Use of the fluorescent dye, fast blue, to label sympathetic postganglionic neurones supplying mesenteric arteries and enteric neurones of the rat

Sympathetic innervation of the development, maturity, and aging of the gastrointestinal tract

The sympathetic nervous system inhibits gut motility, secretion, and blood flow in the gut microvasculature and can modulate gastrointestinal inflammation. Sympathetic neurons signal via catecholamines, neuropeptides, and gas mediators. In the current review, we summarize the current understanding of the mature sympathetic innervation of the gastrointestinal tract with a focus mainly on the prevertebral sympathetic ganglia as the main output to the gut. We also highlight recent work regarding the developmental processes of sympathetic innervation. The anatomy, neurochemistry, and connections of the sympathetic prevertebral ganglia with different parts of the gut are considered in adult organisms during prenatal and postnatal development and aging. The processes and mechanisms that control the development of sympathetic neurons, including their migratory pathways, neuronal differentiation, and aging, are reviewed.

Experimental study on the location of neurons associated with the first sacral sympathetic trunk ganglion of the pig

The neurons associated with the left first sacral sympathetic trunk ganglion (STG S1), an autonomic ganglion particularly concerned in the innervation of the smooth and striated musculature associated with pelvic organs, were identified in the pig, using the non-trans-synaptic fluorescent retrograde neuronal tracer Fast Blue. The labelled neurons were located mostly ipsilaterally, in the intermediolateral nucleus of the spinal cord segments T10-L5, in the sympathetic trunk ganglia L3-Co1, in the caudal mesenteric ganglia, in the pelvic ganglia, and in the spinal ganglia T13-S4. Our results could indicate the existence of visceral neuronal circuits concerning the ganglia of the sympathetic trunk and the caudal mesenteric, pelvic and spinal ganglia with or without the intervention of the central nervous system, whose identification and preservation during surgical treatments could be helpful in reducing the risk of subsequent urinary and sexual disfunctions.

Absence of cholinergic sympathetic innervation from limb muscle vasculature in rats and mice

Although the existence of cholinergic sympathetic vasodilatory innervation in limb muscle vasculature is well established for some species, previous pharmacological studies have failed to reveal the presence of such innervation in rats. Recently, Schafer and colleagues [Schafer, M.K., Eiden, L.E., Weihe, E., 1998. Cholinergic neurons and terminal fields revealed by immunohistochemistry for the vesicular acetylcholine transporter. II. The peripheral nervous system. Neuroscience 84(2), 361-376] reported that vesicular acetylcholine transporter immunoreactivity (VAChT-IR), a marker for cholinergic terminals, is present in the innervation of the microvasculature of rat hindlimb skeletal muscle and concluded that rats possess cholinergic sympathetic innervation of limb muscle vasculature. Because of our interest in identifying targets of cholinergic sympathetic neurons, we have analyzed the transmitter properties of the innervation of muscle vessels in rat and mouse limbs. We found that the innervation of vasculature in muscle is noradrenergic, exhibiting robust catecholamine histofluorescence and immunoreactivity for tyrosine hydroxylase (TH) and the peptide transmitters, neuropeptide Y (NPY) and occasionally vasoactive intestinal peptide (VIP). In contrast, cholinergic phenotypic markers,VAChT-IR and acetylcholinesterase (AChE) activity, are absent. Neuron cell bodies in sympathetic ganglia, retrogradely labeled with injections of tracer into limb muscles, also lacked VAChT but contained TH-IR. The innervation of large extramuscular feed arteries in hindlimbs was also devoid of cholinergic markers, as were the cell bodies of sympathetic neurons innervating extramuscular femoral arteries. These results, like those of previous physiological studies, provide no evidence for the presence of cholinergic sympathetic innervation of muscle vasculature in rats or mice.

