Prostaglandin E₂ may induce hyperthermia through EP₁ receptor in the anterior wall of the third ventricle and neighboring preoptic regions

We have previously reported that intracerebroventricular injection of prostaglandin E₂ (PGE₂) induces hyperthermia possibly through EP₁ receptors in the rat. In the present study, to determine the sites in the brain where PGE₂ induces hyperthermia through EP₁ receptors, we microinjected an EP₁ receptor agonist, 17-phenyl-ω-trinor PGE₂ (17-Ph- PGE₂, 100 ng) into different sites in the rat brain and observed the colonic temperature (T(co)) for 2 h in a 23 ± 1°C environment. Responsive sites where 17-Ph-PGE₂ (100 ng) produced a rise in the T(co) of more than 1.1°C within 60 min after injection were found in the medial preoptic area, the subchiasmatic portion of the median preoptic nucleus, the anterior wail of the third ventricle (A3V) and the ventral portion of the diagonal band of Broca. Among these sites, the A3V was the most responsive. In contrast, microinjection of neither butaprost (an EP₂ agonist, 100 ng) nor M and B28767 (an EP₃ agonist, 100 ng) into these four sites had any effect on the T(co). Intracerebroventricular pretreatment with SC-19220 (an EP₁ antagonist, 100 μg) inhibited the rise in the T(co) which was induced by microinjection of PGE₂ (50 ng) into the A3V. These results thus suggest that PGE₂ induces hyperthermia by stimulating EP₁ receptors in the A3V and the neighboring preoptic region.