[Effects of ketamine on pituitary-adrenal axis in rats]

We examined the effects of ketamine (20 mg.kg-1) on plasma ACTH, Comp. B, aldosterone and ir-ANP levels in unstrained rats. We divided rats into two groups, saline group as control (saline group) and ketamine group (ketamine treated rats). Plasma samples were taken before ketamine or saline infusion to determine a pre-treatment value, and samples were also taken at 15, 30, 60 minutes after the infusion. ACTH, aldosterone and ir-ANP were measured by radioimmunoassay. Comp. B was determined by a fluorometric method. We obtained the following results: 1) Plasma ACTH levels increased significantly in the ketamine group, while there was no such a marked increase in the saline group. The slight increase in ACTH in the saline group could have resulted from handling during i.v. infusion or psychic stress; 2) Plasma corticosterone and aldosterone levels increased markedly in both groups. However, the magnitude of the adrenocortical response was significantly greater than in the saline group; 3) Plasma ir-ANP showed no significant change in both groups. These results suggest that ketamine stimulated pituitary-adrenal axis, and the adrenal stimulation produced by ketamine are greater than those induced by the stress of handling or psychic stress.