Anatomical and physiological properties of pelvic ganglion neurons in female mice.

Most neurons that regulate motility and blood flow in female pelvic organs are located within pelvic (paracervical) ganglia. In this study we investigated the anatomical and physiological properties of neurons within mouse (C57/Bl/6) paracervical ganglia. Most neurons showed immunoreactivity for choline acetyl transferase (CHAT) and were presumably cholinergic. Few neurons (approximately 5%) were tyrosine hydroxylase (TH) positive. Immunohistochemical labelling for microtubule associated protein 2 showed most neurons had small somata (cross sectional area approximately 300 microm(2)) and lacked dendrites. Action potential (AP) discharge characteristics, determined by depolarising current step injection, revealed most neurons (70%) adapted rapidly to depolarising current injection and were classified as "phasic". The remaining neurons discharged APs throughout the current step and were classified as "tonic". Membrane properties and current-voltage relationships were similar in phasic and tonic neurons, however the afterhyperpolarisation was significantly smaller in tonic neurons. Stimulation of preganglionic axons usually evoked a single strong preganglionic input (21/27 and 9/10 for pelvic and hypogastric nerves, respectively). In 19 preparations where we tested for inputs from both nerves pelvic inputs predominated (23/45 neurons) and inputs via the hypogastric nerve were rarely observed (3/45 neurons). Together, our data indicate that most neurons within mouse paracervical ganglia are cholinergic and parasympathetic. As there is little anatomical or functional evidence for integration of preganglionic inputs we propose that the role of paracervical neurons is restricted to one of spatial amplification or filtering of preganglionic inputs.

The same dorsal root ganglion neurons innervate uterus and colon in the rat.

The purpose of this study was to determine whether primary sensory neurons that innervate the uterus receive convergent input from the colon. To test this, in the rat, cell bodies of colonic and uterine dorsal root ganglia were retrogradely labeled with fluorescent tracer dyes microinjected into the colon/rectum and bilaterally into the uterine horns. Ganglia were harvested, cryoprotected and cut into 20 microm slices to identify positively stained cells for fluorescent microscopy. Up to 5% of neurons were colon-specific or uterus-specific, and 10-15% of labeled ganglion neurons innervate both viscera in the L1, L2, L6 and S1-S3 levels. These results suggest a novel form of visceral sensory integration in the dorsal root ganglion that may underlie comorbidity of many functional pain syndromes.

Estrogen receptors in the spinal cord, sensory ganglia, and pelvic autonomic ganglia.

Until relatively recently, most studies of the effects of estradiol in the nervous system focused on hypothalamic, limbic, and other brain centers involved in reproductive hormone output, feedback, and behaviors. Almost no studies addressed estradiol effects at the spinal cord or peripheral nervous system level. Prior to the mid-1960s-1970s, few studies examined neural components of reproductive endocrine organs (e.g., ovary or testis) or the genital organs (e.g., uterus or penis) because available data supported endocrine regulation of these structures. Over the last two decades interest in and studies on the innervation of the genital organs have burgeoned. Because of the responsiveness of genital organs to sex steroid hormones, these neural studies seeded interest in whether or not autonomic and sensory neurons that innervate these organs, along with their attendant spinal cord circuits, also are responsive to sex hormones. From the mid-1980s there has been a steady growth of interest in, and studies of the neuroanatomy, neurochemistry, neural connectivity, and neural functional aspects in reproductive organs and the response of these parameters to sex steroids. Thus, with the growth of probes and techniques, has come studies of anatomy, neurochemistry, and circuitry of sex hormone-responsive neurons and circuits in the spinal cord and peripheral nervous system. This review focuses on estrogen receptors in sensory, autonomic, and spinal cord neurons in locales that are associated with innervation of female reproductive organs.

Androgens modulate nitric oxide synthase messenger ribonucleic acid expression in neurons of the major pelvic ganglion in the rat.

