Body temperature responses at different ambient temperatures following injections of prostaglandin E1 and noradrenaline into the brain.

Since prostaglandins of the E series have been implicated in the production of fever by pyrogens, we have applied them directly to the anterior-hypothalamic preoptic area of uunanesthetized rats at various ambient temperatures. In this paper we have determined accurately the region of the brain of the rat from which temperature responses can be produced by local injection. In addition we present evidence to suggest that the responses to local injections of PGE1 are relatively unaffected by environmental temperatures, whereas those in response to injections of noradrenaline are influenced by ambient temperature. These results are discussed in light of similar findings with respect to the response to pyrogens in that it is relatively unaltered by ambient temperature. This work lends further support to the hypothesis that pyrogens act in the hypothalamus by releasing prostaglandins.