The sympathetic and sensory components of the caudal lumbar sympathetic trunk in the cat

The cell bodies of the lumbar sensory and sympathetic pre- and postganglionic neurons that project in the caudal lumbar sympathetic trunk of the cat have been labeled retrogradely with horseradish peroxidase applied to the central end of their cut axons. The application was made just proximal to the segmental ganglion that sends its gray rami to the L7 spinal nerve, and so identified the sympathetic outflow concerned primarily with the vasculature of the hindlimb and tail. The numbers, segmental distribution, location, and size of the labeled somata have been determined quantitatively. Labeled cell bodies were found ipsilaterally, but the segmental distributions of the different cell types were not matched. Afferent cell bodies lay in dorsal root ganglia L1-L5 (maximum L4), preganglionic cell bodies in spinal segments T10-L5 (maximum L2/3), and postganglionic cell bodies in ganglia L2-L5 (maximum L5). Both numbers and dimensions of labeled dorsal root ganglion cells were variable between experiments (maximum about 1,000); the majority were small relative to the entire population of sensory neurons. Labeled preganglionic cell bodies were located right across the intermediate region of the spinal cord, extending from the lateral part of the dorsolateral funiculus to the central canal. The highest density of labeled neurons lay at the border between the white and gray matter (corresponding to the intermediolateral cell column) with smaller proportions medially in L1-L2, and laterally in caudal L4-L5. Medial preganglionic neurons were generally larger than those lying in lateral positions. From the data, it is estimated that about 650 afferent, about 4,500 preganglionic, and some 2,500 postganglionic neurons project in each lumbar sympathetic trunk distal to the ganglion L5 in the cat.     

The afferent and sympathetic components of the lumbar spinal outflow to the colon and pelvic organs in the cat. II. The lumbar splanchnic nerves

The cell bodies of the lumbar sensory and sympathetic pre- and postganglionic neurons that project to the inferior mesenteric ganglion in the lumbar splanchnic nerves of the cat have been labeled retrogradely with horseradish peroxidase applied to the central end of their cut axons near the inferior mesenteric ganglion. The numbers, segmental distribution, location, and size of these labeled somata have been determined quantitatively. After all the lumbar splanchnic nerves on one side of an animal were labeled, most labeled cell bodies were situated ipsilaterally in dorsal root ganglia, ganglia of the lumbar sympathetic trunk, and spinal cord segments L2-L5, with the maximum numbers in L3 and L4. A few labeled somata lay contralaterally or rostral to L2. After labeling of only one lumbar splanchnic nerve, the majority of cell bodies were found in the labeled segment, but a few were also present up to three segments rostral or caudal. These variations could always be attributed to extraspinal connections usually via the lumbar sympathetic trunk. Cross-sectional areas of labeled afferent somata were small relative to those of the entire population of dorsal root ganglion cells. Preganglionic cell bodies were labeled in the intermediate gray matter extending from its lateral border ventrolaterally across to the central canal. Two regions of high density were observed: one laterally just medial to the edge of the white matter and the other lateral to the central canal. The dorsolateral group lay somewhat medial and caudal to the usual limits of the intermediolateral column. Labeled preganglionic neurons were on the average larger than the unlabeled cells in the inferior mesenteric ganglion, with the group lying medially being larger than those that were laterally positioned. From the data, it is estimated that about 4,600 afferent axons, about 4,600 preganglionic axons, and about 2,800 postganglionic axons travel in the lumbar splanchnic nerves to the inferior mesenteric ganglion of the cat.     

Afferent and sympathetic neurons projecting into lumbar visceral nerves of the male rat.

