P2Y1 receptor-mediated glutamate release from cultured dorsal spinal cord astrocytes

P2 receptors have been implicated in the release of neurotransmitter and proinflammatory cytokines by the response to neuroexcitatory substances in astrocytes. In the present study, we examined the mechanisms of ADP and adenosine 5'-O-2-thiodiphosphate (ADPbetaS, ADP analogue) on glutamate release from cultured dorsal spinal cord astrocytes by using confocal laser scanning microscopy and HPLC. Immunofluorescence activity showed that P2Y₁ receptor protein is expressed in cultured astrocytes. ADP and ADPbetaS-induced Ca²⁺]_i increase and glutamate release are mediated by P2Y₁ receptor. Ca²⁺ release from IP₃-sensitive calcium stores and protein kinase C (PKC) activation is important for glutamate release from astrocytes. Furthermore, P2Y₁ receptor-evoked glutamate release is regulated by volume-sensitive Cl^? channels and anion co-transporter, which open up the possibility that P2Y₁ receptor activation causes the increase of cell volume. Release of glutamate by ADPbetaS was abolished by 5-nitro-2 (3-phenyl propy lamino)–benzoate plus furosemide but was unaffected by botulinum toxin A. These observations indicate that P2Y₁ receptor-evoked glutamate may be mediated via volume-sensitive Cl^? channel but not via exocytosis of glutamate containing vesicles. We speculate that P2Y₁ receptors-evoked glutamate efflux, occurring under pathological condition, may modulate the activity of synapses in spinal cord.