Ultrastructural localization of P2X3receptors in rat sensory neurons

Abstract

We used isolated IgG antibodies selective for P2X3 receptors to study the ultrastructural distribution of these receptors in rat sensory neurons. In trigeminal ganglia, P2X3 receptor immunoreactivity occurred in small and large nerve cell bodies and their processes. Endoplasmic reticulum and Golgi apparatus were heavily stained; cytoplasmic matrix was faintly to moderately stained. In synaptic glomeruli in lamina II of cervical dorsal horn, P2X3 receptor-immunoreactive core terminals were postsynaptic to unlabelled vesicle-containing dendrites and axons. In the nucleus of the solitary tract, receptor-positive boutons synapsed on dendrites and cell bodies and had complex synaptic relationships with other axon terminals and vesiculated dendrites. These observations identify sites from which ATP could be released to influence sensory signalling within the central nervous system.

Localization of P2X2 and P2X3 receptors in rat trigeminal ganglion neurons

“…It is also noteworthy that 52 % of neurons that projected to the dura were immunoreactive for one or both P2X receptors. The afferent innervation of the dura is primarily by C fibres innervating dural blood vessels that may be nociceptive and involved in the pain of migraine (Moskowitz, 1984;Strassman et al, 1996;Messlinger and Ellrich, 2001;Goadsby, 2005).Our observations that P2X 3 receptor immunoreactivity was predominantly in medium as well as small-sized trigeminal ganglion neurons is consistent with the few earlier reports in the trigeminal ganglion (Eriksson et al, 1998;Llewellyn-Smith and Burnstock, 1998;Jiang and Gu, 2002;Ruan and Burnstock, 2003;Ruan et al, 2004;Ambalavanar et al, 2005;Shinoda et al, 2005). In addition, we found that 64 % of P2X 3 receptor-expressing trigeminal ganglion neurons also express IB4, suggesting that they are mainly non-peptidergic, unmyelinated afferents, since IB4 labelling is almost entirely limited to non-peptide unmyelinated afferents in the rat (Ambalavanar and Morris, 1993;Kitchener et al, 1993;Kitchener et al, 1994;Stucky and Lewin, 1999;Gerke and Plenderleith, 2001).…”

ATP as a presynaptic modulator

“…It will also be necessary to exclude adenosine (A 1 , A 2A and the still ill-defined A 3 ) receptor involvement [29], and to use biochemical analysis to support a presynaptic localisation of P2 receptors using radioligands [e.g. 88] and immunological approaches [79][80][81][82][83][84][85][86], mainly using electron microscopy immunocytochemistry [82,84,86]. It will also be important to test whether the presynaptic role of ATP is indeed mediated by P2-receptor activation, or whether ATP is mostly acting as a phosphate donor for ecto-protein kinase modification of presynaptic proteins involved in the control of neurotransmitter release [see 158] (Figure 1).…”

“…Immunocytochemical studies show a widespread distribution of P2X 4 [79] and P2X 2 receptors in the brain [80,81], located both pre-and post-synaptically [82]. P2X 1 receptors have a more restricted location, being present in the perikarya of a distinct subpopulation of rat brainstem neurons [83] and in the cerebellum [84], and P2X 3 receptors appear only in central terminals of sensory neurons [85] and in the nucleus tractus solitarius [86]. Autoradiographic and membrane binding studies with [ [76,88,90,91].…”

Expression of P2X3and its colocalization with trpv1 in the human dental pulp

“…This effect may be exaggerated under conditions of inflammation 6,7) . Many previous studies showed the expression of P2X3 in the central and peripheral neurons 1,4,[8][9][10] . In the orofacial region, it has been reported that P2X3 immunoreactivity exists in dental pulp 3) , taste bud 8) , and temporomandibular joint 11) of the rat.…”