Origin Of Nerve Fibers Research Articles

Visualizing the Calcitonin Gene-Related Peptide Immunoreactive Innervation of the Rat Cranial Dura Mater with Immunofluorescence and Neural Tracing.

The aim of this study was to examine the distribution and origin of the calcitonin gene-related peptide (CGRP)-immunoreactive sensory nerve fibers of the cranial dura mater using immunofluorescence, three-dimensional (3D) reconstruction and retrograde tracing technique. Here, the nerve fibers and blood vessels were stained using immunofluorescence and histochemistry techniques with CGRP and fluorescent phalloidin, respectively. The spatial correlation of dural CGRP-immuoreactive nerve fibers and blood vessels were demonstrated by 3D reconstruction. Meanwhile, the origin of the CGRP-immunoreactive nerve fibers were detected by neural tracing technique with fluorogold (FG) from the area around middle meningeal artery (MMA) in the cranial dura mater to the trigeminal ganglion (TG) and cervical (C) dorsal root ganglia (DRGs). In addition, the chemical characteristics of FG-labeled neurons in the TG and DRGs were also examined together with CGRP using double immunofluorescences. Taking advantage of the transparent whole-mount sample and 3D reconstruction, it was shown that CGRP-immunoreactive nerve fibers and phalloidin-labeled arterioles run together or separately forming a dural neurovascular network in a 3D view, while the FG-labeled neurons were found in the ophthalmic, maxillary, and mandibular branches of TG, as well as the C2-3 DRGs ipsilateral to the side of tracer application in which some of FG-labeled neurons presented with CGRP-immunoreactive expression. With these approaches, we demonstrated the distributional characteristics of CGRP-immunoreactive nerve fibers around the blood vessels in the cranial dura mater, as well as the origin of these nerve fibers from TG and DRGs. From the perspective of methodology, it may provide a valuable reference for understanding the complicated neurovascular structure of the cranial dura mater under the physiological or pathological condition.

Distribution and origin of TRPV1 receptor-containing nerve fibers in the dura mater of rat

We examined the distribution and origin of the nerve fibers innervating the dura mater of the rat that show immunoreactivity for the TRPV1 receptor (TRPV1-IR). Nearly 70% of the nerve fibers showing TRPV1-IR in the dura mater also exhibited CGRP-IR. Using a combination of immunohistochemistry and a retrograde tracer technique, we detected tracer accumulation in 0.6% of the neurons in the trigeminal ganglion and a few neurons in the dorsal root ganglion; half of the neurons in the trigeminal ganglion were small- and medium-sized (≤ 1000 μm 2). Among the tracer-accumulated neurons in the trigeminal ganglion, approximately 25% exhibited TRPV1-IR. Furthermore, nearly 80% of the tracer-accumulated small- and medium-sized neurons in the trigeminal ganglion that exhibited TRPV1-IR also exhibited CGRP-IR. Our findings indicate that the TRPV1 receptor in the dura mater and sensory ganglia may contribute to the pathophysiology of migraine, providing an important clue for the development of therapeutic strategies for migraine.

Immunohistochemical features of substance P-immunoreactive chromaffin cells and nerve fibers in the rat adrenal gland