The cell bodies of thoracolumbar sensory and sympathetic pre- and postganglionic neurons that project to the colon and pelvic organs of the male rat were labeled retrogradely with horseradish peroxidase (HRP) in order to study numbers, segmental distribution, and location of the somata of these neurons quantitatively. HRP was applied to one hypogastric nerve (HGN), to the lumbar colonic nerves (LCN) and to the intermesenteric nerve (IMN). In order to estimate the significance of the branching of one axon into both hypogastric nerves a double-labeling technique with fluorogold and HRP was used. About 2640 neurons project into the two HGN added together (800 afferent, 1320 pre-, and 520 postganglionic), 4650 neurons into the LCN (360 afferent, 0 pre- and 4290 postganglionic), and 5990 into the IMN (1500 afferent, 1250 pre-, and 3240 postganglionic). About 4190 sympathetic postganglionic prevertebral neurons innervate the colon and pelvic organs, 1900 are located in the inferior mesenteric ganglion and 2290 in ganglia of the IMN. Considering the efferent component, the HGN mainly are preganglionic and the LCN exclusively postganglionic nerves. Branching of one axon into both HGN is a rare event and quantitatively negligible (less than 3%). Afferent neurons of all three nerves were found in the dorsal root ganglia (DRG) T12-L2 with the maximum in L1 and L2. The distribution of afferent neurons projecting into the LCN is shifted slightly more rostrally compared to neurons projecting into the HGN. The IMN distribution is located in a position in between. Preganglionic neurons projecting into the IMN are located in the spinal cord segments T12-L3 with the maximum in L1 and L2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distribution of splenic, mesenteric and renal neurons in sympathetic ganglia in rats

The distribution of postganglionic neurons innervating the spleen, intestine and kidney in paravertebral and prevertebral sympathetic ganglia was studied in rats using retrograde transport of fluorescent dyes. Labelled cells were counted in the thoracolumbar chain ganglia T6-L4, splanchnic ganglia and the solar plexus (fusion of left and right coeliac ganglia and superior mesenteric ganglion). Most splenic neurons were located in the splanchnic ganglion (64%), mesenteric neurons in the solar plexus (96%) and renal neurons in the sympathetic chain ganglia (80%). These three groups of neurons were distributed in overlapping ganglia within the paravertebral chain. Innervation of the spleen and intestine from the chain ganglia was bilateral, whereas innervation of the kidney was almost entirely ipsilateral. In conclusion, the sympathetic postganglionic neurons controlling the spleen, intestine and kidney have their cell bodies in different ganglia. These three groups of neurons are candidates for innervation by different subgroups of preganglionic neurons.     

Sympathetic and sensory neurons projecting into the cervical sympathetic trunk in the chicken.

The cell bodies of the sensory and sympathetic pre- and postganglionic neurons projecting into the cervical sympathetic trunk were retrogradely labeled with horseradish peroxidase in the chicken. Preganglionic neurons were located in the spinal segments T1-T6 (maximum T2), postganglionic neurons in the paravertebral ganglia T1-T3 (maximum T1) and sensory neurons in the dorsal root ganglia T1-T4 (maximum T1). Labeled preganglionic neurons were widely distributed across the intermediate gray matter and lateral funiculus, but the majority of them were located in the intermediomedial area dorsolateral to the central canal. The short and long axis diameters of labeled preganglionic neurons in this area decreased caudally. From the data of the present study, it is estimated that about 4190 preganglionic, about 450 postganglionic and about 390 sensory neurons project into the cervical sympathetic trunk cranial to the paravertebral ganglion T1 in the chicken.     

The components of the hypogastric nerve in male and female guinea pigs

A quantitative study has been made of the neural components of the hypogastric nerves of male and female guinea pigs using retrograde transport of horseradish peroxidase (HRP) to identify the population of neurones projecting in the nerve trunk, and electronmicroscopic analysis of the myelinated and unmyelinated axons present. Application of HRP to the transected axons of the hypogastric nerve labelled the cell bodies of sensory neurones in lumbar and sacral dorsal root ganglia, preganglionic neurones in the lumbar and sacral spinal cord, and postganglionic neurones in the inferior mesenteric ganglion and in the lumbar paravertebral chain; some ganglion cells of the pelvic plexus were also labelled. The number and distribution of each type of neurone with axons in the hypogastric nerve differed between the sexes: in particular, about twice as many preganglionic axons were present in the male as in the female.     

