Effects of psychoactive drugs on the metabolism of intracisternally administered serotonin in rat brain

Abstract

The effects of various psychoactive drugs on the metabolism of radioactive serotonin administered intracistemally were examined in rat brain. More radioactive serotonin was retained in the brains of rats anesthetized with pentobarbital during the intracisternal injection than in rats anesthetized with ether. Prior treatment with pargyline increased levels of intracistemally administered serotonin- 3H and decreased its deaminated metabolites, whereas reserpine decreased levels of serotonin- 3H. Imipramine, but not desmethylimipramine, slowed the disappearance of radioactive serotonin from brain. Chlorpromazine increased, whereas LSD decreased, the levels of radioactive deaminated metabolites of previously injected serotonin- 14C in brain. When lithium chloride was administered after the intracistemal injection of serotonin- 14C, levels of radioactive serotonin and deaminated metabolites in brain were increased above control values. The findings are discussed in relation to studies of the actions of these drugs on the metabolism of endogenous serotonin in brain, and to previous studies of the effects of these drugs on the metabolism of intracistemally administered norepinephrine.