Effect of different treatment regimens with ethanol and p-chlorophenylalanine on tolerance development in UChA and...

Since we have previously observed a genetic difference in the development of tolerance to the narcotic effect of ethanol in UChA and UChB rats when providing them with a 10% v/v ethanol solution as sole drinking fluid, experiments were performed in order to know whether the resistance to development of tolerance to ethanol in UChB rats was also exhibited after other regimens of ethanol administration, namely, a 2.76 g/kg ethanol IP injection 24 hr before the experiment, only 10% v/v ethanol solution as sole drinking fluid for 21 days, or receiving acutely a daily dose of 2.76 g/kg ethanol by gavage for seven days. Participation of serotoninergic neurons was tested by treating rats with p-chlorophenylalanine (p-CPA), a known serotonin depletor. Results show that UChA rats developed tolerance to ethanol-induced narcosis and hypothermia, while UChB rats developed it to narcosis only when they received acute oral doses of ethanol for 7 days and did not develop tolerance to hypothermia with any of the treatment regimens. p-CPA pretreatment did prevent the development of tolerance in both strains of rats, confirming the participation of serotoninergic neurons in ethanol tolerance in rats.