Fig. 9.

Cannabinoid agonists act presynaptically to inhibit neurotransmission. A, Plot of the ratio of the CVs squared (r = CV²_control/CV²_drug) versus the ratio of the EPSC amplitude (π = M_drug/M_control) shows that all the points generated in the presence of 100 nm Win 55,212-2 (solid circles) and 1 μm CP55,940 (solid triangles) lay on or below the diagonal (r = π), whereas points generated in the presence of 10 μm CNQX (open squares) lay above the diagonal. B, After scaling to the peak of control, the average EPSC of five sweeps in the presence of 100 nm Win 55,212-2 was superimposed on that of control. The current surge before the EPSC is stimulus artifact.C, Summary of successful synaptic responses during control and after application of 100 nm Win 55,212-2. In the presence of 100 nm Win 55,212-2, successful synaptic responses were reduced from 96 ± 4% (control) to 60 ± 11%,n = 10, *p < 0.01 (paired ttest).