Expression of P2X₃ receptor in the trigeminal sensory nuclei of the rat

Abstract

Trigeminal primary afferents expressing P2X(3) receptor are involved in the transmission of orofacial nociceptive information. However, little is known about their central projection pattern and ultrastructural features within the trigeminal brainstem sensory nuclei (TBSN). Here we use multiple immunofluorescence and electron microscopy to characterize the P2X(3)-immunopositive (+) neurons in the trigeminal ganglion and describe the distribution and synaptic organization of their central terminals within the rat TBSN, including nuclei principalis (Vp), oralis (Vo), interpolaris (Vi), and caudalis (Vc). In the trigeminal ganglion, P2X(3) immunoreactivity was mainly in small and medium-sized somata, but also frequently in large somata. Although most P2X(3) (+) somata costained for the nonpeptidergic marker IB4, few costained for the peptidergic marker substance P. Most P2X(3) (+) fibers in the sensory root of trigeminal ganglion (92.9%) were unmyelinated, whereas the rest were small myelinated. In the TBSN, P2X(3) immunoreactivity was dispersed in the rostral TBSN but was dense in the superficial laminae of Vc, especially in the inner lamina II. The P2X(3) (+) terminals contained numerous clear, round vesicles and sparse large, dense-core vesicles. Typically, they were presynaptic to one or two dendritic shafts and also frequently postsynaptic to axonal endings, containing pleomorphic vesicles. Such P2X(3) (+) terminals, showing glomerular shape and complex synaptic relationships, and those exhibiting axoaxonic contacts, were more frequently seen in Vp than in any other TBSN. These results suggest that orofacial nociceptive information may be transmitted via P2X(3) (+) afferents to all TBSN and that it may be processed differently in different TBSN.

Enzymatic conversion of ATP to adenosine contributes to ATP-induced inhibition of glutamate release in rat medullary dorsal horn neurons

“…Therefore, it was rather unexpected that, in our study, ATP reduced rather than enhanced glutamate release from primary afferents onto medullary dorsal horn neurons, and that ab-me-ATP had no facilitatory effect on glutamatergic EPSCs. This is because multiple types of P2X receptors, especially P2X 3 receptors, are expressed on nociceptive TG neurons and their afferent fibers (Collo et al, 1996;Xiang et al, 1998;Kim et al, 2008). Lack of facilitatory effect of ATP on glutamate release might be due to the fast desensitization of P2X 3 receptors, such that slow bath application of ATP might desensitize P2X 3 receptors prior to their full activation (Piper and Docherty, 2000).…”

“…Although all P2X receptor subtypes except P2X 7 are expressed on TG neurons (Xiang et al, 1998), P2X 3 receptors are predominantly localized on small nociceptive TG neurons as well as primary afferent fibers (Chen et al, 1995;Xiang et al, 1998;Kim et al, 2008). Therefore, we examined the effect of ab-me-ATP, a selective P2X 1 , P2X 3 , and heteromeric P2X 2/3 receptor agonist, on glutamatergic EPSCs (Ralevic and Burnstock, 1998).…”

L’odontoblaste

“…L'ATP extracellulaire pourrait également agir comme une molécule de signalisation, en activant le récepteur purinergique P2X 3 [26]. En effet, P2X 3 est exprimé dans les fibres trigéminales de type C [27,28], et a été récemment identifié au sein des afférences nerveuses se projetant dans la couche odontoblastique [10]. Ainsi, l'ATP libéré au travers de la pannexine-3, canal mécanosensible présent sur la membrane odontoblastique [10,29], pourrait agir sur les fibres nerveuses nociceptives via P2X 3 .…”

Expression of Metabotropic Glutamate Receptor mGluR5 in Human Dental Pulp

“…Preembedding immunohistochemical staining was performed according to a procedure described elsewhere in detail (13,14). In brief, cryoprotected sections were frozen on dry ice for 20 minutes and thawed in PBS to enhance penetration and pretreated with 1% sodium borohydride for 30 minutes to remove glutaraldehyde.…”