Neurokinin-1 receptor localisation in guinea pig autonomic ganglia

Abstract

We have used multiple‐labelling immunohistochemistry and confocal microscopy to determine the distribution of immunoreactivity to the tachykinin neurokinin‐1 (NK1) receptors in guinea pig sympathetic ganglia. Although nerve fibres containing immunoreactivity to substance P were common in all ganglia except the superior cervical ganglia, most neurons expressing NK1 receptor immunoreactivity were not closely surrounded by pericellular baskets of substance P‐immunoreactive boutons. Conversely, many neurons surrounded by baskets of substance P‐immunoreactive boutons lacked NK1 immunoreactivity. In the coeliac and inferior mesenteric ganglia, NK1 receptor expression was restricted almost entirely to noradrenergic neurons that contained somatostatin immunoreactivity and projected to the enteric plexuses. In the lumbar chain and paracervical ganglia, NK1 immunoreactivity was expressed by nonnoradrenergic vasodilator neurons containing immunoreactivity to vasoactive intestinal peptide. Taken together, our results show that sympathetic neurons in different functional pathways express NK1 receptor immunoreactivity. However, the neurons that could respond to endogenously released substance P through NK1 receptors may be distant from presynaptic release sites. These observations suggest that, in sympathetic ganglia, substance P may modulate ganglionic transmission through heterosynaptic actions on NK1 receptors. J. Comp. Neurol. 412:693–704, 1999. © 1999 Wiley‐Liss, Inc.

Structure of peripheral synapses: autonomic ganglia

“…This might mean that most sensory collaterals do not form synapses with prevertebral sympathetic neurons. Indeed, most of these fibres do not appear to be closely associated with the surface of the sympathetic neurons (Messenger et al 1999;Jobling et al 2001). If this really is the case, then the slow excitatory potentials mediated by substance P after stimulation of sensory collaterals (e.g.…”

Post‐stimulus potentiation of transmission in pelvic ganglia enhances sympathetic dilatation of guinea‐pig uterine artery in vitro

“…A strong candidate for mediator of the slow depolarization is substance P. Substance P is located in preganglionic neurones projecting selectively to VIP immunoreactive vasodilator neurones in guinea‐pig paracervical ganglia (Morris & Gibbins, 1987). Furthermore, immunoreactivity for NK1 receptors has been demonstrated on a subpopulation (12%) of VIP immunoreactive neurones in paracervical ganglia (Messenger et al 1999). In the current study we found that about half of the paracervical neurones were depolarized and fired volleys of action potentials when exposed to exogenous substance P. This discrepancy in the proportion of neurones responding to substance P compared with that with NK1 receptor immunoreactivity may be due to the presence of other receptor subtypes, such as truncated NK1 receptors that do not show immunoreactivity to C‐terminally directed antisera (Baker et al 2003), or NK3 receptors (Mawe, 1995; Jobling et al 2001; Johnson & Bornstein, 2004).…”

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).…”