Three studies were conducted to examine how absorption rate affects rapid tolerance to
ethanol-
induced hypothermia. Two procedures for administering alcohol were used to vary the rates of
ethanol absorption: a 40-min intravenous (IV) infusion and the more rapidly absorbed intraperitoneal (IP) injection. Hypothermic responses of Long-Sleep (LS), Short-Sleep (SS), and DBA/2JIbg (DBA) mice were examined. Although IV
ethanol infusions produced similar or higher blood
ethanol levels (BELs) compared to IP administration, the degree of
hypothermia was significantly greater with the more rapidly absorbed IP administration. It was concluded that the rate at which
ethanol increases in the blood influences the degree of
hypothermia: the greater the rate of blood
ethanol increase, the greater the hypothermic effect. Rapid development of tolerance to
ethanol may explain why a slow increase in BEL produces less
hypothermia than a rapid increase in BEL. The IV route provides a precise method of
drug administration for the study of acute tolerance.