[The effect of morphine on baseline alcohol motivation in rats]

Morphine was studied for its effects on the baseline alcohol motivation in experiments on ethanol-preferring (EPRs) and -rejecting (ERRs) rats. The intraperitoneal administration of morphine in doses of 0.05 and 1 mg/kg caused an increase in ethanol uptake in EPRs both during administration of morphine and after its discontinuation and did not affect the voluntary consumption of morphine solution. The above doses induced no increases in ethanol uptake in ERRs as compared with the controls and stimulated their voluntary consumption of morphine solution. It is concluded that in EPRs, alcohol motivation is enhanced by morphine and the latter used in a dose of 0.05 mg/kg may cause the withdrawal syndrome in ERRs.