The ATP responses in ciliary neurons acutely dissociated from chick ciliary ganglia were investigated using the nystatin perforated patch recording mode. ATP induced a transient inward current at a holding potential of -50 mV in a concentration-dependent manner. The half-maximum effective concentration of ATP was 8.2 μM and the Hill coefficient was 0.9. The current-voltage relationship of the ATP response revealed a strong inward rectification at potentials more positive than -30 mV and the reversal potential was near 0 mV. The relative potencies of purinoceptor agonists were in the order of ATP > 2-methylthio-ATP > ADP. Neither adenosine, AMP nor α,β-methylene-ATP induced any response. The ATP-induced inward current was blocked by suramin, a selective P2 purinoceptor antagonist, in a concentration-dependent manner. The half-maximum inhibitory concentration was 4.5 μM. The cytosolic Ca2+ concentration was increased by ATP and suramin inhibited the increase in a concentration-dependent manner. These results suggest that ATP operates non-selective cation channels by acting on P2y purinoceptors and has a role in the excitation of ciliary neurons.
ASJC Scopus subject areas