Splenic Neurons Research Articles

The inflammatory reflex: the current model should be revised

The inflammatory reflex: the current model should be revised

Localization of sympathetic and parasympathetic neurons innervating pancreas and spleen in the cat

The localization of sympathetic and parasympathetic neurons innervating the pancreas and spleen was studied in the cat utilizing retrograde transport of wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP). Injection of WGA-HRP into the pancreas resulted in retrograde labeling in the whole of the solar plexus, while injection of WGA-HRP into the spleen also resulted in heavy labeling in the celiac ganglia bilaterally. Only a few labeled neurons were distributed in the superior mesenteric ganglion. With respect to parasympathetic innervation, HRP-labeled pancreatic and splenic neurons were found throughout the rostrocaudal extent of the dorsal motor nucleus of the vagus nerve (DMV) bilaterally. Although pancreatic neurons in the DMV were mainly observed in limits rostral to the obex, splenic neurons were centered at the level of the obex.

Proportions of renal and splenic postganglionic sympathetic populations containing galanin and dopamine beta hydroxylase

Galanin is a 29-amino acid neuropeptide found in rat spinal cord, autonomic ganglia and gastrointestinal tract, as well as in other areas of the nervous system in rats and other species. As part of an overall objective to determine if peptides contribute to target-specific control of visceral function, this study was designed to determine the percentages of populations of renal and splenic postganglionic neurons that contain galanin, and to determine if these neurons were likely to be adrenergic. Retrogradely transported fluorescent dyes were placed on renal and splenic nerves in male Wistar rats anaesthetized with sodium pento-barbital. Four days post-operatively, rats were perfused transcardially with fixative, and T 12−L 1 thoracolumbar chain ganglia, splanchnic ganglia and the solar plexus were removed. Immunocytochemical methods were then used to determine the proportions of the retrogradely labelled renal and splenic neurons containing galanin-like immunoreactivity and dopamine beta hydroxylase-like immunoreactivity. In seven rats, 24 ± 3% of 2838 renal neurons were found to contain galanin-like immunoreactivity; in six rats, 32 ± 5% of 5102 splenic neurons were found to contain galanin-like immunoreactivity. These proportions of the two populations were not significantly different from one another. In three rats, 94 ± 2% of 684 renal neurons were found to contain dopamine beta hydroxylase-like immunoreactivity, and 95 ± 2% of 2597 splenic neurons in three rats also showed dopamine beta hydroxylase-like immunoreactivity. These experiments indicate that subpopulations of both renal and splenic postganglionic sympathetic neurons contain the neuropeptide galanin and that these neurons are likely to be adrenergic in function. These findings suggest a role for galanin in control of the kidney and the spleen by the sympathetic nervous system.

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.

Areas of rostral medulla providing tonic control of renal and splenic nerves

The objective of this study was to determine whether nonuniform control of tonic discharge of renal and splenic nerves by the rostral ventrolateral medulla (RVLM) is dependent on viscerotopic representation of the kidney and the spleen in this region. Small (15 nl, 13 pmol) injections of the potent tau-aminobutyric acid agonist muscimol were used to map the RVLM of anesthetized rats, searching for areas that selectively provided tonic excitation of renal or splenic nerves. Most of the muscimol microinjections produced depressor responses and inhibition of sympathetic nerve activity. Activity of renal nerves was inhibited significantly more than that of splenic nerves, but we found no evidence for topographical organization of RVLM influences on tonic activity of these two nerves. However, this investigation did yield an important new observation, since approximately 10% of the injections caused pressor responses and increases in sympathetic discharge. The unexpected increases must have been caused by blockade of small groups of tonically active sympathoinhibitory neurons located throughout the RVLM. This disinhibition was not evoked from any specific region of the RVLM. In conclusion, the RVLM neurons and putative interneurons that tonically control the discharge of postganglionic renal and splenic neurons appear to be distributed homogeneously throughout this area. Neither excitatory nor inhibitory elements were organized topographically to specifically influence the renal or the splenic nerve. The neural organization responsible for the preferential effect on renal nerves may exist in the local microcircuitry within the RVLM and will be revealed only by an even more discrete analysis of these circuits.

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 T 6-L 4, 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.

Comparison of the distributions of renal and splenic neurons in sympathetic ganglia

Postganglionic neurons in different sympathetic ganglia are innervated selectively by preganglionic neurons originating from different segments of the spinal cord. These selective connections between pre- and postganglionic neurons may determine the specificity with which postganglionic nerves participate in differential reflex reactions. Because specificity of renal and splenic nerve responses to stimulation of visceral afferent nerves may depend on the distribution of postganglionic neurons in sympathetic ganglia, retrograde axonal transport of horseradish peroxidase was employed in this study to identify the ganglionic distribution of cell bodies of postganglionic neurons supplying the kidney and spleen in cats. Superior mesenteric, left and right celiac ganglia usually are fused together into a complex ganglion (solar plexus) in the cat. Most labeled cell bodies of renal nerves were clustered in groups within the solar plexus, but some cell bodies of renal neurons were observed in upper lumbar (L1–L3) and lower thoracic (T12–T13) paravertebral sympathetic ganglia. In contrast, 90% of labeled splenic neurons were scattered randomly throughout the left and right celiac poles of the solar plexus. In conclusion, the disparate distribution of renal and splenic neurons in sympathetic ganglia provides an anatomical basis for differential reflex responses in the two populations of nerves.