Localization of sympathetic postganglionic neurons innervating mesenteric artery and vein in rats

Physiological and histochemical studies have demonstrated the control and innervation of sympathetic nerves to the artery and vein vessels of splanchnic circulation. In our laboratory, we first used the technique of retrograde transport of horseradish peroxidase to identify the origin of sympathetic neurons innervating the mesenteric vein. In this study, double fluorescence staining technique was used for a simultaneous localization of the sympathetic postganglionic neurons supplying the mesenteric artery and vein in rats. First-order branches of mesenteric artery (A) and vein (V) in the vicinity of ileo-cecal junction were isolated for application of fluorescent dyes (Fast Blue, FB and Diamidino Yellow, DY). The application of FB and DY on A and V was alternated in the next animal to minimize the difference in dye uptake. The animal was allowed to recover for 6-7 days assuring a complete uptake of FB and DY into the cytoplasm and nucleus, respectively. The number of FB, DY and double staining neurons in the prevertebral and paravertebral ganglia were counted under a fluorescent microscope after animal fixation and serial frozen section (30 microm) of the sympathetic ganglia. Our study revealed the following findings: (1) Distribution of the fluorescence-staining neurons in the sympathetic ganglia was as follows: right celiac ganglion (39%), superior mesenteric ganglion (30%), left celiac ganglion (26%), inferior mesenteric ganglion (1%) and paravertebral ganglia (4%). (2) Double staining neurons that dually innervate A and V amounted to 54% of total staining neurons. There were 41% neurons singly innervating A and 5% innervating V. (3) The ratio of neurons supplying the A and V ranged from 1.41 to 1.75 (average 1.61). (4) There was no distinct topographical distribution with respect to the neuron location innervating A and V. The distribution of neurons appeared in a scattering pattern.

Projections from the prevertebral and major pelvic ganglia to the ileum and large intestine of the male rat

The sympathetic innervation of the gut arises from the prevertebral and pelvic ganglia, and to a variable extent, from neurons located in the paravertebral ganglia, the splanchnic and intermesenteric nerves. In this study we have injected retrograde tracers into the wall of the ileum and several regions of the large intestine to determine the proportion of neurons supplying these regions from each of the ganglia and nerves. The sympathetic supply to the ileum arises primarily from neurons in the splanchnic nerves and the paravertebral ganglia T9-T11 (SPL) and the coeliaco-mesenteric ganglion complex (CG/SMG), with a small supply from the proximal intermesenteric nerves (IMN). The distribution of neurons projecting to the proximal colon is very similar, although some labelled neurons are found throughout the length of the IMN and also in the inferior mesenteric ganglion (IMG). The middle colon is primarily supplied by the IMN and the IMG, although this region receives innervation from all the ganglia and nerves investigated, including the major pelvic ganglia (MPG). Neurons located in the distal two-thirds on the IMN and more caudal structures were labelled from the distal colon. The distal colon is the only region of gut to receive a relatively large innervation from the MPG, with approximately one third of labelled neurons in each of the IMN, IMG and the MPG. These studies also compared two retrograde tracers, Fast Blue and Fluorogold. Fluorogold was found specifically to label neurons projecting to each region of intestine injected. However, when injected into the middle colon, Fast Blue labelled neurons that project to this region as well as many neurons that Fluorogold studies indicate project to other regions; Fast Blue should therefore be used only with caution.

Origins of sympathetic innervation to the mesenteric vein vessel in cats

Physiological and histochemical studies have clearly demonstrated the control and innervation of the sympathetic nerve on the splanchnic veins. However, the origins of postganglionic fibers remain to be determined. In this study, we used the retrograde transport of horseradish peroxidase (HRP) technique to trace the origins of postganglionic neurons in pre- and paravertebral sympathetic ganglia that innervate the mesenteric vein. A segment (6-8 mm) of mesenteric vein close to the duodeno-jejunal junction was isolated. HRP was applied externally on the vein segment to allow uptake into the nerve endings. In 10 cats, there was a total of 9275 HRP-labeled neurons in the pre- and paravertebral ganglia. The neuron distribution (mean +/- S.E.M.) was as follows: 452 +/- 77 (49%) in the superior mesenteric ganglion (SMG), 248 +/- 62 (27%) in the right celiac ganglion (RCG), 111 +/- 23 (12%) in the left celiac ganglion (LCG) and 58 +/- 16 (6%) in the splanchnic ganglia. Although the appearance of HRP neurons in the paravertebral ganglia (T10-L3) was relatively sparse, there were still significant numbers in L1 (26 +/- 13, 3%), T13 (15 +/- 5, 2%) and other ganglia. The results indicate that more than 90% of the presynaptic sympathetic neurons innervating the mesenteric vein make their synaptic connections in the prevertebral ganglia, mostly SMG and then RCG as well as LCG. Postsynaptic neurons arising directly from the paravertebral ganglia (mostly L1 and T13) constitute to about 6% of the total.

