Effects of psychoactive drugs on plasma catecholamines during stress in rats.

In unstressed rats, morphine, pentobarbital, diazepam and alprazolam were without effect on plasma norepinephrine (NE) and epinephrine (E) levels. Amphetamine increased the levels of both catecholamines. In stressed rats, morphine did not affect the stress-induced increases in NE and E. Amphetamine enhanced the catecholamine stress-response further. Diazepam reduced stress-induced increases of NE levels. Pentobarbital and alprazolam attenuated stress-induced increases of both NE and E levels; this effect was particularly marked with alprazolam.