Regional metabolism of 5-hydroxytryptamine in brain under acute and chronic heat stress.

The metabolic alteration of 5-HT in four different regions of rat brain and plasma was studied under acute and chronic heat stress. A generalised elevation of 5-HT in all the brain regions along with high plasma level was observed in animals subjected to 4 hour heat stress at 38 degrees C. Such elevation of brain 5-HT may be due to entry of plasma 5-HT into the brain owing to breakdown of blood-brain barrier (BBB). In heat adapted rats, where BBB remained unaffected, no increase in brain 5-HT was observed, rather a significantly low level was maintained both in plasma and brain tissue.

Effect of restraint stress on cannabis-induced catalepsy in rats.

The effect of restraint stress (1, 2 and 4 hr) on cannabis-induced catalepsy, was investigated in rats. Restraint stress produced a time-related-potentiation of the cataleptic effect of a sub-cataleptic dose of cannabis. Stress (4 hr)-induced potentiation of cannabis catalepsy was attenuated after pretreatment of the animals with drugs known to decrease central 5-HT and prostaglandin activity, but was unaffected by metyrapone, an inhibitor of endogenous corticoid synthesis. The results suggest the involvement of 5-HT and prostaglandins in restraint stress-cannabis interaction. The results have been discussed in the light of earlier investigations, from this laboratory, indicating increased rat brain 5-HT and prostaglandin activity, following restraint stress, and possible 5-HT mediation in central effects of prostaglandins. It is suggested that restraint stress first enhances rat brain prostaglandins, which in its proposed role as the first mediator' of stress, activates the serotonergic system in this species. This prostaglandin 5-HT link, thus mediates the observed potentiating effect of restraint stress on cannabis catalepsy.