Fig.7.

Adenosine inhibits the frequency but not the amplitude of miniature EPSCs. mEPSCs were recorded in hypocretin/orexin neurons held at −60mV under voltage clamp in the presence of bicuculline and TTX in all solutions. A-C, after a stable recording of mEPSCs was obtained, adenosine (100 μM) was applied to the recorded neuron via bath solution. Sample traces of mEPSCs recorded at various stages of our experiments are shown in A and the time course of a typical experiment is presented in B. The filled bar above the trace in B indicates the application of adenosine. C, pooled data of frequency of mEPSCs from all tested neurons indicate that the frequency of mEPSCs significantly declines in the presence of adenosine and recovers after its withdrawal (**, P<0.01, ANOVA). D, accumulative probability curves for the amplitude of mEPSC events detected before and during application of adenosine are generated and plotted. There is no significant difference between events in control and adenosine groups as indicated by the Kolmogorov-Smirnov test. Solid line: control, 2770 events; dotted line: plus adenosine, 1937 events. E-F, the effect of adenosine on the frequency and amplitude of mEPSCs was examined in the presence of DPCPX, a selective A1 receptor antagonist. Adenosine does not inhibit the frequency and amplitude of mEPSCs in the presence of DPCPX as suggested by ANOVA (P>0.05, E) and the Kolmogorov-Smirnov test (P>0.05, F). In F, solid line: control, 1228 events; dotted line: plus adenosine, 1170 events. G-H, experiments were performed as described above in the presence of A2 receptor antagonists (SCH 58261 and MRS 1706). In their presence, adenosine significantly depresses the frequency (G, **, P<0.01, ANOVA) but not the amplitude of mEPSCs (H, P>0.05, Kolmogorov-Smirnov test). In H, solid line: control, 1450 events; dotted line: plus adenosine, 974 events.