Fever produced by microinjection of typhoid vaccine into hypothalamus of cats

¹ Instituto de Medicina Experimental, Universidad de Chile, Santiago, Chile, and Colgate University, Hamilton, New York

In unanesthetized cats, 1 or 2.5 µliters typhoid vaccine were injected into several areas of the hypothalamus, the lateral cerebral ventricle, and other areas of the brain. The concentrations of the pyrogen used ranged from 1/8 to 1/16,000 of the dose required to produce fever by the intravenous route. Fever was obtained in all experiments in which the vaccine was applied to the anterior hypothalamus or to the lateral cerebral ventricle. No significant rise in temperature occurred following injections into other brain areas unless extremely high doses were employed. The short latency and the rapid rise in temperature following the injection of typhoid vaccine into the anterior hypothalamus suggest that pyrogens act on the cells of this diencephalic structure when fever is produced.

Key Words: CNS site of action for pyrogens • cat hypothalamus • temperature regulation • diencephalic microinjections

Submitted on October 5, 1964

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