The distribution of substance P (SP) immunoreactivity and the colocalization of SP with other bioactive substances in chromaffin cells and nerve fibers were investigated in the rat adrenal gland at the light microscopic level. In the capsule and cortex, SP immunoreactivity was seen in some nerve fibers around blood vessels and in thick nerve bundles passing through the cortex directly into the medulla. In the medulla, the SP immunoreactivity was observed in a small number of chromaffin cells; these SP-immunoreactive chromaffin cells were either phenylethanolamine N-methyltransferase (PNMT) immunoreactive or immunonegative, indicating that they were either adrenaline cells or noradrenaline (NA) cells. SP-immunoreactive varicose nerve fibers were also found in the medulla and were in contact with a cluster of the NA cells showing catecholamine fluorescence, which suggests that SP from medullary nerve fibers may regulate the secretory activity of the NA cells. Because no SP-immunoreactive ganglion cell was present in the rat adrenal gland, the intra-adrenal nerve fibers were considered to be extrinsic in origin. The double-immunostaining method further revealed that the SP-immunoreactive chromaffin cells also exhibit immunoreactivities for calcitonin gene-related peptide (CGRP), and neuropeptide tyrosine (NPY), suggesting that these peptides can also be released from the chromaffin cells by certain stimuli. The intra-adrenal nerve fibers in the medulla were composed of SP-single immunoreactive, and SP/CGRP-, SP/choline acetyltransferase (ChAT)-, SP/nitric oxide synthase (NOS)-, SP/pituitary adenylate cyclase activating polypeptide (PACAP)-, ChAT/NOS-, and ChAT/PACAP-immunoreactive nerve fibers, which may affect the secretory activity of the NA cells. In the adrenal capsule, the nerve fibers were present around blood vessels and showed immunoreactivities for SP/ CGRP, SP/NPY, SP/NOS, and SP/vasoactive intestinal polypeptide, suggesting that the origin of nerve fibers in the capsule may differ from those in the medulla.

Combined determination with functional and morphological studies of origin of nerve fibers expressing transient receptor potential vanilloid 1 in the myenteric plexus of the rat jejunum

The aim of this study was to determine the action of capsaicin in isolated rat intestine and the origin of nerve fibers expressing transient receptor potential vanilloid 1 (TRPV1: capsaicin receptor) in the rat jejunum by combination of functional and immunohistochemical experiments. Capsaicin (1 μM) produced a prolonged relaxation response (52.8±15.3% of the relaxation response to papaverine, mean±S.D., n=27) of the isolated jejunum in the presence of atropine and guanethidine. Pretreatment with the TRPV1 antagonist, capsazepine (10 μM) and ruthenium red (3 μM) significantly reduced the relaxation response to capsaicin by 78% ( P<0.01) and 38% ( P<0.05), respectively. Tetrodotoxin and calcitonin gene-related peptide (CGRP)-desensitization significantly reduced the response to capsaicin by 72% ( P<0.01) and 42% ( P<0.01), respectively. Therefore, we investigated the distribution of TRPV1-immunoreactivity (IR) in the myenteric plexus of the rat jejunum. Using antisera raised against either the N-terminal or C-terminal domains of rat TRPV1, TRPV1-IR was present in the nerve fibers, but not in the cell bodies of myenteric neurons. These TRPV1-immunoreactive nerve fibers were running in myenteric ganglia and their interconnecting strands. Most TRPV1-immunoreactive nerve fibers showed CGRP-IR, whereas few VR1-immunoreactive nerve fibers showed substance P-IR. After chronic denervation of the extrinsic nerve supply to the jejunum, both the relaxation response to capsaicin and TRPV1-immunoreactive nerve fibers completely disappeared. These findings indicate that these TRPV1-immunoreactive nerve fibers in the rat jejunum derive from extrinsic neurons and that activation of TRPV1 produces the relaxation response in the rat jejunum, at least in part, through the release of CGRP from nerve fibers expressing TRPV1.

Origin of PACAP-immunoreactive nerve fibers innervating the subarachnoidal blood vessels of the rat brain.

The subarachnoidal cerebral blood vessels of the rat are innervated by nerve fibers containing different neuropeptides, e.g. pituitary adenylatecyclase activating polypeptide (PACAP). PACAP dilates brain arterioles and immunohistochemical studies of the rat have indicated that PACAP binds to a VPAC1-receptor in the cerebral vasculature of this species. We have investigated the perikaryal origin of the nerve fibers innervating the subarachnoidal blood vessels of the rat by combined retrograde tracing with Fluorogold and immunohistochemistry. The in vivo neuronal retrograde tracings were done by injection of 2% Fluorogold in water into the subarachnoidal space in the area of the middle cerebral artery. The retrograde transported tracer was detected by use of an antibody against Fluorogold. One week after the injections, the animals were vascularly perfused with Stephanini's fixative and labeled perikarya were found bilaterally in the trigeminal, sphenopalatine, and otic ganglia. The retrograde Fluorogold tracings were combined with immunohistochemistry for PACAP using a mouse monoclonal antibody and the biotinylated tyramide amplification system. Double labeled perikarya containing both Fluoro-gold and PACAP were found predominantly in the trigeminal ganglion, and only rarely in the otic and sphenopalatine ganglion. Summarizing, our retrograde tracings combined with immunohistochemistry indicate that the perikarya in the trigeminal ganglion are the main origin of PACAPergic nerve fibers projecting to the cerebral vasculature of the rat.

