Because norBNI and ethanol displayed comparable effects, we sought to determine the influence of KOR blockade on the ethanol-induced augmentation of IPSPs by first applying norBNI and subsequently adding ethanol in the continued presence of norBNI. Superfusion of 0.2 μM norBNI significantly increased IPSP amplitudes to 134 ± 6% of control (n = 7; F (2,6) = 16.26), and subsequent addition of 44 mM ethanol together with norBNI did not significantly affect IPSP amplitudes which remained at 131 ± 8% of control level (n = 7; Fig. 5A). Thus, norBNI completely blocked the action of ethanol. Consistent with a lack of effect of ethanol in the presence of norBNI, the norBNI-elicited decrease of the paired-pulse ratio remained unchanged from 75 ± 10% (norBNI) to 79 ± 12% of control upon application of ethanol (n = 7; F (2,6) = 4.678; not shown). Another 2 neurons that showed no response to norBNI were exposed to ethanol. Ethanol largely increased IPSPs in both neurons (157% and 165% of control; not shown).