Pituitary adenylate cyclase activating polypeptide-immunoreactive sensory neurons innervate rat adrenal medulla

Rat adrenal chromaffin cells were invested by a dense network of nerve fibers immunoreactive to pituitary adenylate cyclase activating polypeptide-38 (PACAP-IR). Immunohistochemical studies demonstrated the presence of PACAP-IR in nodose and dorsal root ganglion cells, but not in neurons of the intermediolateral cell column and other autonomic nuclei of the thoracic and upper lumbar spinal cord. Somata of the T7 to T12 paravertebral ganglia were PACAP-negative. A few lightly labeled neurons were occasionally noted in the dorsal motor nucleus of the vagus. Injection of the retrograde tracer Fluorogold into the left adrenal medulla 3 days prior to sacrifice resulted in the labeling of a population of neurons in the ipsilateral spinal cord intermediolateral cell column (T1 to L1), ipsilateral and contralateral nodose ganglia and ipsilateral dorsal root ganglia from T7 to T10 inclusive. A small number of lightly labeled somata was occasionally noted in the dorsal motor nucleus of the vagus. Combined retrograde tracing and PACAP immunohistochemistry showed that a population of Fluorogold-containing nodose and dorsal root ganglion cells were also PACAP-positive. Pre-treatment of the rats with capsaicin caused a marked reduction of the PACAP-IR in the adrenal gland as well as in the superficial layers of the dorsal horn and caudal spinal trigeminal nucleus. These findings, in conjunction with the apparent absence of PACAP-IR in spinal sympathetic preganglionic neurons, sympathetic postganglionic neurons, and dorsal motor nucleus of the vagus, raise the possibility that PACAP-IR fibers observed in the adrenal medulla are primarily sensory in origin. As a corollary, catecholamine secretion from chromaffin cells may be modulated by the peptidergic sensory afferents in addition to the cholinergic sympathetic preganglionic nerve fibers.     

Secretoneurin-like immunoreactivity in rat sympathetic, enteric and sensory ganglia

Distribution of secretoneurin-like immunoreactivity (SN-LI) was studied in the rat sympathetic ganglia/adrenal gland, enteric and sensory ganglia by immunohistochemical methods. SN-LI nerve fibers formed basket-like terminals surrounding many of the postganglionic neurons of the superior cervical, stellate, paravertebral chain ganglia, coeliac/superior mesenteric and inferior mesenteric ganglia. Postganglionic neurons of the superior cervical and other sympathetic ganglia exhibited low-to-moderate levels of SN-LI. In all these sympathetic ganglia, clusters of small diameter (<10 μm) cells, which may correspond to the small intensely fluorescent (SIF) cells, were found to be intensely labeled. Surgical sectioning or ligation of the cervical sympathetic trunk for 7–10 days resulted in a nearly total loss of SN-LI fibers in the superior cervical ganglia, whereas immunoreactivity in the postganglionic neurons and small diameter cells remained essentially unchanged. In the thoracolumbar and sacral segments of the spinal cord, SN-LI nerve fibers were detected in the superficial layers of the dorsal horn as well as in the intermediolateral cell column (IL_p). Occasionally, SN-LI somata were noted in the IL_p. SN-LI nerve fibers formed a delicate plexus underneath the capsule of the adrenal gland, some of which traversed the adrenal cortex and reached the adrenal medulla. While heavily invested with SN-LI nerve terminals, chromaffin cells seemed to express a low level of SN-LI. In the enteric plexus, varicose SN-LI nerve fibers and terminals formed a pericellular network around many myenteric and submucous ganglion cells; the ganglionic neurons were lightly to moderately labeled. A population of ganglion cells in the dorsal root, nodose and trigeminal ganglia exhibited moderate-to-strong SN-LI. The detection of SN-LI in nerve fibers and somata of various sympathetic ganglia, enteric plexus and adrenal medulla and in somata of the sensory ganglia implies an extensive involvement of this peptide in sympathetic, enteric and sensory signal processing.     

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.     

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.     

