Contingent tolerance to the anticonvulsant effects of alcohol

Ethanol (1.5 g/kg) administered intraperitoneally to kindled rats blocked the seizures normally elicited in these subjects by electrical stimulation of the amygdala. Tolerance to this anticonvulsant effect developed following a series of ethanol intubations delivered at 48-hr intervals only when an amygdaloid stimulation was administered during each period of ethanol intoxication. Subjects stimulated 1 hr following each intubation were tolerant to the intraperitoneal test dose after only five intubations (2 g/kg), whereas those stimulated 1 hr prior to each intubation displayed no tolerance during the course of 20 such trials. Even at high intubation doses (5 g/kg), significant levels of tolerance to the anticonvulsant effect of the intraperitoneal test dose were not observed in subjects unstimulated during each period of post-intubation intoxication. These findings emphasize the important role of response contingency in ethanol tolerance; tolerance develops readily for only those effects of alcohol that repeatedly manifest themselves during the periods of ethanol exposure.