Distribution of immunoreactivity for the NK1 receptor on different subpopulations of sympathetic preganglionic neurons in the rat

Abstract

The distribution of immunoreactivity to the receptor for substance P, the neurokinin 1 (NK1) receptor, was examined in preganglionic sympathetic neurons of the rat by using immunohistochemistry and retrograde neuronal tracing. About one-third of all sympathetic preganglionic neurons were NK1 receptor immunoreactive, and most of the NK1 receptor-immunoreactive neurons were also nitric oxide synthase immunoreactive. The proportions of sympathetic preganglionic neurons projecting to the superior and inferior mesenteric ganglia, adrenal gland, and lumbar sympathetic chain which were NK1 receptor-immunoreactive were determined. Most (89%) of the preganglionic neurons projecting to the adrenal glands were NK1 receptor immunoreactive. Few (17%) of the preganglionic neurons projecting to the L5 sympathetic chain ganglion were immunoreactive for the receptor, while preganglionic neurons projecting to the prevertebral ganglia were NK1 receptor immunoreactive at intermediate frequencies (61-64%). Thus, substance P acting on NK1 receptors is likely to be important in the preganglionic pathways to the adrenal medulla and viscera via the prevertebral ganglia, but is unlikely to be important in pathways to the lumbar sympathetic chain. The co-localisation of the NK1 receptor with the enzyme nitric oxide synthase was also examined. The majority of NK1 receptor-immunoreactive neurons were also nitric oxide synthase immunoreactive. Thus NK1 receptors occur on preganglionic neurons over many spinal segments and in a range of preganglionic pathways, as well as in a range of combinations with nitric oxide synthase. The heterogeneity of preganglionic neurons showing NK1 receptor immunoreactivity may reflect the involvement of NK1-mediated transmission in a variety of functional pathways, most notably the preganglionic projections to the adrenal medulla and to the viscera.

Relationship of NK3 receptor- immunoreactivity to subpopulations of neurons in rat spinal cord

“…The observations in the present report are consistent with the reported absence of NK3R-ir in superior cervical or pelvic ganglia (Ding et al, 1996). Since a high proportion of preganglionic neurons within the dorsal commissural nucleus of spinal segments L1-2 express NK1 receptors (Grkovic and Anderson, 1996), the effects of tachykinins on the function of pelvic viscera are likely to be mediated directly by NK1 receptors, and indirectly by NK3 receptors.…”

“…The dorsal commissural nucleus of spinal segments L1-2 contains preganglionic sympathetic neurons that project to the pelvic and inferior mesenteric ganglia (Strack et al, 1988;Hosoya et al, 1994, Grkovic andAnderson, 1996). Because NK3R-immunoreactive neurons near the central canal were especially numerous within segments L1-2 relative to the other segments examined (C7, T11-12, and L4-6), it is likely that NK3 receptors participate in pathways involved in the central regulation of pelvic viscera.…”

Tachykinins and tachykinin receptors: effects in the genitourinary tract

“…Autonomic ganglia supplying the male reproductive tract NK 1 receptors are present in a majority of autonomic ganglia (Grkovic and Anderson, 1996), but many of the latter do not receive a dense supply of SP-immunoreactive nerves (Messenger et al, 1999). However, collaterals of TK-immunoreactive nerves supply the autonomic prevertebral ganglia innervating the pelvic viscera and parasympathetic ganglia, including the anterior pelvic ganglion in the male guinea-pig (Mitchell, 1993).…”

Chemically distinct preganglionic inputs to iris-projecting postganglionic neurons in the rat: A light and electron microscopic study

“…1D). The calcium-binding protein calbindin has also been reported to be present in preganglionic nerve terminals surrounding many postganglionic neurons in the rat superior cervical ganglion (Anderson and Grkovic, 1996). Calbindin immunoreactivity in nerve terminals was never colocalised with CGRP immunoreactivity, nor were calbindin-IR terminals found to surround Fast Blue-labelled neurons, although a small number (11%) of Fast Bluelabelled neurons themselves were found to contain calbindin immunoreactivity.…”