Effects of intrahippocampal injection of chemicals on the levels of plasma corticosterone in rats

Abstract The possibility that the hippocampus can influence the function of the hypothalamo-pituitary-adrenal axis was examined by injecting small quantities of various neurotransmitter substances into this brain structure. Injections of either noradrenaline or 5-hydroxytryptamine into the dorsal hippocampus had no effect on plasma concentrations of corticosterone (B). An injection of carbachol into the dorsal hippocampus elicited a significant rise in B concentrations, while that of hemicholinium into the same brain structure resulted in an inhibition of noise-induced rise of plasma B concentration. An injection of carbachol into the dorsal hippocampus counteracted dexamethsone-induced decrease in plasma B concentration, while that of hemicholinium enhanced it.