Effect on temperature of 5‐hydroxytryptamine injected into the cerebral ventricles of cats

Abstract

In unanesthetized cats the effect on rectal temperature of 5-HT injected through a Collison cannula chronically implanted into the left lateral ventricle was examined. The response depended on the dose and the solvent employed. An intra-ventricular injection of 200 [mu]g 5-HT creatinine sulfate dissolved in 0.9% NaCl solution resulted in a long-lasting rise often interrupted initially by a transient fall in temperature. This fall became more prominent with larger doses of 5-HT, more so when the 5-HT was dissolved in distilled water, attenuating the hyperthermic effect. Intraventricular 5-HT raises rectal temperature in cats when the amount is not too large; a hypothermic effect results from paralysis of cells in the anterior hypo-thalamus which are excited by small doses, similar to the action of acetylcholine in the perfused superior cervical ganglion of the cat, where small doses excite but large doses paralyze the ganglion cells. An intraventricular injection of distilled water produced a steady rise in temperature which is attributed to release of 5-HT.