Effects of Endotoxin on Monoamine Metabolism in the Rat

Abstract

Summary

We have examined the effects of administered endotoxin on catecholamine metabolism in rat brain, sympathetic neurons, and adrenal medulla. Intraperitoneal endotoxin (1-5 mg) produced a dosedependent depletion of splenic and cardiac norepinephrine and of adrenal epinephrine; it also accelerated the disappearance of ³H-norepinephrine taken up from circulation. Pretreatment of animals with intraperitoneal endotoxin increased initial uptake of circulating ³H-norepinephrine into heart and spleen. Endotoxin given intraperitoneally (2.5-5 mg) or intracisternally (50-200 μg) depleted brain norepinephrine; it accelerated ³H-norepinephrine turnover in the rat brains in which norepinephrine had been radioisotopically labeled by intracisternal injection. Brain serotonin content was not affected by endotoxin. The acceleration of ³H-norepinephrine turnover in brainstem and hypothalamus after endotoxin administration preceded the induction of hypothermia. This suggests that the effects of endotoxin on body temperature may be mediated in part by central noradrenergic neurons.

The work was supported by grants from the U.S. Public Health Service (AM-11237 and HE-02014), and the National Aeronautics and Space Administration (NGR-22-009-627), and by a contract from the Office of the Surgeon General, United States Army.