Student Research - Author: Debra Burock

Advisor: Earl Thomas

The Context-Dependent Effect of Chlordiazepoxide on Lateral Septal Activity in the Rat Brain

There is substantial evidence that suggests that the lateral septum (LS) is involved in the fear-relief process. Additionally, current research indicates that activation of the LS may be contextually dependent and influenced by the hedonic properties of the environment. This study examines the neural activity of the LS in two distinct paradigms, specifically the elevated plus maze and Pavlovian differential fear conditioning, each containing an aversive and non-aversive context. LS neurons were examined during baseline conditions across contexts and were found to have significantly lower activity in the closed arm of the plus maze, while units in the fear conditioning study had higher rates of firing in the no shock chamber.

In general, it was found that going from the closed to open arm of the plus maze increased LS firing while moving from the open to closed arm resulted in a decrease in LS activity. Additionally, when the benzodiazepine chlordiazepoxide was administered at 2, 5, and 10mg/kg doses unit activity decreased. However, due to the fact that contextual conditioning was not achieved the results to the conditioning study are inconclusive. Overall, these results suggest that firing in the LS is contextually-dependent and that the effect of CDP is relative to the paradigm employed to produce a fear response. Moreover, the finding that LS units increase in the presence of an aversive context is contradictory to the original hypothesis that unit activity would decrease in an aversive context and this suggests that animals in the plus maze may utilize an adaptation response in order to suppress fear.