Distributions of neuropeptide Y, vasoactive intestinal peptide and somatostatin in populations of postganglionic neurons innervating the rat kidney, spleen and intestine

Some peripheral peptidergic nerves selectively innervate different types of tissue in abdominal organs. Neuropeptide Y- and vasoactive intestinal peptide-immunoreactive nerve terminals have been identified in the kidney, spleen and intestine and these peptides may have important physiological actions. Somatostatin has been found in sympathetic ganglia, and nerve terminals containing this peptide have been identified in the intestine. We have used fluorescent retrograde tracers to identify renal, splenic and mesenteric postganglionic neurons in rat sympathetic ganglia and then used immunocytochemistry to determine the proportions of these three identified groups of neurons displaying immunoreactivity for neuropeptide Y, vasoactive intestinal peptide and somatostatin. Most renal, splenic and mesenteric neurons were immunoreactive for neuropeptide Y and less than 1% of cells innervating these organs were immunoreactive for vasoactive intestinal peptide. Somatostatin immunoreactivity was present only in a small percentage of mesenteric neurons and not in renal or splenic neurons. The present study demonstrates that (i) the rat kidney, spleen and intestine do not differ in the proportion of innervation by neuropeptide Y-immunoreactive neurons, (ii) the solar plexus, splanchnic ganglion and chain ganglia (T12 and T13) provide very little vasoactive intestinal peptide-immunoreactive inputs to these organs, and (iii) somatostatin-immunoreactive neurons innervate the intestine but not the kidney or spleen.

TTX-sensitive Na+ channels and Ca2+ channels of the L- and N-type underlie the inward current in acutely dispersed coeliac-mesenteric ganglia neurons of adult rats

Inward membrane currents of sympathetic neurons acutely dispersed from coeliac-superior mesenteric ganglia (C-SMG) of adult rats were characterized using the whole-cell variant of the patch-clamp technique. Current-clamp studies indicated that C-SMG neurons retained electrical properties similar to intact ganglia. Voltage-clamp studies designed to isolate Na+ currents revealed that tetrodotoxin (TTX, 1 microM) completely inhibited the large transient inward current. Half activation potential (Vh) and slope factor (K) were -26.8 mV and 6.1 mV, respectively. Inactivation parameters for Vh and K were -65 mV and 8.2 mV, respectively. Voltage-clamp studies also revealed a high-voltage-activated sustained inward Ca2+ current which was blocked by the removal of external Ca2+ or the presence of Cd2+ (0.1 mM). The dihydropyridine agonist, (+)202-791 (1 microM), caused a small increase (20%) in the amplitude of the Ca2+ current at more negative potentials and markedly prolonged the tail currents. omega-Conotoxin GIVA (omega, CgTX, 15 microM) caused a 66% inhibition of the high-voltage-activated Ca2+ current amplitude. Norepinephrine (1 microM) caused a 49% reduction in the peak Ca2+ current. This study is the first demonstration that dispersed C-SMG neurons from adult rats retain electrical characteristics similar to intact ganglia. A TTX-sensitive Na+ current as well as a high voltage-activated sustained Ca2+ current underlie the inward current in C-SMG neurons. The macroscopic Ca2+ current is composed of a small dihydropyridine-sensitive (L-type current) and a large omega-CgTx-sensitive (N-type current) component.(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.

Distribution of peptidergic terminals of enteric origin in the rat celiac ganglion

We examined the distribution of enterofugal nerve terminals of bombesin-, cholecystokinin- and vasoactive intestinal polypeptide-like immunoreactivity in the rat celiac-superior mesenteric ganglion complex. The majority of these nerve terminals were concentrated in the mesenteric side of the ganglion. The present findings suggest that some functional specialization occurs in the celiac ganglion of the rat.

