Rapid reacquisition of contextual fear following extinction in mice: effects of amount of extinction, acute ethanol withdrawal, and ethanol intoxication

Rationale Many studies have found that ethanol intoxication and withdrawal impair initial acquisition or extinction of learned behaviors. Rapid reconditioning following extinction is a form of post-extinction re-emergence of conditioned behavior that has not been studied for its interaction with ethanol intoxication or withdrawal. Objectives The goals of this paper were to define the parameters that allow rapid post-extinction reacquisition of fear in mice and investigate the effect of acute ethanol withdrawal and intoxication on acquisition, extinction, and post-extinction reconditioning. Methods We examined acquisition, extinction, and post-extinction reconditioning of contextual fear in male C57BL/6 mice. Acute ethanol withdrawal occurred 6h following a 4g/kg injection of 20% ethanol and acute ethanol intoxication occurred 5min following a 1.5g/kg injection of 20% ethanol. Results A weak context-shock pairing caused rapid reacquisition of conditioned freezing following moderate, but not extensive extinction. Acute ethanol intoxication impaired initial conditioning and acute ethanol withdrawal impaired rapid reacquisition after extinction, but not reconditioning or extinction itself. Conclusions These findings show that rapid reconditioning occurs following moderate but not extensive extinction in C57BL/6J mice. Additionally, acute ethanol withdrawal and intoxication may differentially affect different phases of conditioning. Results are discussed in terms of current ideas about post-extinction behavior and ethanol's effects on memory.