ANALYSIS OF THE CEREBROVASCULAR EFFECTS OF 5-HYDROXYTRYPTAMINE IN UNANESTHETIZED GOATS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 216  (3) , 599-603
Abstract
The effects of 5-hydroxytryptamine (5-HT, serotonin) on cerebral blood flow were evaluated in unanesthetized goats under normal conditions and after selective blockade of 5-HT receptors or impairment of the sympathetic activity present in cerebral vessels. Small doses of 5-HT (0.1-9 .mu.g) injected directly into the internal maxillary artery produced dose-dependent reductions in cerebral blood flow, a decrease of 49.8 .+-. 2.5% (SEM [standard error of the mean]) occurring with the highest dose. Slow i.v. infusion of LSD (0.2-0.4 .mu.g/kg per min) methysergide or cyproheptadine (2-5 .mu.g/kg per min) partially abolished the cerebral vasoconstriction produced by 5-HT. Phentolamine and reserpine also diminished the vasoconstriction induced by 5-HT. Goats in which the superior cervical sympathetic ganglion had been removed 7-20 days before the experiment showed a significant decrease in the cerebral vasoconstriction elicited by 5-HT. 5-HT produces marked reduction in cerebral blood flow by direct excitatory effect on tryptaminergic receptors together with an indirect effect mediated by the uptake of 5-HT into the sympathetic nerve endings and the release of norepinephrine.

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