Anatomical evidence for two spinal 'afferent-interneuron-efferent' reflex pathways involved in micturition in the rat: a 'pelvic nerve' reflex pathway and a 'sacrolumbar intersegmental' reflex pathway

We labeled interneurons in the L1-L2 and L6-S1 spinal cord segments of the rat that are involved in bladder innervation using transneuronal retrograde transport of pseudorabies virus (PRV) in normal animals and in animals with selected nerve transections. Preganglionic neurons were identified using antisera against choline acetyltransferase (ChAT). In some experiments we labelled parasympathetic preganglionic neurons (PPNs) in the L6-S1 spinal cord by retrograde transport of Fluorogold from the major pelvic ganglion. We identified bladder afferent terminals using the transganglionic transport of the anterograde tracer cholera toxin subunit b. We present anatomical evidence for two spinal pathways involved in innervation of the bladder. First, in the intact rat, afferent information from the bladder connects, via interneurons in L6-S1, to the PPNs that provide the efferent innervation of the bladder. The afferent terminals were located mainly in close apposition to interneurons located dorsal to the retrogradely labeled PPNs. Second, using L6-S1 ganglionectomies or L6-S1 ventral root rhizotomies we limited viral transport to the sympathetic pathways innervating the bladder. This procedure also labelled interneurons (but not PPNs) with PRV in the L6-S1 spinal cord in a location very similar to those described in the intact rat. These interneurons also receive bladder afferent terminals but we propose that they project to sympathetic preganglionic neurons, most of which are in the L1-L2 spinal segments. Based on this anatomical evidence, we propose the existence of two spinal reflex pathways involved in micturition: a pathway limited to a reflex arc in the pelvic nerve (presumably excitatory to the detrusor muscle); and a pathway involving the pelvic nerve and sympathetic nerve fibers, some of which may travel in the hypogastric (presumably inhibitory to the detrusor muscle).     

Anatomical evidence for two spinal ‘afferent–interneuron–efferent’ reflex pathways involved in micturition in the rat: a ‘pelvic nerve’ reflex pathway and a ‘sacrolumbar intersegmental’ reflex pathway

We labeled interneurons in the L1–L2 and L6–S1 spinal cord segments of the rat that are involved in bladder innervation using transneuronal retrograde transport of pseudorabies virus (PRV) in normal animals and in animals with selected nerve transections. Preganglionic neurons were identified using antisera against choline acetyltransferase (ChAT). In some experiments we labelled parasympathetic preganglionic neurons (PPNs) in the L6–S1 spinal cord by retrograde transport of Fluorogold from the major pelvic ganglion. We identified bladder afferent terminals using the transganglionic transport of the anterograde tracer cholera toxin subunit b. We present anatomical evidence for two spinal pathways involved in innervation of the bladder. First, in the intact rat, afferent information from the bladder connects, via interneurons in L6–S1, to the PPNs that provide the efferent innervation of the bladder. The afferent terminals were located mainly in close apposition to interneurons located dorsal to the retrogradely labeled PPNs. Second, using L6–S1 ganglionectomies or L6–S1 ventral root rhizotomies we limited viral transport to the sympathetic pathways innervating the bladder. This procedure also labelled interneurons (but not PPNs) with PRV in the L6–S1 spinal cord in a location very similar to those described in the intact rat. These interneurons also receive bladder afferent terminals but we propose that they project to sympathetic preganglionic neurons, most of which are in the L1–L2 spinal segments. Based on this anatomical evidence, we propose the existence of two spinal reflex pathways involved in micturition: a pathway limited to a reflex arc in the pelvic nerve (presumably excitatory to the detrusor muscle); and a pathway involving the pelvic nerve and sympathetic nerve fibers, some of which may travel in the hypogastric (presumably inhibitory to the detrusor muscle).     

