PROPERTIES OF ATP-GATED CHANNELS RECORDED FROM RAT SYMPATHETIC NEURONS - VOLTAGE-DEPENDENCE AND REGULATION BY ZN2+ IONS

1. I recorded ATP-gated channels from excised outside-out patches from rat sympathetic neurons. The channels had a unitary conductance of similar to 12 pS at -80 mV. were activated only when ATP was present in the bath, and could be blocked by the P-2-purinoceptor antagonist suramin. 2. The open probability of the channels showed a strong voltage dependence, increasing significantly with hyperpolarization. This suggests that whole cell rectification of currents evoked by P-2x receptor activation is a result of channel voltage dependence and not of properties of ion permeation. 3. Low concentrations of extracellular Zn2+, which has previously been shown to potentiate whole cell ATP-evoked currents, increased the open probability of ATP-gated channels without altering the unitary conductance. 4. Zn2+ increased both the opening frequency and the burst duration of ATP-gated channels. The results are consistent with Zn2+ acting as an allosteric modulator of the P-2x receptor in sympathetic neurons.