Comparison of central versus peripheral nerve pathways to the guinea pig inferior mesenteric ganglion determined electrophysiologically after chronic nerve section

The contributions of central versus peripheral nerve pathways to neurons of the inferior mesenteric ganglion of guinea pigs were studied. Nerve trunks innervating neurons in the ganglion were surgically sectioned and intracellular electrical responses to nerve stimulation were measured 6-8 days after surgery. Guinea pigs were divided into two experimental groups: (1) those that had the lumbar sympathetic chain ganglia (LSG) L2 through L4 removed and (2) those that had the intermesenteric, lumbar colonic and hypogastric nerves sectioned leaving central connections intact. After 6-8 days fast excitatory postsynaptic potentials (EPSPs) and slow EPSPs were recorded intracellularly in randomly selected principal ganglionic neurons. The threshold stimulus voltage to elicit a fast EPSP, the amplitude of the slow EPSP and the number of neurons in which each type of synaptic potential occurred in response to stimulation of each of the nerve trunks was compared between surgically-sectioned animals and sham-operated controls. Neither section of preganglionic nerve trunks nor of postganglionic nerve trunks eliminated all synaptic input to neurons in the ganglion, indicating that neurons with cell bodies located central to the ganglion as well as in visceral target organs made synaptic connections in the ganglion. Both fast and slow synaptic potentials could be evoked by stimulation of postganglionic nerve trunks even after they were sectioned provided that preganglionic nerves were intact, indicating that axons of central origin which synapse in the ganglion may continue out into postganglionic nerve trunks. In like manner, evidence was obtained indicating that fibers from peripheral nerve trunks which initiate either fast or slow synaptic potentials in ganglionic neurons may continue out into the lumbar splanchnic nerves. These studies demonstrate that the synaptic potentials recorded in the inferior mesenteric ganglion arise not only from neurons with cell bodies central to the ganglion but also from neurons with cell bodies located in the visceral organs which this ganglion subserves.     

Separate populations of lumbar preganglionic neurons identified with the retrograde transport of horseradish peroxidase (HRP) and 4,6-diamidino-2-phenylindole (DAPI)

Horseradish peroxidase (HRP) was applied to the central cut end of the intermesenteric trunk or the caudal lumbar sympathetic trunk in golden hamsters. Preganglionic cells labeled from the intermesenteric trunk were located in the intermediolateral cell column, bilaterally, and in the dorsal commissural nucleus. The segmental distributions of the cells in these two nuclear groups were similar. Preganglionic neurons labeled from the lumbar sympathetic trunk were located mainly in the ipsilateral intermediolateral cell column. The simultaneous application of HRP to one trunk and 4,6-diamidino-2-phenylindole (DAPI) to the other delincated two separate preganglionic cell populations. Cells labeled from the two trunks were distributed as above. HRP-filled cells and DAPI-filled cells were intermixed in the intermediolateral cell column ipsilateral to the backfilled sympathetic trunk. No double labeled cells were present. The results show that the dorsal commissural nucleus in the lumbar cord preferentially innervates prevertebral ganglia, that lumbar paravertebral ganglia are innervated by cells located mainly in the ipsilateral intermediolateral cell column, and that paravertebral and prevertebral ganglia are innervated by non-overlapping sets of lumbar preganglionic neurons.     

Double labeling of the paravertebral sympathetic C system in the bullfrog with antisera to LHRH and NPY

The specificity of synaptic contacts between pre- and postganglionic cells in the sympathetic C system has been examined by immunocytochemical localization of two neuropeptides. Sections of bullfrog paravertebral sympathetic ganglia were stained with antibodies to luteinizing hormone releasing hormone (LHRH) and neuropeptide Y (NPY). Preganglionic synaptic boutons containing LHRH immunoreactivity were found to make contact with a subpopulation of postganglionic cell bodies and with some clusters of small intensely fluorescent (SIF) cells. In ganglia 9 and 10, 95.8% of the neurons contacted by LHRH-containing boutons were also positive for NPY-like immunoreactivity and conversely, 99.3% of the neurons that contained NPY-like immunoreactivity were contacted by LHRH-containing boutons. Qualitatively similar results were found in most other paravertebral ganglia. These observations support the conclusions that preganglionic C axons selectively innervate C-type ganglion cells and that virtually all C-type ganglion cells and some SIF cells receive a direct LHRH input. Moreover, they suggest that a pattern of specific connections between two sets of peptidergic neurons is expressed throughout most of the paravertebral sympathetic chain of the bullfrog.     

