Figure 5. Effect of external Ca²⁺ on the quinine-induced current response.

A, responses of an outside-out patch membrane held at -64 mV to a 2 s puff application of 3 mM quinine. The three records were obtained in sequence; first in solution (115 mM NaCl and 2.5 mM KCl) containing 1.8 mM Ca²⁺, second in Ca²⁺-free solution, and third upon return to the first solution containing 1.8 mM Ca²⁺. Histograms to the right of each current trace were made from 2000 points of the 2 s data. B, histogram showing the effect of external Ca²⁺ on the quinine-activated unitary current amplitude, calculated from Gaussian distributions fitted to the current amplitude histograms shown in A. Error bars indicate s.d.