The hypothalamic suprachiasmatic nuclei (SCN), the circadian master clock in mammals, releases ATP in a rhythm, but the role of extracellular ATP in the SCN was unknown. In this study, we examined the expression and function of ATP-gated P2X receptors in the SCN neurons of slices using quantitative RT-PCR and electrophysiological patch clamp recording. Our investigations showed that among the P2X receptor subunits, the P2X2 > P2X7 > P2X4 mRNAs were the most abundant. Whole-cell patch-clamp recordings revealed that ATP activates presynaptic P2X2 receptors to stimulate GABA release and inhibitory synaptic transmission. These results showed for the first time that extracellular ATP together with its receptors comprise a new excitatory system that may be involved in the regulation of the electrical activity of circadian pacemaker neurons.

Bhattacharya A, Vavra V, Svobodova I, Bendova Z, Vereb G, Zemkova H: Potentiation of inhibitory synaptic transmission by extracellular ATP in rat suprachiasmatic nuclei.