Figure 5.

Effects of IK_Ca blockers on the time course of the response to A23187. The records show the decreases in the transmission of light by a suspension of rabbit red cells exposed to A23187 (0.4 μM, applied at A in each record). (a), (c) and (e) are control responses for the tests shown in (b), (d) and (f) respectively. A fresh sample of cells was used on each occasion. In (b), UCL 1407 (0.3 μM) was added at the horizontal arrow, 30 s after A23187. Note the rapid and complete inhibition of the change in light transmission. In record (d), UCL 1438 (0.5 μM) was introduced at the first vertical arrow. 2.7 min later, A23187 was applied in the presence of UCL 1438. Though the initial response to A23187 was little reduced, the fall in light transmission progressively slowed and ceased after ∼1.5 min. Record (f) illustrates the inhibitory action of clotrimazole (0.2 μM, added at the first vertical arrow). In contrast to the findings with UCL 1407 and 1438, the fall in light transmission induced by A23187 (second arrow) continued throughout the recording, albeit at a reduced rate. The time and transmission calibrations apply to all the traces.