Antagonist effects of opioid-, Orphanin FQ- and cannabinoid-induced inhibition of IBa. (a) IBa inhibition by 1 μM DAMGO in control (untreated neurons), after naloxone (opioid receptor antagonist), after [Phe1Ψ(CH2-NH)Gly2]NC(1–13)NH2 (ORL-1 receptor antagonist) and after AM281 (CB1 receptor antagonist). (b) IBa inhibition by 1 μM Orphanin FQ in control (untreated neurons), after naloxone, after [Phe1Ψ(CH2-NH)Gly2]NC(1–13)NH2 and after AM281. (c) IBa inhibition by 10 μM WIN55,212 in control (untreated neurons), after naloxone, after [Phe1Ψ(CH2-NH)Gly2]NC(1–13)NH2 and after AM281. Numbers in parentheses indicate the number of neurons tested. *P<0.05 compared with control, ANOVA.