Neuroepithelial cells and associated innervation of the zebrafish gill: a confocal immunofluorescence study.

Peripheral chemoreceptors responsive to hypoxia have been well characterized in air-breathing vertebrates, but poorly in water-breathers. The present study examined the distribution of five populations of neuroepithelial cells (NECs), putative O(2) chemoreceptors, and innervation patterns in the zebrafish gill using whole-mounts and confocal immunofluorescence. Nerve bundles and fibers of the gill were labeled with zn-12 (a zebrafish-specific neuronal marker) and SV2 antisera and NECs were characterized by serotonin (5-HT) immunoreactivity (IR), SV2-IR and the purinoceptor P2X(3)-IR. A zn-12-IR nerve bundle extended the length of the gill filament and gave rise to a nerve plexus surrounding the efferent filament artery (eFA) and a rich network of fibers that innervated both serotonergic and nonserotonergic NECs of the filament and lamellar epithelium. Three populations of serotonergic, SV2-IR neurons intrinsic to the gill filaments are described, one of which provided innervation to NECs of the filament epithelium. Degeneration of nerve fibers in gill arches maintained in explant culture for 2 days revealed the extrinsic origin of nerve fibers of the plexus and lamellae and the innervation of filament NECs by both intrinsic and extrinsic fibers. Intrinsic innervation surrounding the eFA survived in explant cultures, suggesting a mechanism of local vascular control within the gill. In addition, NECs survived in explants after degeneration of extrinsic nerve fibers. Thus, NECs of the zebrafish gill are organized in a manner reminiscent of O(2) chemoreceptors of mammalian vertebrates, suggesting a role in respiratory regulation.

Sensory innervation of the sacroiliac joint in rats.

The segmental levels of dorsal root ganglions innervating the sacroiliac joint in rats were investigated using the retrograde transport method. The pathways and functions of the nerve fibers supplying the sacroiliac joint were determined by immunohistochemical detection of transported tracer. To study the sensory innervation of the sacroiliac joint and to elucidate the neural pathways of low back pain originating from the sacroiliac joint. The sacroiliac joint is a possible source of low back pain. The L4-S4 spinal nerves have been regarded as the nerves innervating the sacroiliac joint in humans. However, the origins of nerve fibers have not been analyzed experimentally with tracer methods. Cholera toxin B subunit, a neural tracer, was injected into the left sacroiliac joint of adult rats, and the bilateral dorsal root ganglions were immunohistochemically examined 4 days after injection. In another rat group, the dorsal root ganglions were examined using the same methods after resection of the left sympathetic trunk from L2 to the most caudal level. Thus, the pathways of the nerve fibers supplying the sacroiliac joint were investigated. Labeled neurons were mainly located in the ipsilateral dorsal root ganglions from L1 to S2 of the unsympathectomized rats and in the ipsilateral dorsal root ganglions from L4 to S2 of the sympathectomized rats. The sacroiliac joint was innervated by sensory neurons in dorsal root ganglions ipsilateral to the joint from L1 to S2. Sensory fibers from the L1 and L2 dorsal root ganglions passed through the paravertebral sympathetic trunk.