Distribution of NADPH-d and nNOS-IR in the thoracolumbar and sacrococcygeal spinal cord of the guinea pig

The distribution of NADPH-d staining and neuronal nitric oxide synthase (nNOS)-immunoreactivity in the spinal cord of the guinea pig was studied to evaluate the potential role of nitric oxide in lumbosacral afferent and spinal autonomic pathways and to compare the distribution of these two markers to that observed in other species. NADPH-d staining and nNOS-immunoreactivity were present in neurons and fibers in the superficial dorsal horn, dorsal commissure and in neurons around the central canal in all levels of the spinal cord examined. Sympathetic preganglionic neurons in the thoracic and rostral lumbar segments identified by choline acetyl transferase (ChAT) immunoreactivity exhibited prominent NADPH-d staining and nNOS-immunoreactivity; whereas the ChAT-immunoreactive parasympathetic preganglionic neurons in the sacral segments were not stained. The most prominent NADPH-d staining in the sacral segments occurred in fibers extending from Lissauer's tract through laminae I along the lateral edge of the dorsal horn to the region of the sacral parasympathetic nucleus (lateral collateral pathway of Lissauer). These fibers were prominent in the S1-S3 segments but not in adjacent (L5-L7 and Cx1) or thoracolumbar segments. These NADPH-d fibers were, for the most part, not nNOS-immunoreactive, but did overlap with a prominent fiber bundle containing vasoactive intestinal polypeptide immunoreactivity in the sacral spinal cord. These results indicate that nitric oxide may function as a transmitter in thoracolumbar sympathetic preganglionic neurons, but not in sacral parasympathetic preganglionic neurons. Although the functional significance of the NADPH-d positive, nNOS-negative fiber bundle on the lateral edge of the sacral dorsal horn remains to be determined, this fiber tract may represent, in part, visceral afferent projections to the sacral parasympathetic nucleus.     

Spinal segmental sympathetic outflow to cervical sympathetic trunk, vertebral nerve, inferior cardiac nerve and sympathetic fibres in the thoracic vagus

The spinal segmental localization of preganglionic neurons which convey activity to the sympathetic nerves, i.e. vertebral nerve, right inferior cardiac nerve, sympathetic fibres in the thoracic vagus and cervical sympathetic trunk, was determined on the right side in chloralose anaesthetized cats. For that purpose the upper thoracic white rami were electrically stimulated with a single pulse, suprathreshold for B and C fibres, and the evoked responses were recorded in the sympathetic nerves. The relative preganglionic input from each segment of the spinal cord to the four sympathetic nerves was determined from the size of the evoked responses. It was found that each sympathetic nerve receives a maximum preganglionic input from one segment of the spinal cord (dominant segment) and that the preganglionic input gradually decreased from neighbouring segments. The spinal segmental preganglionic outflow to the cervical sympathetic trunk, thoracic vagus, right inferior cardiac nerve and vertebral nerve gradually shifted from the most rostral to the most caudal spinal cord segments. In some cases, a marked postganglionic component was found in the cervical sympathetic trunk. It was evoked by preganglionic input from the same spinal cord segments which transmitted activity to the vertebral nerve. These results indicate that there is a fixed relation between the spinal segmental localization of preganglionic neurons and the branch of the stellate ganglion receiving the input from these neurons.     

Hypothalamic paraventricular axons projecting to the female rat lumbosacral spinal cord contain oxytocin immunoreactivity

Oxytocin-containing axons project from the hypothalamic paraventricular nucleus to the neurohypophysis and thoracic spinal cord to ultimately influence uterine contractions and autonomic activity, respectively. Whether or not oxytocin-immunoreactive axons project to the female rat lumbosacral spinal cord to influence autonomic outflow to pelvic organs has not been investigated. Thus, the present study was designed to investigate the presence, distribution, and origin of oxytocin-immunoreactive axons in the female rat lumbosacral spinal cord. Immunohistochemistry, spinal cord transections, and axonal tracing with Fluorogold, True Blue, and pseudorabies virus were used. Oxytocin-immunoreactive nerve fibers were present in the L6/S1 segments of the spinal cord. Prominent varicose axons were evident throughout the dorsal horn, along the lateral and medial collateral pathways, in the dorsal intermediate gray area, around the central canal in lamina X, and throughout the sacral parasympathetic nucleus. Injection of retrograde tracer into the L6/S1 spinal cord labeled neurons in the hypothalamic paraventricular nucleus. Transection of the thoracic spinal cord eliminated oxytocin-immunoreactive nerve axons in the L6/S1 spinal cord. In addition, transection of the thoracic spinal cord eliminated transport of retrograde axonal tracer from the L6/S1 spinal cord to the paraventricular nucleus. Pseudorabies virus, a transneuronal retrograde tracer, injected into the uterus and cervix marked uterine-related preganglionic neuronal cell bodies in the sacral parasympathetic nucleus and uterine-related neurons in the hypothalamic paraventricular nucleus. Double immuno-labeling of viral-infected spinal cord sections showed oxytocin-immunoreactive axons closely associated with viral labeled uterine-related preganglionic cell bodies of the sacral parasympathetic nucleus. The results of this study revealed that oxytocin-immunoreactive neurons of the hypothalamic paraventricular nucleus project axons to the lumbosacral spinal cord to areas involved in sensory processing and parasympathetic outflow to the uterus.     

