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.The rise in plasma norepinephrine (NE) and epinephrine (E) levels during stress has been well documented (DeTurck and Vogel, 1982; McCarty and Kopin, 1979). Considerably less is known about the effects of drugs on these stress-induced increases in biogenic amine levels. In rats, ganglionic blockade by chlorisondamine and blockade of NE release by bretylium has been shown to decrease or reverse stress-induced increases in plasma NE and/or E (McCarty and Kopin, 1979). These effects are not surprising, due to the known action of these drugs on the autonomic nervous system. However, drugs unrelated to the autonomic nervous system can also affect the biogenic amine levels during stress. Fentanyl-oxygen anesthesia reduces plasma NE and E in man during surgery (Stanley, Berman, Green and Robertson, 1980), and diazepam reduces NE levels during third molar extraction without affecting E level (Goldstein, Dionne, Sweet, Gracely, Brewer, Gregg and Keiser, 1982). Recently, we observed that ethanol can reduce stress-induced increases in rat plasma levels of both NE and E (DeTurck and Vogel, 1982). In that case, it has been speculated that this reduction is due to the sedative or anxiolytic properties of alcohol (DeTurck and Vogel, 1982). To test the possibility that these properties can indeed affect stress-induced increases in NE and E, we measured the effects of several psychoactive drugs on plasma catecholamine levels during stress. The drugs were the stimulant amphetamine, the sedative drugs morphine and pentobarbital, and the anxiolytic/sedative drugs diazepam and alprazolam.