False-positive artifacts of tracer strategies distort autonomic connectivity maps

The widespread use of new axonal transport tracing techniques in the ANS has resulted in substantially revised and amended descriptions of ANS organization. The present review suggests, however, that at least some of the results on which proposed revisions of ANS anatomy have been based have incorporated artifacts and therefore should be cautiously interpreted. The peripheral nervous system and viscera are composed in part of connective and endothelial tissues that are porous or 'leaky' to solutes with appropriate chemical characteristics, including the major tracer compounds. As a result, several extra-axonal routes for redistribution of label from the application site into other tissues are present. These include (1) diffusion through tissue membranes to enter directly adjacent tissues and (2) leakage into extracellular fluids within the body cavity, vasculature, lymphatics, exocrine ducts, or organ lumens to migrate to more distant tissues. As a consequence of the extreme sensitivity of the methods used, such redistribution of even minute amounts of label can produce false positives. Review of autonomic neuroanatomy suggests additional mechanisms, including tracer uptake by fibers of passage, can produce artifactual staining. Based on these surveys of tissue composition, tracer characteristics and sources of artifact, experimental controls and criteria for identifying and avoiding labeling artifacts are described. Since no single procedure is foolproof for ANS experimentation, the routine application of multiple controls, particularly ones which restrict or prevent tracer diffusion, are needed.

The origin and distribution of 5-hydroxytryptamine-like immunoreactive nerve fibres to major mesenteric blood vessels of the rat

5-Hydroxytryptamine-like immunoreactive nerve plexuses were demonstrated by indirect immunofluorescence histochemistry in whole-mount preparations and cryostat sections of blood vessels from the mesenteric vasculature of the adult rat. The major veins showed a density of innervation greater than that of the accompanying arteries. Removal of the coeliac-superior mesenteric ganglion complex resulted in almost total loss of 5-hydroxytryptamine-like immunoreactive nerves from superior mesenteric blood vessels. The results of crush lesions applied to distal vessels of the superior mesentery indicate that there were no 5-hydroxytryptamine-like immunoreactive nerve fibres extending from the enteric nervous system to these vessels. The administration of 6-hydroxydopamine resulted in a large reduction in the noradrenergic innervation, accompanied by a similar fall in the number of 5-hydroxytryptamine-like immunoreactive nerve fibres. It is suggested that the cell bodies of the 5-hydroxytryptamine-like immunoreactive nerve fibres demonstrated in the superior mesenteric vasculature are located within the sympathetic ganglia which supply the noradrenergic innervation to the same region and that the 5-hydroxytryptamine-like immunoreactivity may be co-localized with noradrenaline within sympathetic nerve fibres.

Integration of gut function by sympathetic reflexes

1. The spinal sympathetic outflow that innervates the gastrointestinal tract, including its blood vessels, has an impressive representation quantitatively, yet little is known about the functions of this system and its peripheral or central organization. Electrical stimulation or section of the splanchnic nerves have variable effects on the GI tract and does not, therefore, lead to a deeper understanding of the system. 2. The targets of the sympathetic supply of the GI tract are blood vessels, nonvascular (sphincteric) smooth musculature, myenteric neurones, submucous neurones and gut associated lymphoid tissues. The corresponding functions associated with these targets are regulation of blood flow (particularly through the mucosa) and resistance to flow, of motility, of secretion and absorption and of immune responses. Little is known about the effects of the sympathetic nervous system on the latter function. 3. The sympathetic postganglionic neurones are (at least in the guinea-pig) neurochemically characterized with respect to the targets. Neurones projecting to blood vessels contain neuropeptide Y in addition to noradrenaline, while neurones projecting to the submucous plexus contain somatostatin. No neuropeptide has been detected to date in neurones projecting to the myenteric plexus. 4. Transmission through guinea-pig prevertebral ganglia in vitro have been studied electrophysiologically. The following functions have been demonstrated: (a) transmission and distribution of preganglionic impulse activity to the targets in a relay-like fashion; (b) mediation of peripheral intestinointestinal reflexes between different sections of the GI tract; (c) integration of activity from the spinal cord and from various peripheral sources. The first function may apply particularly to the sympathetic pathway innervating blood vessels. Whether the second function occurs in vivo is questionable. The third function is the most important one for pathways involved in the regulation of motility and probably secretion and absorption. 5. Only limited information is available on preganglionic neurones projecting to prevertebral ganglia. Neurones regulating blood vessels are probably located in the intermediolateral cell column, and non-vascular visceral preganglionic neurones are situated medial to this cell column in the intermediate zone of the spinal cord. Vascular (vasoconstrictor) neurones exhibit a reflex pattern which is largely dependent on the brain stem. Spinal cord transection rostral to the sympathetic outflow causes an immediate abolition of basal and reflex activity in these neurones.(ABSTRACT TRUNCATED AT 400 WORDS)