Identification of preganglionic parasympathetic neruons in the sacral spinal cord of the cat

The preganglionic parasympathetic neurons in the sacral spinal cord of the cat have been demonstrated by retrogade changes following section of the pelvic nerve. Transection of the pelvic nerve twice, a week apart, was necessary to produce reliable signs of chromatolysis in the preganglionic neurons. Serial sections of the sacral spinal cord were made and the location of affected cells plotted. The sacral parasympathetic nucleus was located in the intermediate region of S-2 and S-3. The majority of the perikarya were located in the intermediolateral cell column, but a significant number were also found in the intermediomedial column. The distribution of afferent fibers in the pelvic nerve was demonstrated by chromatolysis in cells of the dorsal root ganglia. Retrograde changes were limited to the ganglia of S-2 and S-3 in five cats, while a few cells with chromatolysis were found also in the S-1 ganglion of four cats.     

Distinct localization and target specificity of galanin-immunoreactive sympathetic preganglionic neurons of a teleost, the filefish Stephanolepis cirrhifer

Immunoreactivity for galanin was examined in the sympathetic preganglionic neurons in the spinal cord, adrenal glands, sympathetic ganglia, and some sensory ganglia of the filefish Stephanolepis cirrhifer. Galanin-immunoreactive neurons were found only in the rostral part, but not in the caudal part of the central autonomic nucleus (a column of sympathetic preganglionic neurons of teleosts). Many galanin-immunoreactive nerve terminals were found in contact with neurons in the celiac ganglia and the cranial sympathetic ganglia on both sides of the body. Most neurons encircled by galanin-immunoreactive nerve fibers were negative for tyrosine hydroxylase. Galanin-immunoreactive nerve fibers were very sparse in the spinal sympathetic paravertebral ganglia. No galanin-immunoreactive nerve fibers were found in the adrenal glands. No sensory neurons of the trigeminal, vagal, or spinal dorsal root ganglia were positive for galanin-immunoreactivity. These results suggest that galanin-immunoreactive sympathetic preganglionic neurons have distinct segmental localization and might project specifically to a population of non-adrenergic sympathetic postganglionic neurons in the celiac and cranial sympathetic ganglia.     

Galanin-like immunoreactivity in autonomic regions of the rat lumbosacral spinal cord is sexually dimorphic and varies with the estrous cycle.

These investigations show that there is a heterogeneous distribution of galanin-like immunoreactivity (GAL-LI) within laminae VII and X of the rat thoraco-sacral spinal cord. In either sex, GAL-LI fibers sparsely outline the position of male and female preganglionic sympathetic neurons in thoracic spinal segments; whereas in lumbosacral segments, far greater numbers of GAL-LI fibers surround autonomic preganglionic neurons. An unusual feature of the GAL-LI fibers in lumbosacral autonomic regions is their sexually dimorphic distribution with males containing greater numbers of GAL-LI fibers than all females examined. In this regard, although the number of GAL-LI fibers observed in males was consistent from animal to animal, the amount of GAL-LI in females fell into two qualitative categories: an 'average' and a 'heavy' amount. These data indicate that the difference in the amount of GAL-LI in the female rat lumbosacral spinal cord is related to the estrous cycle, such that heavy amounts of GAL-LI are observed during proestrus and estrus, while average amounts of GAL-LI are associated with metestrus and diestrus.     

Localization of NADPH diaphorase in the lumbosacral spinal cord and dorsal root ganglia of the cat