Expression and androgen regulation of the gene for neuronal nitric oxide synthase (NOS I) were examined in neurons of the major pelvic ganglia in male rats. Some of these postganglionic neurons innervate the penis and produce nitric oxide, which is believed to play a major role in penile erection. Rats were either castrated or sham operated and implanted with SILASTIC brand capsules filled with powdered testosterone (T) or 5alpha-dihydrotestosterone (5alphaDHT) or left empty. After 4 days, the number of neurons intensely stained for NADPH-diaphorase as well as those giving a NOS I signal in in situ hybridization experiments increased in castrated rats treated with testosterone by 31% and 42%, respectively, relative to those in untreated castrated rats. This suggests that the increase in NADPH-diaphorase activity resulted from enzyme synthesis and was due to a modification of NOS I messenger RNA (mRNA) accumulation. After 7 days, Northern blot analysis showed that castration produced a decrease in the amount of NOS I mRNA relative to that of ribosomal RNA. This decrease was almost prevented by T treatment. No significant differences were observed by reverse transcriptase-PCR between 7-day and 28-day treatments. However, in 7-day castrated rats treated with 5alphaDHT, NOS I signals relative to those of hypoxanthine phosphoribosyltransferase, taken as reference, were significantly higher than those in castrated rats and resembled those in sham-castrated rats, suggesting that 5alphaDHT was probably more potent than testosterone in preventing the decrease in NOS I mRNA levels elicited by castration. These results show that NOS I can be positively regulated by androgens and are consistent with the suggestion that these steroids play a role in the physiological processes of penile erection.

The afferent and sympathetic components of the lumbar spinal outflow to the colon and pelvic organs in the cat. I. The hypogastric nerve.

The cell bodies of the lumbar sensory and sympathetic pre- and postganglionic neurons that project to the pelvic organs in the hypogastric nerve of the cat have been labeled retrogradely with horseradish peroxidase applied to the central end of their cut axons. The numbers, segmental distribution, location, and size of these labeled somata have been determined quantitatively. Afferent and preganglionic cell bodies were located bilaterally in dorsal root ganglia and spinal cord segments L3-L5, with the maximum numbers in L4. Very few cells lay rostral to L3. Afferent cell bodies were generally very small in cross-sectional area relative to the entire population in the dorsal root ganglia. Most of the preganglionic cell bodies lay clustered just medial to the region of the intermediolateral column and extended caudally well beyond its usual limit in the upper part of L4. These neurons were, on the average, larger than the cells of the intermediolateral column itself, with the largest cells lying in the most medial positions. Most of the post-ganglionic somata were in the ipsilateral distal lobe of the inferior mesenteric ganglion, while some (usually less than 10%) lay in accessory ganglia along the lumbar splanchnic nerves and in paravertebral ganglia L3-L5. Postganglionic somata in the inferior mesenteric ganglion were larger than both labeled and unlabeled ganglion cells in the paravertebral ganglia. From the data, it is estimated that about 1,300 afferent neurons, about 1,700 preganglionic neurons, and about 17,000 postganglionic neurons project in each hypogastric nerve in the cat.

Sexual dimorphism in sympathetic preganglionic neurons of the rat hypogastric nerve.

Horseradish peroxidase (HRP) applied to one hypogastric nerve labelled sensory neurons in T11-L3 dorsal root ganglia (DRG) bilaterally and preganglionic neurons (PGN) in the spinal cord segments T13-L3. An average of 130 small DRG neurons were labelled per animal (male or female). These were concentrated in the L1 + L2 DRGs (92%). About 75% were located ipsilateral to the site of HRP application. Central projections from DRG neurons were noted throughout Lissauer's tract and in the marginal zones (medial and lateral) near the borders of Lissauer's tract. A short projection was also seen extending to the dorsolateral funiculus. More than 90% of the preganglionic neurons were located in segments L1 + L2. Most of these were found in the dorsal commissural nucleus (75%) and most of the remainder were located bilaterally in the intermediolateral columns. Somewhat more intermediolateral neurons were labelled on the ipsilateral side than on the contralateral side. There were a few intercalating neurons and a very few funicular cells. An average of 415 PGNs were labelled in the male animals and 110 in the females, demonstrating a strong sexual dimorphism. No dimorphism was found in the sensory components.

