Fig. 2.
Comparisons of the effects of depression produced by increased frequency of nerve stimulation with Ca2+ channel block by Cd2+ and the presynaptic modulator adenosine. Note that similar inhibition of release (end-plate potentials [EPPs]) is produced by similar inhibition of Ca2+ currents under three conditions. For depression produced by increasing the frequency of nerve stimulation, a frequency between 0.1 and 1 Hz was used to obtain stable EPPs that were approximately 50% of the control level. Cd2+ (10–20 µm) and adenosine (10 mm, which is a supramaximal concentration) were used for comparison with other results. The bathing solution was the same composition as that used for figure 1. For further details see text. Data for Cd2+ and adenosine were taken from the review by Silinsky,15 in which the frequency of stimulation was 0.017 Hz.