The distribution of NADPH-d activity in the spinal cord and dorsal root ganglia of the cat was studied to evaluate the role of nitric oxide in lumbosacral afferent and spinal autonomic pathways. At all levels of the spinal cord NADPH-d staining was present in neurons and fibers in the superficial dorsal horn and in neurons around the central canal and in the dorsal commissure. In addition, the sympathetic autonomic nucleus in the rostral lumbar segments exhibited prominent NADPH-d cellular staining whereas the parasympathetic nucleus in the sacral segments was not well stained. The most prominent NADPH-d activity in the sacral segments occurred in fibers extending from Lissauer's tract through laminae I along the lateral edge of the dorsal horn to lamina V and the region of the sacral parasympathetic nucleus. These fibers were very similar to VIP-containing and pelvic nerve afferent projections in the same region. They were prominent in the S₁–S₃ segments but not in adjacent segments (L₆–L₇ and Cx₁) or in thoracolumbar and cervical segments. NADPH-d activity and VIP immunoreactivity in Lissauer's tract and the lateral dorsal horn were eliminated or greatly reduced after dorsal-ventral rhizotomy (S₁–S₃), indicating the fibers represent primary afferent projections. A population of small diameter afferent neurons in the L₇–S₂ dorsal root ganglia were intensely stained for NADPH-d. The functional significance of the NADPH-d histochemical stain remains to be determined; however, if NADPH-d is nitric oxide synthase then this would suggest that nitric oxide may function as a transmitter in thoracolumbar sympathetic preganglionic efferent pathways and in sacral parasympathetic afferent pathways in the cat. © 1994 Wiley-Liss, Inc.     

The Role of Vasoactive Intestinal Polypeptide and Pituitary Adenylate Cyclase-Activating Polypeptide in the Neural Pathways Controlling the Lower Urinary Tract

Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are expressed in the neural pathways regulating the lower urinary tract. VIP-immunoreactivity (IR) is present in afferent and autonomic efferent neurons innervating the bladder and urethra, whereas PACAP-IR is present primarily in afferent neurons. Exogenously applied VIP relaxes bladder and urethral smooth muscle and excites parasympathetic neurons in bladder ganglia. PACAP relaxes bladder and urethral smooth muscle in some species (pig) but excites the smooth muscle in other species (mouse). Intrathecal administration of VIP in cats with an intact spinal cord suppresses reflex bladder activity, but intrathecal administration of VIP or PACAP in rats enhances bladder activity and suppresses urethral sphincter activity. PACAP has presynaptic facilitatory effects and direct excitatory effects on lumbosacral parasympathetic preganglionic neurons. Chronic spinal cord transection produces an expansion of VIP-IR (cats) and PACAP-IR (rats) in primary afferent axons in the lumbosacral spinal cord and unmasks spinal excitatory effects of VIP on bladder reflexes in cats. Intrathecal administration of PACAP6-38, a PAC1 receptor antagonist, reduces bladder hyperactivity in chronic spinal-cord-injured rats. These observations raise the possibility that VIP or PACAP have a role in the control of normal or abnormal voiding.     

Response properties of neurons of the lateral cervical nucleus in the rat.

The distribution in the spinal cord of the rat of preganglionic neurons sending fibers into the hypogastric nerve was determined with the retrograde transport of horseradish peroxidase (HRP). Labeled cells were present in the intermediate gray matter of spinal segments L₁-L₂. The majority (81%) of HRP-filled cells formed a continuous column along the midline in the dorsal gray commissure. This cell column was termed the dorsal commissural nucleus (DCN). The remainder of HRP-labeled cells were present bilaterally in the middle and lateral regions of the intermediate gray; the majority of the latter cells were located along the lateral border of the intermediate gray. The present finding of a midline preganglionic autonomic cell column in the spinal cord of a mammal is contrary to previous reports, in which sympathetic preganglionic neurons have been localized primarily in the lateral intermediate gray. The DCN may be species-specific and related to the system of short adrenergic neurons present in the pelvis.     

Some observations on the catecholaminergic innervation of the intermediate zone of the thoracolumbar spinal cord of the cat

The anatomical arrangement of catecholaminergic nerve terminals in the intermediate zone of the thoracolumbar spinal cord was examined with the fluorescence microscope in serial sections of spinal cord from adult cats perfused with a formaldehyde-glutaraldehyde mixture. Specific fluorescence in this material was assumed to represent noradrenaline. The distribution of fluorescent varicose nerve terminals was compared with that of neuron cell bodies in the same sections after Nissl counterstaining, and with the known topographic distribution of sympathetic preganglionic neurons. Dense accumulations of noradrenergic fibers were found in the intermediate zone in all segments between the caudal part of C8 and the rostral part of L4. These were not only associated with preganglionic neurons in the intermediolateral columns (ILN), but below T5 also extended in bands (1-3 per mmm of spinal cord) toward, and in some segments across, the midline. Noradrenergic terminals were associated with cell bodies in most parts of the ILN from T1 to T8 and in L2-3. Between T9 and L2, the innervation of the ILN was patchy, and the majority of the noradrenergic fibers projected to regions medial to the ILN. These corresponded to sites at which preganglionic neurons and also possible interneurons of the intermediomedial nucleus occur. Although preganglionic neurons and clusters of noradrenergic terminals are located in similar regions across the intermediate zone, their densities and patterns of distribution differ. This observation applies to comparisons both between anatomical subnuclei and between segments in a characteristic way along the length of the thoracolumbar cord.     