The afferent and sympathetic components of the lumbar spinal outflow to the colon and pelvic organs in the cat. III. The colonic nerves, incorporating an analysis of all components of the lumbar prevertebral outflow.

The cell bodies of the lumbar sensory and sympathetic pre- and postganglionic neurons that project to the colon along the inferior mesenteric artery of the cat have been labeled retrogradely with horseradish peroxidase applied to the central end of their cut axons. The numbers, segmental distribution, location, and size of these labeled somata have been determined quantitatively. Afferent cell bodies were symmetrically distributed bilaterally in dorsal root ganglia T13-L5, with the maximum number (about 80%) in L3 and L4 and most of the rest in L2. Labeled afferent somata were small relative to the entire population of DRG cells. Occasionally a few preganglionic somata were labeled in the intermediate zone of L3 and L4 spinal cord segments. Postganglionic cell bodies were labeled bilaterally in the proximal lobes of the inferior mesenteric ganglion (70-95%), in accessory ganglia of the intermesenteric nerve and of the lumbar splanchnic nerves, and in lumbar paravertebral ganglia. The segmental distribution in the lumbar sympathetic trunk was symmetrical on both sides and was the same as that of the afferent cells. Labeled postganglionic cell bodies in both the IMG and the accessory ganglia were larger than labeled and unlabeled ganglion cells in the paravertebral ganglia. From these data, it is estimated that about 2,100 afferent neurons and about 29,000 postganglionic neurons project in the lumbar colonic nerves. In conjunction with equivalent data for the hypogastric and lumbar splanchnic nerves, the results provide a quantitative and spatial description of the afferent and efferent components of the lumbar innervation of the colon and pelvic viscera.

The spinal distribution of sympathetic preganglionic and visceral primary afferent neurons that send axons into the hypogastric nerves of the cat.

The spinal distribution of sympathetic preganglionic neurons (PGN) and visceral primary afferent neurons sending axons into the hypogastric nerve of the cat has been studied with HRP tracing techniques. After application of HRP to the cat hypogastric nerve, labeled PGN were identified in segments L2-L5. Most of these neurons were oriented transversely and were divided approximately equally between two nuclei: the principal nucleus and the intercalated nucleus. Cells were distributed in clusters at 160-361-microns intervals along the length of the cord. Sensory neurons were labeled in dorsal root ganglia from T12 to L5. Central axons of these visceral afferents were observed in the medial half of Lissauer's tract from T13 to L7. Afferent axon collaterals extended through lamina I on both sides of the dorsal horn but were most prominent on the lateral side, where they continued into lateral lamina V and VII, often overlapping the dorsal dendrites of PGN in this region. Labeled afferent projections exhibited a periodic distribution in lamina I with clusters of axons occurring at 235-343-microns intervals in the rostrocaudal axis. The central projection of hypogastric nerve primary afferents was qualitatively similar to the distribution of visceral afferent projections at other levels of the spinal cord.

Pseudorabies virus tracing of neural pathways between the uterine cervix and CNS: effects of survival time, estrogen treatment, rhizotomy, and pelvic nerve transection.