The vagal origin of preganglionic fibers containing nitric oxide synthase in the guinea-pig heart

The origin of nerve fibers projecting to the guinea pig heart that contain nitric oxide synthase (NOS) were studied by unilateral cervical vagotomy. Three kinds of NOS-immunoreactive (NOS-ir) nerve fibers are distributed in the control guinea pig heart: the sparse network covering the right atrium, the basket-like endings around intracardiac neuronal cell bodies in the small ganglia located in the left atrium and the interatrial septum, and the axons situated in the septal region. The sparse network in the right atrium did not change after vagotomy of right or left side. In the whole mount preparations of right atrium, we often traced labeled axons from the somata to join the network covering the right atrium. Therefore, most of this network of labeled fibers must be of intrinsic origin. Because the basket-like endings around neuronal cell bodies in the ganglia in the left atrium and the septum disappeared completely after vagotomy of left side, we conclude that they are parasympathetic preganglionic fibers originating from the left vagus nerve. NOS-ir cell bodies and the positive fibers in the atrioventricular nodal region survived after vagotomy. All of such nerve fibers were unmyelinated axons. Therefore, they seem to be the postganglionic fibers arising from the ganglia located in the left atrium or the septum.

Distribution and origin of nerve fibers in the rat temporomandibular joint capsule.

The distribution and origin of nerve fibers containing neuropeptides and NOS projecting to the temporomandibular joint capsule (TMJ) of the rat were studied by retrograde tracing in combination with immunocytochemistry. Numerous nerve fibers were seen in the TMJ as revealed by the neuronal marker protein gene product 9.5. Nerve fibers containing neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), pituitary adenylate cyclase activating peptide (PACAP), substance P (SP), calcitonin gene-related peptide (CGRP), and nitric oxide synthase (NOS) were seen in the synovial membrane, the joint capsule and entering the articular disc. Injection of the retrograde tracer True Blue (TB) into the TMJ resulted in the appearance of numerous labeled nerve cell bodies in the trigeminal and superior cervical ganglia, and moderate numbers in the nodose, the otic, the sphenopalatine, the stellate and the dorsal root ganglia at levels C2-C5. Most of the TB-labeled cell bodies in the superior cervical and stellate ganglia contained NPY. In the trigeminal ganglion, numerous TB labeled cell bodies contained CGRP and a minor population stored SP, a few cell bodies were seen to store NOS or PACAP. In the sphenopalatine and otic ganglia, TB labeled cell bodies contained NOS or VIP. In the nodose ganglion, labeled cell bodies contained CGRP; other labeled cell bodies harbored NOS. In the cervical dorsal root ganglia, the majority of the labeled cell bodies stored CGRP and smaller populations stored SP and PACAP. Thus, the innervation of the TMJ is complex and many different ganglia are involved.

Origins of nerve fibers containing nitric oxide synthase in the rat celiac-superior mesenteric ganglion.

The origin of nitric oxide synthase-containing nerve fibers in rat celiac-superior mesenteric ganglion was examined using retrograde tracing techniques combined with the immunofluorescence method. Fluoro-Gold was injected into the celiac-superior mesenteric ganglion. Neuronal cell bodies retrogradely labeled with Fluoro-Gold in the thoracic spinal cord, the dorsal root ganglia at the thoracic level, the nodose ganglion, and the intestine from the duodenum to the proximal colon were examined for nitric oxide synthase immunoreactivity. About 60% of sympathetic preganglionic neurons in the intermediolateral nucleus projecting to the celiac-superior mesenteric ganglion were immunoreactive for nitric oxide synthase, as were approximately 27% of nodose ganglion neurons and about 65% of dorsal root ganglion neurons projecting to the celiac-superior mesenteric ganglion. Neurons projecting to the celiac-superior mesenteric ganglion were found in the myenteric plexus of the small and large intestine. In the proximal colon, about 23% of such neurons were immunoreactive for nitric oxide synthase. However, in the small intestine, no immunoreactivity was found in these neurons.

Origins of nerve fibers containing nitric oxide synthase in the rat celiac-superior mesenteric ganglion

Origins of nerve fibers containing nitric oxide synthase in the rat celiac-superior mesenteric ganglion

The distribution and origin of nerve fibers immunoreactive for substance P and neurokinin A in the anterior buccal gland of the rat

The distribution and origin of nerve fibers immunoreactive for substance P and neurokinin A in the anterior buccal gland of the rat

The major pelvic ganglion is the main source of nitric oxide synthase-containing nerve fibers in penile erectile tissue of the rat

The possible implication of nitric oxide synthase (NOS) in penile erection was examined by utilizing NADPH histochemistry in the rat. NADPH histochemistry indicated that the major pelvic ganglion (MPG), a well-known origin of nerve fibers supplying the external genitalia, contained many NOS-positive neurons. On the other hand, NOS-positive nerve fibers in penile erectile tissue observed in the walls of both arteries and veins, as well as in intrinsic smooth muscles. The retrograde tracing study with Fluoro-Gold (FG) in combination with NADPH histochemistry revealed that almost all MPG neurons which were retrogradely labeled with FG injected into the penile crura were NOS-positive. Thus, the MPG was considered to be the main source of NOS-positive nerve fibers in penile erectile tissue.

