Maternal deprivation

The effects of cocaine exposure and maternal deprivation on subsequent voluntary ingestion of cocaine and amphetamine was investigated in 7-day-old rat pups in order to further our understanding on the development of drug addiction. Maternally deprived and non-deprived pups were pre-exposed to a cocaine solution masked with 5% orange Tang solution. Four hours later, experimental pups were tested for subsequent cocaine self-administration (SA) (Exp. 1) or amphetamine SA, (Exp. 2), following a second deprivation period. Control pups were not deprived during this interval. Pups in both experiments were assessed for dose self-administered and for general activity. Results indicate that cocaine pre-exposure increased cocaine and amphetamine SA, and activity significantly increased after pre-exposure and testing sessions. Lastly, sensitization of the motor effects of cocaine was observed in pups pre-exposed to cocaine. This study provides a potential drug SA animal model not yet investigated in developing animals.

This paradigm evaluated a novel chronic stressor paradigm that could be as effective as 24 hr of maternal deprivation (24-MD), yet be intrinsically capable of examination over numerous days in pre-weanling pups. It was hypothesized that a 19 hr chronic variable stressor paradigm (19-CVS) would be equally or more effective in eliciting a corticosterone (CORT) response than 24-MD and that 19-CVS would have elevated recovery CORT levels over 24-MD. The results indicated that (1) 19-CVS elicited a significantly greater CORT response than 24-MD immediately after stressor exposure and (2) 19-CVS had significantly elevated recovery CORT in comparison to 24-MD. These results demonstrate that 19-CVS early in development is capable of robustly activating the hypothalamic-pituitary-adrenal (HPA)-axis immediately after exposure and may prove useful as an early life stressor. However, additional work is necessary to clarify how these two distinct stressors differ in termination of their respective HPA response.