The transneuronal tracer, pseudorabies virus (PRV), was used to identify pathways from the uterine cervix which may be involved in induction of analgesia and abbreviation of estrus by vaginocervical stimulation. In Experiment I, PRV immunoreactivity (PRV-IR) in brain and spinal cord was examined 3-5 days after injection into the cervix of ovariectomized (OVX) female rats given estrogen (E) or control treatments. No differences in viral labeling were observed between OVX and OVX+E females at any time. PRV-infected cells were observed to increase as a function of time and at progressively higher CNS levels. PRV-IR neurons were first observed on day 3 post-infection at L6 in the SPN. Increased labeling was observed at day 4 in the SPN and the DGC at L6 and S1 spinal segments. Dorsal horn neurons showed PRV-IR by 4.5 days. Five days post-infection, labeling was seen in the IML and lamina X in T12-L1 segments, and in medullary raphe, A5, nPGi, nGi, DMV, lateral reticular, Barrington's nuclei, and in the midbrain PAG. In Experiment II, the effects of bilateral L6 dorsal root rhizotomy (RH) combined with unilateral (UPx) or bilateral (BPx) pelvic nerve transection on PRV infectivity were examined 5 days after infection. Despite reductions in substance P labeling in the dorsal horn following RH, PRV-IR neurons persisted in this area. In RH+UPx females, labeling persisted bilaterally in the SPN and DGC at L6. RH+BPx almost completely eliminated the PRV labeling in L6 and S1. Horizontal sections showed distinct patterns of infectivity within the IML of thoracolumbar and SPN of lumbosacral segments consistent with infection in the hypogastric and pelvic nerves, respectively. Our data indicate that retrograde transport of PRV occurs via the hypogastric and pelvic nerves after injection of the virus into the uterine cervix. Furthermore, significant intraspinal processing is likely to occur between thoracolumbar and lumbosacral levels in the modulation of reproductive tract function.

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.

The effects of iproniazid and reserpine on the accumulation of granular vesicles and noradrenaline in constricted adrenergic nerves.

1. The accumulation of granular vesicles proximal to a constriction applied to hypogastric nerves has been investigated with the electron microscope in cats treated with reserpine and/or iproniazid.2. The ultrastructural changes have been correlated with the accumulation of noradrenaline at the same site in similarly treated animals.3. The findings give further support to the view that granular vesicles constitute a major storage site for intraneuronal noradrenaline.

The pelvic plexus: innervation of pelvic and extrapelvic visceral tissues.

The pelvic plexus is an association of neurons that govern visceral tissues involved in eliminative and reproductive functions. It is the singular site in the autonomic nervous system where sympathetic and parasympathetic neurons occur in the same ganglia. Within the plexus, ganglia are not randomly positioned; sympathetic neurons tend to occur more ventrally while parasympathetic neurons are located more dorsally, both in accordance with the location of their target tissues and the entry point of their corresponding preganglionic nerve tracts. For example, the vas deferens and seminal vesicle are ventral in position and thus are innervated by more ventrally located pelvic neurons. Neurochemical studies of pelvic ganglia indicate that there are some characteristic associations of putative neurotransmitters which are based on target organ distribution and in part, dictated by the variety of target tissues within each organ. Penile neurons comprise a uniform population in that they are cholinergic and also may release vasoactive intestinal polypeptide (VIP) and nitric oxide. In contrast, target tissues of the internal genitalia are more diverse, requiring adrenergic and nonadrenergic innervation and a complementary neuropeptide. Preganglionic innervation may also be coded and although sympathetic and parasympathetic fibers are cholinergic, they may differ in respect to neuropeptides and nitric oxide. Sensory neuron collaterals may also influence principal neurons as do intrinsic neurons such as small intensely fluorescent cells. Transmission through pelvic ganglia may be simple as is apparent in penile innervation, or shows a greater integrative capacity, as exemplified by the innervation of the urinary bladder. The extent of interaction of sympathetic and parasympathetic pathways at the level of the pelvic plexus remains largely unknown.

Colocalization of vasoactive intestinal polypeptide and nitric oxide in penis-innervating neurons in the major pelvic ganglion of the rat.

By using a combination of fluorescent retrograde labeling and double immunofluorescence histochemistry, the present study revealed in the rat that the vast majority of major pelvic ganglion neurons innervating penile erectile tissue contained both vasoactive intestinal polypeptide (VIP) and nitric oxide synthase. The result suggests that VIP and nitric oxide may exert a cooperative action in penile erection.

A spinal cord slice preparation for analyzing synaptic responses to stimulation of pelvic and pudendal nerves in mature rats.

