We next assessed the interaction of ethanol with KOR agonists. In this set of experiments we activated KOR with dynorphin or U69 and subsequently applied ethanol in the continued presence of the ligands. Two concentrations of dynorphin (1 and 2 μM) and U69 (0.5 and 1 μM) were used to ensure that maximum effect was obtained. Superfusion of 1 μM dynorphin decreased IPSPs to 80 ± 6% of control and subsequent addition of 44 mM ethanol reversed the dynorphin effect and increased IPSP amplitude to 106 ± 7% of pre-dynorphin level (n = 5). Superfusion of 2 μM dynorphin decreased IPSPs to 78 ± 7% of control, and subsequent addition of 44 mM ethanol reversed the dynorphin effect and increased IPSP amplitude to 101 ± 10% of pre-dynorphin level (n = 5). Because results obtained with both concentrations were similar, the data from both sets of neurons were combined and showed that 1–2 μM dynorphin significantly decreased IPSPs to 79 ± 4% of control (n = 10; F (2,9) = 14.43). Addition of ethanol significantly increased IPSPs to 104 ±
