LOCALIZATION OF ATP-GATED ION CHANNELS IN CEREBELLUM USING P2X(2)R SUBUNIT-SPECIFIC ANTISERA

THE distribution of the P2x(2) purinoceptor subunit protein, which for ms ATP-gated ion channels by homo- and hetero-multimeric assembly, was examined in the adult rat and guinea-pig cerebellum using two novel a ntisera generated against separate 18 amino acid sequences located in the predicted extracellular domain of this subunit. These antisera, th e first available for labelling the P2x(2)R subunit protein, were vali dated by selective labelling of a fusion protein containing the target amino acid sequences, and in cerebellum, by peptide specific block of immunoreactivity and by comparison with the distribution of P2x(2)R m RNA. P2x(2)R-like immunoreactivity was seen in Purkinje cells, specifi cally the soma and dendrites, neurons in the granular and molecular la yers and deep cerebellar nuclei. The identification of P2x(2)R-like im munoreactivity within the cerebellar neural circuitry is consistent wi th a role for extracellular ATP acting as a fast neurotransmitter in m otor learning and coordination of movement. Additionally, labelling of neuroglia and fibre tracts supports a diverse role for extracellular ATP in CNS homeostasis.