Figure 6.

Inosine-mediated modulation of asynchronous ACh secretion is associated with Ca²⁺ influx through P/Q-type VGCC. (A) Inosine (100 μM) reduced asynchronous ACh release induced by 12 mM K⁺ (n = 4). (B,C,D) The modulatory effect of inosine on 12 mM K⁺-evoked ACh release was not observed when preparations were pre-incubated with the universal VGCC blocker Cd²⁺ (100 μM, n = 3), 0 Ca²⁺-EGTA (n = 3) or the specific P/Q-type VGCC blocker ω-Aga (100 nM, n = 4), respectively. In (D) it is interesting to note that 100 μM inosine decreased spontaneous ACh secretion when MEPP frequency was assessed in the presence of ω-Aga and control K⁺ (5 mM), a situation not dependent on Ca²⁺ influx through P/Q-type VGCCs (n = 4, P < 0.01). Data (mean ± SEM) are expressed as percentage of control values. **P < 0.01, anova followed by Tukey's test.