Preganglionic and sensory origins of calcitonin gene-related peptide-like and substance P-like immunoreactivities in bullfrog sympathetic ganglia

These experiments further define the organization of peptidergic pathways in the paravertebral sympathetic system of the bullfrog. Populations of axons and synaptic boutons in sympathetic ganglia 9 and 10 were found to express calcitonin gene-related peptide-like immunoreactivity (CGRP-IR) and substance P-like immunoreactivity (SP-IR). CGRP-IR is present in fibers that run through the ganglia and in boutons that make contact with almost half of the principal neurons. SP-IR is also present in fibers within the ganglia and in a rare class of synaptic boutons that are found on less than 1% of the principal neurons. Both forms of immunoreactivity are coexpressed in some nerve fibers and in the rare synaptic boutons that contain SP-IR. Neuropeptide Y-like immunoreactivity (NPY-IR), a marker for C-type postganglionic neurons, was used to identify the postsynaptic targets of boutons containing CGRP-IR and SP-IR. Ninety-five percent of the ganglion cells contacted by CGRP-IR boutons were negative for NPY-IR and are therefore likely to be B-type postganglionic neurons. Similarly, 100% of the ganglion cells contacted by boutons containing SP-IR were negative for NPY-IR. Lesions of the sympathetic chain demonstrated that synaptic boutons containing CGRP-IR arise from neurons whose axons enter the chain rostral to ganglion 7. Cutting the chain between ganglia 8 and 9 eliminates all preganglionic B and C inputs to ganglia 9 and 10. The destruction of the preganglionic C pathway by this lesion was verified by staining ganglia 9 and 10 for luteinizing hormone releasing hormone (LHRH). This lesion also eliminated boutons containing CGRP-IR and drastically reduced the number of ganglionic fibers that stained for CGRP-IR and SP-IR. By contrast, cutting the sympathetic chain between ganglia 6 and 7 spared LHRH-IR in the preganglionic C pathway but still eliminated the boutons that normally express CGRP-IR and reduced the amount of staining for SP-IR. CGRP-IR in the sympathetic ganglia arises from preganglionic and sensory neurons whereas ganglionic SP-IR is purely sensory in origin. In the spinal cord, the preganglionic B and C neurons that innervate ganglia 9 and 10 are located in different segments. In segments that contain preganglionic B cells, but not those that contain C cells, there were 243 +/- 37 (mean +/- SD) neurons in the intermediolateral cell column that express CGRP-IR. However, no cell bodies containing SP-IR were found in this region of the spinal cord.(ABSTRACT TRUNCATED AT 400 WORDS)     

Segmental distribution and central projectionsof renal afferent fibers in the cat studied by transganglionic transport of horseradish peroxidase

