Abstract The effect of seven compounds intracellularly applied by spontaneous diffusion were investigated on the EPYLRFamide-induced reduction of acetylcholine-induced inward current (ACh-current) recorded from identified neurones from Helix lucorum. Inward currents were recorded from neurones LPa2, LPa3, RPa3 and RPa2 in isolated ganglia preparations using two-electrode voltage clamp technique. ACh was applied ionophoretically. Heparin, an antagonist of IP 3 receptors (IP 3Rs), and IP 3, the agonist of IP 3Rs, decreased the effect of EPYLRFamide. Thio-NADP, a blocker of NAADP-induced Ca 2+ release, β-NAADP, Ca 2+ releaser, R24571, W-7 (both calmodulin antagonists), and KN-62, a selective inhibitor of Ca 2+/calmodulin-dependent protein kinase II, did not change the modulatory effect of EPYLRFamide. These data suggest that EPYLRFamide decreases ACh-current through elevation of the basal intracellular level of the putative endogenous agonist of IP 3Rs which activates release of Ca 2+ from intracellular stores. It is concluded that intracellular free Ca 2+ acts on ACh receptor/ionic channel without activation of calmodulin and Ca 2+/calmodulin-dependent protein kinase II.