Calcium channel currents recorded from isolated myocytes of rat basilar artery are stretch sensitive

1. Conventional and perforated patch whole-cell methods were used to measure Ca2+ channel currents from isolated rat basilar arterial myocytes in response to voltage steps. Peak currents measured in response to repeated steps to +2 mV increased over the first 3 min after gaining whole-cell access. The increase followed an exponential time course, was not due to decrease in underlying outward current and was independent of the presence of ATP and GTP in the pipette filling solution. 2. Application of positive and negative pressure to the pipette resulted in significant increase and decrease in peak inward current, respectively. Membrane stretch, associated with changes in cell volume, rather than applied pressure per se appeared to determine changes in peak current. 3. Using amphotericin B perforated patch recording, changes in cell volume on application of 80% hypo- or 120% hyperosmotic superfusing solutions were found to effect similarly peak inward current. Hyposmotically induced cell swelling increased and hyperosmotic cell shrinkage decreased peak inward current at all test potentials studied. 4. The increase in inward current in response to hyposmotic superfusate was reversible and appears to reflect an increase in voltage-dependent Ca2+ channel current since it was not due to a change in non-voltage-sensitive conductance(s) and it was as sensitive as the control current to the dihydropyridine (DHP) antagonist (-)202-791.