Fine structure and possible origins of nerve fibers with corticotropin-releasing factor-like immunoreactivity in the rat central amygdaloid nucleus

The fine structure of nerve fibers with corticotropin-releasing factor (CRF)-like immunoreactivity in the central amygdaloid nucleus and CRF-containing afferents to the nucleus were investigated by pre-embedding immunoelectron microscopy and by the combination of fluoro-gold tracing and the indirect immunofluorescence method. Significant numbers of CRF nerve endings and dendrites formed synapses with non-immunoreactive dendrites and axon terminals, respectively. Axon terminals devoid of CRF frequently made synapses with the soma of immunoreactive and non-immunoreactive neurons; CRF nerve endings in contact with the soma were fewer in number. Occasionally, CRF was localized to both pre- and postsynaptic structures in the central amygdaloid nucleus. After flouro-gold injection into the central amygdaloid nucleus and adjacent areas, double-labeled cells with the tracer and CRF were observed mainly in the lateral hypothalamic area and occasionally in the dorsal raphe nucleus, and they were less numerous than single-labeled cells. These findings suggest that part of the CRF axon terminals identified in the electron micrographs arises from neurons in the lateral hypothalamic area and the dorsal raphe nucleus and the others from intra-amygdaloid CRF neurons. The immunoreactive dendrites are likely to derive from neurons in the central amygdaloid nucleus, which are shown to send axons to the lower brainstem. Thus, this study demonstrates that CRF structures constitute a more complex neuronal network in the central amygdaloid nucleus than previously considered.

Axonal tracing of autonomic nerve fibers to the superficial temporal artery in the rat

The origin of nerve fibers to the superficial temporal artery of the rat was studied by retrograde tracing with the fluorescent dye True Blue (TB). Application of TB to the rat superficial temporal artery labeled perikarya in the superior cervical ganglion, the otic ganglion, the sphenopalatine ganglion, the jugular-nodose ganglionic complex, and the trigeminal ganglion. The labeled perikarya were located in ipsilateral ganglia; a few neuronal somata were, in addition, seen in contralateral ganglia. Judging from the number of labeled nerve cell bodies the majority of fibers contributing to the perivascular innervation originate from the superior cervical, sphenopalatine and trigeminal ganglia. A moderate labeling was seen in the otic ganglion, whereas only few perikarya were labeled in the jugular-nodose ganglionic complex. Furthermore, TB-labeled perikarya were examined for the presence of neuropeptides. In the superior cervical ganglion, all TB-labeled nerve cell bodies contained neuropeptide Y. In the sphenopalatine and otic ganglia, the majority of the labeled perikarya were endowed with vasoactive intestinal polypeptide. In the trigeminal ganglion, the majority of the TB-labeled nerve cell bodies displayed calcitonin gene-related peptide, while a small population of the TB-labeled neuronal elements contained, in addition, substance P. In conclusion, these findings indicate that the majority of peptide-containing nerve fibers to the superficial temporal artery originate in ipsilateral cranial ganglia; a few fibers, however, may originate in contralateral ganglia.