The dorsal commissural nucleus (DCN) in the lumbosacral spinal cord (L6-S1) receives primary afferent fibers from both pelvic and pudendal nerves in rats. However, the physiological and pharmacological properties of synaptic responses of the DCN neurons to stimulation of those nerves remain unclear. We have developed a longitudinal spinal cord (L6-S1) slice preparation from mature rats that retained both nerves attached. Blind whole-cell recordings were made from the DCN neurons in this preparation. In most neurons, mono- and/or poly-synaptic fast excitatory postsynaptic potentials (EPSPs) were evoked by electrical stimulation of either the pelvic or pudendal nerve. These EPSPs were mediated by activation of Abeta/Adelta and/or C fibers (conduction velocities, 0.5-17.3 m/s), and were abolished by CNQX. Fast EPSPs elicited by either pelvic or pudendal nerve stimulation were occasionally accompanied by bicuculline- and strychnine-sensitive IPSPs. In one-third of the neurons tested, mono- and/or poly-synaptic EPSPs were elicited by the stimulation of both the pelvic and pudendal nerves, indicating convergence of the visceral and somatic primary afferent inputs from the pelvic region onto the DCN neurons. The preparation is applicable to study the mechanism of the integration of the visceral and somatic inputs in the spinal cord.

Conduction velocity distribution of afferent fibers in the female rat hypogastric nerve.

Conduction velocities of single afferent fibers in the female rat hypogastric nerve were measured by stimulating dorsal rootlets and recording from the hypogastric nerve. A total of 344 units were identified and measured. They were distributed among dorsal roots T13 to L3 ipsilaterally (75%) and between L1 and L2 contralaterally (25%). Over 95% were found in the L1 plus L2 dorsal roots. Ninety-six percent of the units had conduction velocities less than 2 m/s; the average conduction velocity was 0.98 m/s. By way of contrast, afferents in the postganglionic nerves innervating the urinary bladder with conduction velocities less than 2 m/s constituted 65% of the afferents. We conclude that the overwhelming majority of afferents in the female rat hypogastric nerve are unmyelinated C-fibers.

Separate urinary bladder and external urethral sphincter neurons in the central nervous system of the rat: simultaneous labeling with two immunohistochemically distinguishable pseudorabies viruses.

This work examines the distribution, in the central nervous system, of virus-labeled neurons from the rat urinary bladder and the external urethral sphincter simultaneously within the same tissue sections. Two immunohistochemically distinct pseudorabies virus strains were injected into male Sprague--Dawley rats (approximately 280 g). One virus was injected into the bladder and the other into the external urethral sphincter. After incubation intervals of 2, 2.5 and 3 days, sections from the spinal cord and brain were treated immunohistochemically to detect cells which were labeled separately by each virus or were labeled by both viruses. The major result of these experiments is that each strain of virus labeled a separate population of neurons and that some neurons were labeled by both strains. In the lumbosacral cord, 3 days post-infection, neurons labeled by virus from the external urethral sphincter were found in Onuf's nucleus, the dorsal gray commissure, and the superficial dorsal horn. Neurons labeled by virus from the urinary bladder were found in the L6--S1 and L1--L2 spinal cord segments within the dorsal gray commissure, the intermediolateral area and the superficial dorsal horn. Double-labeled interneurons were mainly located in the dorsal gray commissure although some were also found in the intermediolateral area and the superficial dorsal horn. In the medulla, external urethral sphincter neurons and bladder neurons and double-labeled neurons were found in the reticular region and the raphe. More rostrally, bladder neurons were located in the pontine micturition center and external urethral sphincter neurons were found in the locus coeruleus and subcoeruleus. A very small number of double-labeled neurons were found in the pontine micturition center and the locus coeruleus or subcoeruleus.

Organizational role of testosterone on the biochemical and morphological development of the hypogastric ganglion.