Ontogeny of adrenergic fibers in rat spinal cord in relationship to adrenal preganglionic neurons

Adrenergic neurons in the C1 cell group in the rostral ventrolateral medulla oblongata contain epinephrine, as well as its biosynthetic enzyme, phenylethanolamine N-methyltransferase (PNMT). These neurons send axons to regions of the central nervous system known to regulate autonomic function, including the sympathetic preganglionic nuclei of thoracic and upper lumbar spinal cord. Previous studies have shown that PNMT is expressed in neurons located in the medulla oblongata on embryonic day 14; however, the development of the projections from these cells has not been studied. With the aid of high-performance liquid chromatography (HPLC) to determine levels of catecholamines and immunocytochemistry to demonstrate PNMT, the ontogeny of the adrenergic bulbospinal pathway in the embryonic, postnatal, and adult rat has been studied. In addition, the relationship between PNMT-immunoreactive (IR) fibers and retrogradely labeled sympathetic preganglionic neurons projecting to adrenal medulla are described. PNMT-IR fibers were first observed in the caudal medulla oblongata and lateral funiculus of spinal cord on gestational day 15(E15). On E16, PNMT-IR fibers in the thoracic spinal cord were observed in the intermediate gray matter at the level of the lateral horn. Epinephrine was measureable in spinal cord on E20. Both the density of PNMT-IR fibers and the levels of epinephrine increased to a maximum during the second postnatal week and then declined to adult levels. These observations suggest that a period of adrenergic hyperinnervation of spinal sympathetic nuclei occurs during the neonatal period. PNMT-IR terminals in spinal cord were observed, primarily, although not exclusively, in sympathetic nuclei of thoracic cord and parasympathetic nuclei of upper sacral cord. Adrenergic fibers in the intermediolateral nucleus (IML) and the central autonomic nucleus (CAN) dorsal to the central canal were particularly dense during the second postnatal week in both midthoracic and upper sacral segments. In the neonate, a "ladder-like" pattern of PNMT-IR fiber staining was observed which represented transverse fiber bundles connecting IML with CAN and extensive longitundinal fiber bundles along the border of the funiculus in IML. At all spinal levels, adrenergic fibers were also observed adjacent to the ependyma dorsal or lateral to the central canal. The relationship between adrenal preganglionic neurons and PNMT-IR fibers in IML was examined on postnatal days 4, 15, and 60. With retrograde labeling from adrenal medulla, it was demonstrated that PNMT-IR fibers are associated with adrenal preganglionic neurons throughout postnatal development.(ABSTRACT TRUNCATED AT 400 WORDS)     

Changes in galanin immunoreactivity in rat lumbosacral spinal cord and dorsal root ganglia after spinal cord injury

Alterations in the expression of the neuropeptide galanin were examined in micturition reflex pathways 6 weeks after complete spinal cord transection (T8). In control animals, galanin expression was present in specific regions of the gray matter in the rostral lumbar and caudal lumbosacral spinal cord, including: (1) the dorsal commissure; (2) the superficial dorsal horn; (3) the regions of the intermediolateral cell column (L1-L2) and the sacral parasympathetic nucleus (L6-S1); and (4) the lateral collateral pathway in lumbosacral spinal segments. Densitometry analysis demonstrated significant increases (P < or = 0.001) in galanin immunoreactivity (IR) in these regions of the S1 spinal cord after spinal cord injury (SCI). Changes in galanin-IR were not observed at the L4-L6 segments except for an increase in galanin-IR in the dorsal commissure in the L4 segment. In contrast, decreases in galanin-IR were observed in the L1 segment. The number of galanin-IR cells increased (P < or = 0.001) in the L1 and S1 dorsal root ganglia (DRG) after SCI. In all DRG examined (L1, L2, L6, and S1), the percentage of bladder afferent cells expressing galanin-IR significantly increased (4-19-fold) after chronic SCI. In contrast, galanin expression in nerve fibers in the urinary bladder detrusor and urothelium was decreased or eliminated after SCI. Expression of the neurotrophic factors nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) was altered in the spinal cord after SCI. A significant increase in BDNF expression was present in spinal cord segments after SCI. In contrast, NGF expression was only increased in the spinal segments adjacent and rostral to the transection site (T7-T8), whereas spinal segments (T13-L1; L6-S1), distal to the transection site exhibited decreased NGF expression. Changes in galanin expression in micturition pathways after SCI may be mediated by changing neurotrophic factor expression, particularly BDNF. These changes may contribute to urinary bladder dysfunction after SCI.     