Retrograde Tracing of Nerve Fibers to the Rat Middle Cerebral Artery with True Blue: Colocalization with Different Peptides

The origin of nerve fibers to the rat middle cerebral artery was studied by retrograde tracing with the fluorescent tracer True Blue (TB) in combination with immunocytochemistry to known perivascular peptides. Application of TB to the middle cerebral artery labeled nerve cell bodies in the ipsilateral superior cervical ganglion, the otic ganglion, the sphenopalatine ganglion, the trigeminal ganglion, and the cervical dorsal root ganglion at level C2. A few labeled nerve cell bodies were seen in contralateral ganglia. Judging from the number and intensity of the labeling, the superior cervical ganglion and the trigeminal ganglion and dorsal root ganglion at level C2 contributed most to the innervation. A moderate number of nerve cell bodies were labeled in the sphenopalatine and otic ganglia. The TB-labeled nerve cell bodies were further examined for the presence of neuropeptides. For that purpose antibodies raised against neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), substance P (SP) and calcitonin gene-related peptide (CGRP) were used. A considerable portion of the TB-labeled nerve cell bodies in the superior cervical ganglion contained NPY. About half of the labeled nerve cell bodies in the sphenopalatine and otic ganglia contained VIP. In the trigeminal ganglion and in the dorsal root ganglion at level C2, one-third of the TB-labeled nerve cell bodies were CGRP-immunoreactive, while only few nerve cell bodies contained SP. The study provides direct evidence for the origin of cerebrovascular peptidergic nerve fibers and demonstrates that not only ipsilateral but also contralateral ganglia contribute to the innervation of the cerebral circulation.

Neuronal pathways to the rat middle meningeal artery revealed by retrograde tracing and immunocytochemistry

The origin of nerve fibers to the middle meningeal artery of rat was studied by retrograde tracing in combination with immunocytochemistry. Application of the retrograde tracer, True blue (TB), to the middle meningeal artery labeled nerve cell bodies in the ipsilateral superior cervical ganglion, the otic ganglion, the sphenopalatine ganglion, the jugular-nodose ganglionic complex, the trigeminal ganglion and the cervical dorsal root ganglion at level C 2. A few nerve cell bodies were labeled in the contralaterally placed ganglia. Judging from the number of labeled nerve cell bodies, the ipsilateral superior cervical ganglion, the otic ganglion, the sphenopalatine and the trigeminal ganglia contribute most to its innervation. A moderate supply of labeled nerve cell bodies was seen in the cervical dorsal root ganglion at level C 2 whereas there were only few in the jugular-nodose ganglionic complex. The TB-labeled nerve cell bodies were further examined for the presence of neuropeptides. For that purpose antibodies against neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and substance P (SP) were used. Most of the TB-labeled nerve cell bodies in the superior cervical ganglion exhibited NPY-immunoreactivity. In the sphenopalatine and otic ganglia the majority of the TB-labelled neurons were VIP-immunoreactive whereas in the trigeminal and dorsal root ganglion at level C 2 the majority of labeled nerve cell bodies displayed CGRP-immunofluorescence and a minority of the labeled nerve cell bodies were substance P-immunoreactive. Together the findings indicate that several ganglia project to the middle meningeal artery of the rat and that many neuropeptides are involved in vasomotor control and in mediation of afferent information.

Sensory innervation of the ear drum and middle-ear mucosa: Retrograde tracing and immunocytochemistry

The distribution and origin of nerve fibers of presumed sensory nature in the ear drum and middle-ear mucosa of the rat were studied by a retrograde tracing technique in combination with immunocytochemistry. Application of True Blue (TB) on the ear drum or on the middle-ear mucosa labeled nerve cell bodies in the jugular, trigeminal, geniculate and cervical dorsal root ganglia (C2-C4). Judging from the number of TB-labeled nerve cell bodies the jugular and trigeminal ganglia contributed the major component to the sensory innervation of the ear drum and the middle-ear mucosa, while the contribution from the geniculate and cervical dorsal root ganglia was relatively minor. The majority of the TB-labeled nerve cell bodies contained calcitonin gene-related peptide (CGRP), whereas minor populations stored substance P (SP) and neurokinin A (NKA). Nerve fibers containing SP, NKA and CGRP were moderate in number in the middle-ear mucosa and few in the ear drum. Double immunostaining revealed that SP invariably coexisted with NKA in nerve cell bodies in the ganglia examined. The SP/NKA-containing nerve cell bodies constituted a subpopulation of those storing CGRP. The findings indicate that several ganglia project to the ear drum and middle-ear mucosa and that many neuropeptides are involved in the mediation of middle-ear sensitivity.