The segmental and central distributions of renal nerve afferents in adult cats and kittens were studied by using retrograde and transganglionic transport of horseradish peroxidase (HRP). Transport of HRP from the central cut ends of the left renal nerves labeled afferent axons in the ipsilateral minor splanchnic nerves and sensory perikarya in the dorsal root ganglia from T12 to L4. The majority of labeled cells (85%) were located between L1 and L3. A few neurons in the contralateral dorsal root ganglia were also labeled. Labeled cells were not confined to any particular region within a dorsal root ganglion. Some examples of bifurcation of the peripheral and central processes within the ganglion were noted. A small number of preganglionic neurons, concentrated in the intermediolateral nucleus, were also identified in some experiments. In addition, many sympathetic postganglionic neurons were labeled in the renal nerve ganglia, the superior mesenteric ganglion, and the ipsilateral paravertebral ganglia from T12 to L3 Transganglionic transport of HRP labeled renal afferent projections to the spinal cord of kittens from T1 1 to L6, with the greatest concentrations between Ll and L3. These afferents extended rostrocaudally in Lissauer's tract and sent collaterals into lamina I. In the transverse plane, a major lateral projection and a minor medial projection were observed along the outer and inner margins of the dorsal horn, respectively. From the lateral projection many fibers extended medially in laminae V and VI forming dorsal and ventral bundles around Clarke's nucleus. The dorsal bundle was joined by collaterals from the medial afferent projection and crossed to the contralateral side. The ventral bundle extended into lamina VII along the lateroventral border of Clarke's nucleus. Some afferents in the lateral projection could be followed ventrally into the dorsolateral portion of lamina VII in the vicinity of the intermediolateral nucleus. In the contralateral spinal cord, labeled afferent fibers were mainly seen in laminae V and VI These results provide the first anatomical evidence for sites of central termination of renal afferent axons. Renal inputs to regions (laminae I, V, and VI) containing spinoreticular and spinothajamic tract neurons may be important in the mediation of supraspinal cardiovascular reflexes as well as in the transmission of activity from nociceptors in the kidney. In addition, the identification of a bilateral renal afferent projection in close proximity to the thoracolumbar autonomic nuclei is consistent with the demonstration in physiological experiments of a spinal pathway for the renorenal sympathetic reflexes.     

Enkephalin-containing neurons in the inferior mesenteric ganglion projecting to the distal colon of cat: evidence from combined retrograde tracing by fluorescent microspheres and immunohistochemistry

Retrograde tracing with rhodamine fluorescent microspheres combined with fluorescein immunolabelling of methionine-enkephalin showed the presence of enkephalin-like material in neurons of the inferior mesenteric ganglion (sympathetic prevertebral ganglion) projecting to the distal colon in cat. Two weeks after injecting the microspheres into the wall of the distal colon, the inferior mesenteric ganglion was dissected out and incubated for 24 hours in a colchicine-containing culture medium in order to facilitate the detection of enkephalins in the soma of ganglion neurons. It was observed that retrogradely labelled ganglion cells contained enkephalin-like immunoreactive material. These ganglion cells corresponded to enkephalin-like postganglionic neurons, the terminals of which were located inside the wall of the distal colon. These enkephalin-like neurons were numerous and scattered throughout the ganglion. Sometimes enkephalin-like immunoreactive fibers, probably originating from spinal preganglionic neurons, ran close to immunoreactive and non-immunoreactive retrogradely labelled ganglion cells. This suggests that enkephalin-like immunoreactive fibers may make synaptic connections with enkephalin-like and non-enkephalin-like postganglionic neurons projecting to the distal colon. The present study establishes for the first time the existence of an enkephalin-like postganglionic pathway to the digestive tract originating from a sympathetic prevertebral ganglion. This finding indicates that the enkephalinergic innervation of the cat digestive tract may have at least two possible sources: (i) the sympathetic prevertebral ganglia; and (ii) the enteric nervous ganglia.     

Neuronal organization and cell interactions of the cat stellate ganglion.

The functional structure of the cat stellate ganglion (SG) and, in particular, its extra- and intraganglionic connections and neuronal organization, were investigated using histochemical, immunohistochemical, morphological and histological methods. Retrograde axonal transport of horseradish peroxidase was used to determine most of the extraganglionic interactions. Of the targets tested, the most extensive efferent connections of the SG were with the stemocleidomastoid muscle, trachea, esophagus and heart. Neurons of the SG also send a small number of postganglionic efferents to the thyroid and stomach. Furthermore, ganglion cells send axons to the spinal ganglia. Several afferent connections of the SG were determined. Sympathetic preganglionic neurons of segments C8-T10 of the spinal cord, sensory neurons of C8-T9 spinal ganglia, intramural ganglia of the thoracic viscera and the reticular formation of the medulla oblongata send their axons to the SG. Intraganglionic interactions of intemeurons with principal ganglionic cells were assumed to occur, based on the presence of interneurons immunoreactive to GABA and substance P. GABA- and substance P-immunoreactive fibers located around a small number of postganglionic neurons were also identified. Morphological study revealed asymmetry between the left and right ganglia: the right ganglion is larger than the left and contains more cells. This asymmetry was also reflected in basic structural parameters of neurons, such as average neuronal area and average diameter of cell somata. The present data has been used to develop a scheme for the basic inter- and intraneuronal connections of the cat SG. This ganglion is a true nervous center, with postganglionic neurons, some of which might be performing sensory functions, and interneurons. The ganglion is connected not only with the spinal cord and spinal ganglia, but also with neurons of the intramural ganglia and, by direct links, with efferent neurons of the medulla oblongata. Thus, the SG may play an essential role in viscera-visceral reflexes.     