Previous reports have demonstrated that after postnatal day 10 testosterone influences hypogastric ganglion (HG) development by 'activating' morphological and biochemical indices. We now report an 'organizational' influence on the developing HG during the first 10 postnatal days. To investigate the organizational effects of testosterone, male rats were castrated within 12 h of birth. Testosterone replacement therapy initiated following castration maintained the normal number of neurons in the HG. Conversely, delayed replacement therapy starting at day 10 or vehicle treatment only, resulted in a significant decrease in neuron number. Castration also produced a significant decrease in somal and nuclear cross-sectional areas. Testosterone replacement, whether initiated immediately or if delayed until day 10, restored somal and nuclear cross-sectional areas to normal. Tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) activities were sensitive to both testosterone dosage and the time of administration. Testosterone decanoate administered subsequent to castration was not able to completely reverse the enzyme activity deficits, while delayed replacement therapy was even less effective in restoring enzyme activities. In contrast, higher doses of testosterone completely reversed enzyme activity deficits, and in fact produced a significant increase in TH activity. Again, delayed testosterone replacement did not fully restore deficits in enzyme activity. In summary, the hormonal environment during the first 10 days of life is critical for the organization of HG cell number; in contrast, nuclear and cell size appear to be dependent on testosterone for activation. TH and ChAT activities also appear to be organized during this dose- and time-dependent developmental period.

Distribution of origin of nitric oxide synthase-immunoreactive nerve fibers in the rat epididymis.

Distribution of neuronal nitric oxide synthase-immunoreactive (nNOS-IR) nerve fibers and somata in the rat epididymis and major pelvic ganglia was studied by immunohistochemical methods. In the epididymis, the supply of nNOS-IR fibers was highest in the cauda and became progressively fewer toward the caput. In the cauda and corpus, nNOS-IR fibers were distributed throughout the subepithelial tissues and around the epithelial. The pattern of distribution of vasoactive intestinal polypeptide (VIP)- and tyrosine hydroxylase (TH)-immunoreactive fibers in the epididymis was similar but the latter was generally more numerous in a given region as compared to that of nNOS-IR fibers. A population of neurons in the major pelvic ganglia were nNOS-IR-, TH- or VIP-IR. Double-labeling studies revealed that few neurons in the major pelvic ganglia contained both nNOS-IR and TH-IR. Whereas nNOS-IR and VIP-IR appeared to co-localize in the same population of the pelvic ganglion cells. Similarly, nNOS-IR fibers in the epididymis were mostly VIP-positive and TH-negative. Unilateral injection of the fluorescent tracer Fluorogold into the junction between the vas deferens and the cauda labeled a population of neurons in the right and left major pelvic ganglia, some of which were also nNOS-IR. A small number of dorsal root ganglion cells contained Fluorogold and very few expressed NOS-IR. It may be concluded that nNOS-IR nerve fibers in the rat epididymis arise mainly from neurons in the major pelvic ganglia the major of which express VIP-IR but not TH-IR. The extensive supply of nNOS-immunoreactive fibers around the epithelium and throughout the subepithelial tissues suggests that NO may be closely associated with smooth muscle contraction.

Effects of low temperatures on microtubules in the non-myelinated axons of post-ganglionic sympathetic nerves.

The effect of temperature changes on the number of microtubules in non-myelinated axons has been studied in cat inferior mesenteric ganglion/hypogastric nerve preparations incubated at various temperatures in Eagles minimal essential tissue culture medium in vitro. At 37 degrees C the non-myelinated axons contained 28.4 plus or minus 0.8 S.E.M. (54) microtubules per axon. After incubation at 0 degrees C for 4 h this number fell to 2.3 plus or minus 0.1 S.E.M. (41) but returned to normal levels when the nerves were rewarmed. This loss of microtubules on cooling the nerves and their reappearance on rewarming was a rapid process; it was independent of the influence of the nueronal cell body and of protein synthesis within the axon. The preservation of the microtubules was improved when D2O was present in the incubation medium. Reformed microtubules appeared to function normally with respect to their possible role in the transport of noradrenaline storage vesicles along the axons.

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.