Abstract

This study investigated the effects of preexposure to ethanol, diazepam, and context on conditioned fear and extinction in Sparague-Dawley male rats. Four drug-prexposure or saline-preexposure sessions were given in the experimental chamber before fear conditioning. Fear was conditioned by pairing an experimental chamber with footshocks and conditioned fear was assessed by observing freezing. During extinction session, rats were exposed to the chamber without shocks. Diazepam 5.0mg/kg and ethanol 1.2g/kg decreased freezing response immediately following the shocks. The preexposure to the context did not influence the conditioned freezing. In the saline-preexposure group, aminals that received extinction with either ethanol or diazepam showed significantly more freezing than the saline controls during undrugged test. These results indicated that both ethanol and diazepam produce state-dependent fear extinction even though the contextual preexposure. In the ethanol-preexposure or diazepam-preexposure groups, administration of the same drug during extinction did not interfere with fear extinction. These results showed that the contextual preexposure did not reduce conditioned freezing, but the preexposure to either ethanol or diazepam reduced the drugs' interference with fear extinction. These findings are discussed that the preexposure to drugs reduced the drugs' interference with fear extinction through both the drugs' sustained ability to weaken fear conditioning with all the repeated exposure and the tolerance effect due to drug preexposure. The practical implications for the interaction effects between drug therapy and extinction are noted.