Calbindin D28K-immunoreactivity identifies distinct subpopulations of sympathetic pre- and postganglionic neurons in the rat

Neurons performing the same function can be identified immunohistochemically because they often share the same neurochemistry. The distribution of calcium-binding proteins, like calbindin, has been used previously to identify functional subpopulations of neurons in many parts of the nervous system. In this study we have investigated the distribution of calbindin D28K-immunoreactivity in subpopulations of sympathetic preganglionic neurons in the intermediolateral nucleus of the rat spinal cord. The majority of calbindin D28K-immunoreactive preganglionic neurons also had co-localised nitric oxide synthase, although a population of preganglionic neurons in the mid- to low thoracic intermediolateral nucleus expressed only calbindin D28K-immunoreactivity. Retrograde-tracing studies showed that calbindin D28K-immunoreactive neurons projected to the superior cervical and stellate ganglia, with smaller numbers of cells projecting to the lumbar sympathetic chain and superior mesenteric ganglia. Very few calbindin D28K-immunoreactive neurons projected to the inferior mesenteric ganglion, and none projected to the adrenal medulla. The distribution of calbindin D28K-immunoreactive terminals and postganglionic neurons in the superior cervical and stellate ganglia was also investigated. Many postganglionic neurons were calbindin D28K-immunoreactive, and most of these lacked neuropeptide Y-immunoreactivity. Calbindin D28K-immunoreactive nerve terminals were common and formed dense pericellular baskets around many postganglionic neurons, including some of those that were calbindin D28K-immunoreactive, but only rarely formed pericellular baskets around neuropeptide Y-immunoreactive neurons. The function of some of the classes of postganglionic neurons that were the target of calbindin D28K-immunoreactive preganglionic terminals was determined by combining immunohistochemistry with retrograde-tracer injections into a range of peripheral tissues. Calbindin D28K-immunoreactive nerve terminals, with co-localised nitric oxide synthase-immunoreactivity, surrounded secretomotor neurons projecting to the submandibular salivary gland and pilomotor neurons projecting to skin, but did not surround neurons projecting to brown fat or vasomotor neurons projecting to the skin, muscle, or salivary glands. J. Comp. Neurol. 386:245–259, 1997. © 1997 Wiley-Liss, Inc.     

The distribution of nitric oxide synthase-containing autonomic preganglionic terminals in the rat

Nitric oxide synthase (NOS)-immunoreactivity was co-localised with NADPH diaphorase activity in preganglionic sympathetic neurons and in their terminals in pre- and paravertebral sympathetic ganglia. The density of NOS-containing terminals varied between ganglia. Reactive terminals were densestin the superior cervical, stellate and inferior mesenteric ganglia, where the majority of the neurons were surrounded by reactive fibres, and the coeliac and superior mesenteric ganglia, where about half the postganglionic somata were sorrounded by reactive terminals. Fibres were least abundant in the pelvic ganglia and thoracic and lumbar sympathetic chain ganglia. NOS reactivity did not coincide with the distribution of calcitonin gene related peptide immunoreactivity, a marker for the terminals of NOS-containing sensory neurons in the rat. The distribution of nerve cells and terminals suggests that NOS is present in more than one functional subpopulation of sympathetic preganglionic neurons.