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 approximately 12 pS at -80 mV, were activated only when ATP was present in the bath, and could be blocked by the P2-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 P2X 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 P2X receptor in sympathetic neurons.
Cloues
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Department of Pharmacology, University College London, United Kingdom.
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000320:Adrenergic Fibers / Q000502:physiology*; D000818:Animals; D009474:Neurons / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D013498:Suramin / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology*
D013498:Suramin; D000255:Adenosine Triphosphate; D015032:Zinc