Origin and morphology of nerve fibers the aganglionic colon of the lethal spotted (ls/ls) mutant mouse

The lethal spotted mutant mouse (ls/ls) develops congenital megacolon because of the absence of ganglia in the terminal colon. This aganglionosis results from a failure of neural crest cells to colonize this area during fetal life. We have postulated that the microenvironment of the aganglionic segment of bowel is abnormal. Our hypothesis suggests that this abnormal enteric microenvironment fosters the sprouting of neuritic processes. We further propose that neural and glial precursors cease to migrate once they have extended their definitive processes. As a result, the area distal to the site where neurite extension is favored does not become colonized by neural or glial precursors. A prediction of this hypothesis is that the aganglionic tissue should be innervated by axons from neurons located both in the more proximal ganglionated bowel and in ganglia located outside the gut. Neurons and their processes in control and ls/ls terminal gut were located by the histochemical demonstration of acetylcholinesterase (AChE) activity and their structure was classified as intrinsic (enteric) or extrinsic in type by electron microscopy. In ls/ls mice the submucosal plexus was much more severely affected than the myenteric plexus. No submucosal ganglia were found within 30 mm of the anus. In contrast, myenteric ganglia extended to within 4 mm of the anus on the mesenteric side of the gut and to within 15 mm on the antimesenteric side. Rostral to the areas that were absolutely aganglionic, both plexuses were hypoganglionic, especially the submucosal plexus, which was hypoganglionic throughout the entire colon. Both the aganglionic and caudal hypoganglionic zones of the ls/ls bowel were penetrated by large nerve trunks that had the ultrastructural characteristics of extra-enteric peripheral nerve. Unusual ganglia, outside the enteric musculature in the adventitia of the colon, were connected to these trunks. The location of the cell bodies of origin of the nerve fibers in the terminal colon of control mice and in the aganglionic segment of the bowel in ls/ls mice was determined by following the retrograde transport of tracers injected as close as possible to the anus. An extrinsic innervation originating from the inferior mesenteric ganglion and dorsal root ganglia (L6-S1) was found in both types of animal. In control but not ls/ls mice retrograde labeling was also observed in the sacral parasympathetic nucleus of the spinal cord. In addition, neuritic processes were traced to neurons in myenteric ganglia. In control mice, these labeled neurons were present in ganglia within the injection site as well as in bowel rostral and caudal to it.(ABSTRACT TRUNCATED AT 400 WORDS)

Origins of Peptide and Norepinephrine Nerves in the Mucosa of the Guinea Pig Small Intestine

Norepinephrine, acetylcholine, and certain peptides are contained in mucosal nerves and have potent effects on transepithelial water and electrolyte fluxes. It is difficult to ascribe roles for these nerves as their sources are unknown. The present studies were undertaken to determine the origins of nerve fibers that are found in the mucosa of the guinea pig small intestine and which contain one of the following substances: vasoactive intestinal peptide, substance P, somatostatin, neuropeptide Y, cholecystokinin, or norepinephrine. Nerve fiber origins were ascertained by making lesions to sever pathways through which the nerves could reach the mucosa. The lesioning operations were homotopic autotransplants of short (2 cm) segments of intestine; myectomies, in which a 5-10-mm length of intestine was stripped of longitudinal muscle and myenteric plexus; and extrinsic denervation, in which nerves reaching the intestine through the mesentery were severed. The results of these studies, considered along with previously published work, led to the upcoming conclusions. Nerve fibers in the mucosa showing immunoreactivity for vasoactive intestinal peptide, somatostatin, cholecystokinin, and neuropeptide Y arise from cell bodies in the overlying submucous plexus. Substance P fibers arise in part from the overlying submucous plexus and in part from the overlying myenteric plexus. Mucosal norepinephrine fibers arise from extrinsic sympathetic ganglia. Enkephalin, gastrin-releasing peptide, and 5-hydroxytryptamine, which are in some enteric nerves, are not found in submucous nerve cells and few, if any, fibers containing these substances supply the mucosa. Thus, the mucosa receives a dense nerve supply, much of which arises locally from submucous ganglia.