Effects of controllability of stress on hippocampal pharmacology

To examine the effect of the controllability of stress on aspects of hippocampal noradrenergic, opiate, and cholinergic pharmacology, we trained rats in a controllability paradigm and assessed [H-3] desmethylimipramine, [H-3]quinuclidinyl benzilate, or [H-3]naloxone binding in hippocampal areas CA1, CA3, and the dentate gyrus with quantitative autoradiography. Rats that could control shock termination were yoked to rats that could not control termination of equivalent shock; a third group of rats received no shock. When the rats that could terminate shock responded at an 85% rate, their brains were removed and sectioned, incubated with tritiated Ligands, and exposed to film for an appropriate period. Quantitative densitometry revealed a 10%-22% decrease in naloxone binding in CA3 in rats receiving uncontrollable shock; no significant changes were observed in rats that could control shock. Thus, the ability to control shock prevented stress-induced changes in mu opiate receptor binding in area CA3 of the hippocampus.