Effects on Temperature of Morphine Injected into the Preoptic/Anterior Hypothalamus,Medulla Oblongata,and Peripherally in Unrestrained and Restrained Rats 1 2

Abstract

Summary

Changes in T_re were determined in unrestrained rats after injections of morphine into the PO/AH and MED regions. Injections into the former site consistently caused hyperthermia, while medullary injections caused only inconsistent small responses. Destruction of the PO/AH region did not enhance the response to medullary injections of morphine. Restraint reversed responses to PO/AH and ip administration of morphine, resulting in hypothermia. These results provide additional evidence for the concept of a sensitive primary temperature control in the PO/AH region and a secondary control, which responds minimally to drugs, in the medulla.