Increased c-fos expression in spinal neurons after irritation of the lower urinary tract in the rat.

This study utilized neuronal c-fos expression to examine the spinal pathways involved in processing nociceptive and non-nociceptive afferent input from the lower urinary tract (LUT) of the urethane-anesthetized rat. C-fos protein was detected immunocytochemically in only a small number of cells (< 2 cells/L6 section) in control animals. However, chemical irritation with 1% acetic acid or mechanical stimulation of the LUT markedly increased the number of c-fos-positive neurons (56-180 cells/L6 section) in four regions of the caudal lumbosacral (L6-S1) spinal cord: medial dorsal horn (MDH), lateral dorsal horn, dorsal commissure (DCM), and sacral parasympathetic nucleus (SPN). Only small numbers of c-fos-positive cells were detected in rostral lumbar segments, a region that is thought to receive nociceptive input from the LUT via afferent pathways in sympathetic nerves. The distribution of c-fos-positive cells in the L6 spinal cord varied according to the stimulus (i.e., urethral catheter, bladder distension, or chemical irritation). Distension of the urinary bladder increased the number of c-fos-positive cells mainly in DCM and SPN regions of the cord. In contrast, irritation of the LUT increased c-fos expression largely in DCM and MDH areas. Spinal cord transection (T8 level) did not alter the c-fos expression induced by a catheter or chemical irritation, indicating that gene expression was mediated by spinal pathways. Denervation experiments showed that c-fos expression was induced by activation of afferent pathways in the pelvic and pudendal nerves. These results suggest that neurons in several regions of the spinal cord are involved in processing afferent input from different parts of the LUT. Neurons in the DCM appear to have an important role since they respond to both nociceptive and non-nociceptive inputs and to visceral (pelvic nerve) and somatic (pudendal nerve) afferent pathways. Thus, these neurons may be involved in the mechanisms of visceral-somatic referred pain.     

Spinal origins of preganglionic B and C neurons that innervate paravertebral sympathetic ganglia nine and ten of the bullfrog

These experiments were designed to characterize the distribution, morphology, and number of spinal preganglionic neurons that selectively innervate the B- and C-type sympathetic neurons in paravertebral ganglia 9 and 10 of the bullfrog. For this purpose, horseradish peroxidase (HRP) was applied to the anterior end of the sectioned sympathetic chain between ganglia 8 and 9. Subsequent retrograde axonal transport of the HRP labeled ipsilateral spinal neurons whose cell bodies form a column having rostral and caudal boundaries that are, respectively, just caudal to the level of spinal nerve 4 and midway between the entry zones of spinal nerves 7 and 8. In all segments, the labeled preganglionic somata were found in the lateral half of the spinal gray and slightly dorsal to the central canal; a position analogous to that of the intermediolateral cell column in mammals. Most labeled preganglionic neurons were multipolar in shape, and the cell bodies lying between spinal nerves 4 and 5 were, on average, larger than those found between spinal nerves 7 and 8. In transverse sections that were cut near spinal nerve 5, the axons of preganglionic neurons could be seen to exit the cord through ventral roots. Counts of labeled preganglionic neurons indicate that an average +/- S.D. of 338 +/- 89 cells innervate ganglia 9 and 10. Selective labeling of preganglionic B neurons, by cutting spinal nerves 7 and 8 central to their rami communicantes at the time of HRP application, revealed an average +/- S.D. of 137 +/- 31 cells that lie exclusively between spinal nerves 4 and 6. By contrast, selective labeling of preganglionic C neurons, by cutting the sympathetic chain rostral to ganglion 7 at the time of HRP application, revealed an average +/- S.D. of 187 +/- 77 cells in an adjacent portion of the preganglionic column that is bounded by spinal nerve 6 and by a point midway between spinal nerves 7 and 8. These results thus demonstrate a clear segmental segregation between the preganglionic B and C neurons that innervate ganglia 9 and 10.     

