(1) The changes in rectal temperature produced by an injection of a bacterial
endotoxin piromen (10-40 ng in 1.0 microliter) on
somatostatin-14 (SS-14; 0.1-0.3 microgram in 1.0 microliter) into the preoptic anterior hypothalamic area were assessed and compared in control rats, in rats with hypothalamic SS depletion, and in rats with hypothalamic SS receptor blockade. (2) Intrahypothalamic injection of either
piromen or SS-14 produced a dose-related rise in rectal temperature in intact, control rats. The
fever induced by intrahypothalamic injection of
piromen or SS-14, as well as that induced by
intraperitoneal injection of
piromen, was antagonized by pretreatment of the hypothalamus with a SS-14 receptor antagonist (0.1 ng in 1.0 microliter) in rats. (3) On the other hand, intraperitoneal administration of
cysteamine (30-100 mg/kg), in addition to producing a dose-related fall in rectal temperature, also caused a dose-related fall in hypothalamic SS-levels in rats. Furthermore, the
fever induced by intrahypothalamic injection of
piromen, but not SS-14, was antagonized by depletion of hypothalamic SS levels with an intraperitoneal dose of
cysteamine (30 mg/kg). (4) The results indicate that a somatostatinergic pathway in the hypothalamus may mediate
endotoxin-induced
fever in the rat.