The effect of intracerebroventricularly administered octopamine, phenylethylamine and epinephrine on the central serotonergic system of the rat.

Octopamine (OCT, 50-250 micrograms) and epinephrine (EPI, 10-100 micrograms) given intracerebroventricularly (icvtr) antagonized the head twitch response induced in the rat by 5-hydroxytryptophan or 5-methoxytryptamine, and hyperthermia induced by quipazine in rats kept at high ambient temperature. Phenylethylamine [PEA, 10-100 micrograms] did not change the action of serotonergic stimulants. OCT, PEA and EPI significantly depressed the cerebral level of serotonin [5-HT], and OCT also reduced the concentration of 5-hydroxyindoleacetic acid. OCT depressed, while EPI slightly accelerated the 5-HT turnover rate; PEA practically did not affect the turnover. The results indicate that OCT and EPI given icvtr to rats antagonize the central serotonergic system.