Role of P2Y receptors in trigeminal pain signalling

Migraine is a chronic neurovascular disorder associated to activation and sensitization of the trigeminovascular system. Since little information is available on purinergic transmission in the generation of migraine pain, we aimed at studying the expression and function of P2 receptors in trigeminal ganglia (TG), with particular focus on P2Y receptors. We chose an in vitro model of mixed primary TG cultures from P11 C57 black/6 mice. To study P2 receptor expression, RT-PCR and immunocytochemistry analysis were utilized, while receptor function was evaluated by single cell calcium imaging. Comparison with intact ganglion showed that cultured neurons retain, at least in part, their physical relationships with satellite glia. RT-PCR indicated expression of P2X2/P2X3 subtypes and of all cloned P2Y-receptors. Single cell calcium imaging revealed the presence of functional neuronal P2X3, as well as of ADP-sensitive P2Y1,12,13 and UTP-activated P2Y2/P2Y4 receptors on both neurons and glia. Glial cells also responded to UDP, suggesting the presence of functional P2Y6 receptors. Exposure to the pro-algogenic agent bradykinin (BK) modified neuronal P2X3 receptor function in a biphasic way, with sensitization after an acute exposure followed by a reduction of P2X3-mediated calcium responses upon chronic application. Interestingly, the function of P2Y receptors in SGCs was significantly enhanced by chronic exposure to BK, suggesting that a complex crosstalk between the two systems may exist. Thus, TG cultures represent a reliable model to study purinergic receptors signaling after acute or chronic algogens application, and P2Y receptors might represent new interesting pharmacological target for migraine pain therapy. Sponsored by the Italian Telethon Grant #GGP07032