Fig. 1.

Increasing PCO₂ increases open probability of a small conductance channel. a Continuous record of the effects of different CO₂ concentrations on channel gating in outside-out patches from HeLa cells. Note that the effect of changing PCO₂ from the control level of 35 mmHg to the levels marked on the black bars on channel gating was rapid. Isolated patch was held at +10 mV. b Expanded traces from a demonstrating the gating of the channels in the patch. Dotted lines represent different levels of channel openings, and multiple openings are only seen at the higher levels of PCO₂. c All-points histograms obtained from the data in b and fitted with sums of Gaussian distributions to estimate P _o. d Plot of P _o vs PCO₂ (n = 5 for each point; bars are SEMs). Continuous line is drawn to the Hill equation, P _o  = 1/(1 + (45/PCO₂)²)