons in the suprarenal ganglia were NPY-immunoreactive. Treatment with 6-hydroxydopamine revealed that the NPY-immunoreactive nerve fibres were non-noradrenergic in the cervix, but were noradrenergic in the upper part of the uterus. In the uterine body and lower part of the uterine horn, both noradrenergic and non-noradrenergic NPY-immunoreactive nerve fibres were observed. These data demonstrate the major contribution of pelvic plexus neurons in the non-noradrenergic NPY innervation of the lower part of the genital tract, and the involvement of the suprarenal ganglia in the noradrenergic NPY innervation of the upper part of the uterus via the ovarian nerve plexus.

Ultrastructural changes in the nerve fiber population of anastomosed vagal and spinal accessory nerves in the sheep

The ultrastructure of the vagal and spinal accessory nerves was studied 1) in normal sheep and 2) in sheep in which an experimental crossed‐nerve anastomosis had been made by sectioning the supranodose vagal and spinal accessory nerves, then suturing the distal end of the vagal nerve to the distal end of the spinal accessory nerve, and allowing time for regeneration to occur. This study was carried out in order to analyze the modifications liable to occur when this technique is used and to specify the origin and the nature of the fibers that colonize the spinal accessory nerve.