An immunohistochemical study of methionine-enkephalin-Arg6-Gly7-Leu8-like immunoreactivity-containing neurons in the parasympathetic preganglionic regions of the rat spinal cord

The localization of the methionine-enkephalin-Arg6-Gly7-Leu8 (Met-Enk-Arg-Gly-Leu)-like immunoreactivity-containing neurons in the rat lumbosacral spinal cord was immunohistochemically examined by an antiserum very specific to Met-Enk-Arg-Gly-Leu. The immunoreactive neurons occupied the positions corresponding to the parasympathetic preganglionic nuclei determined by the previous horseradish peroxidase (HRP)-tracing experiments. The present study suggests that the parasympathetic preganglionic neurons in the rat lumbosacral spinal cord produce preproenkephalin A and its related peptides.     

Acute autonomic and sensory neuropathy: report of an autopsy case

Summary A 46-year-old woman presented acute sensori-motor neuropathy of the Guillain-Barré type, followed by a protracted course of profound autonomic and sensory dysfunction. Tests of autonomic functions showed denervation hypersensitivity. Neuropathologically, the trigeminal sensory nuclei, solitary nucleus, the dorsal columns of the spinal cord and dorsal spinal roots showed severe degeneration. Degeneration was found both in the preganglionic (intermediolateral cell columns of the spinal cord) and postganglionic (sympathetic ganglion and celiac ganglion) neurons of the sympathetic nervous system, and the preganglionic (dorsal motor nucleus of the vagus) and postganglionic (Auerbach's plexus) neurons of the parasympathetic nervous system.     

An immunohistochemical study of methionine-enkephalin-Arg-Gly-Leu-like immunoreactivity-containing neurons in the parasympathetic preganglionic regions of the rat spinal cord

The localization of the methionine-enkephalin-Arg⁶-Gly⁷-Leu⁸ (Met-Enk-Arg-Gly-Leu)-like immunoreactivity-containing neurons in the rat lumbosacral spinal cord was immunohistochemically examined by an antiserum very specific to Met-Enk-Arg-Gly-Leu. The immunoreactive neurons occupied the positions corresponding to the parasympathetic preganglionic nuclei determined by the previous horseradish peroxidase (HRP)-tracing experiments. The present study suggests that the parasympathetic preganglionic neurons in the rat lumbosacral spinal cord produce preproenkephalin A and its related peptides.     

Selective plasticity of primary afferent innervation to the dorsal horn and autonomic nuclei following lumbosacral ventral root avulsion and reimplantation in long term studies

Previous studies involving injuries to the nerves of the cauda equina and the conus medullaris have shown that lumbosacral ventral root avulsion in rat models results in denervation and dysfunction of the lower urinary tract, retrograde and progressive cell death of the axotomized motor and parasympathetic neurons, as well as the emergence of neuropathic pain. Root reimplantation has also been shown to ameliorate several of these responses, but experiments thus far have been limited to studying the effects of lesion and reimplantation local to the lumbosacral region. Here, we have expanded the region of investigation after lumbosacral ventral root avulsion and reimplantation to include the thoracolumbar sympathetic region of the spinal cord. Using a retrograde tracer injected into the major pelvic ganglion, we were able to define the levels of the spinal cord that contain sympathetic preganglionic neurons innervating the lower urinary tract. We have conducted studies on the effects of the lumbosacral ventral root avulsion and reimplantation models on the afferent innervation of the dorsal horn and autonomic nuclei at both thoracolumbar and lumbosacral levels through immunohistochemistry for the markers calcitonin gene-related peptide (CGRP) and vesicular glutamate transporter 1 (VGLUT1). Surprisingly, our experiments reveal a selective and significant decrease of CGRP-positive innervation in the dorsal horn at thoracolumbar levels that is partially restored with root reimplantation. However, no similar changes were detected at the lumbosacral levels despite the injury and repair targeting efferent neurons, and being performed at the lumbosacral levels. Despite the changes evident in the thoracolumbar dorsal horn, we find no changes in afferent innervation of the autonomic nuclei at either sympathetic or parasympathetic segmental levels by CGRP or VGLUT1. We conclude that even remote, efferent root injuries and repair procedures can have an effect on remote and non-lesioned sensory systems sharing common peripheral ganglia.