The effects of microinjection of prostaglandin E2 (PGE2) (50 fg-50 ng/0.2 μl) into the ventromedial hypothalamus (VMH) on nociception were studied using a hot-plate test in rats. Microinjection of PGE2 (5-500 pg and 50 ng/0.2 μl) into the VMH significantly prolonged the paw-withdrawal latency on a hot plate 5 and 10 min after injection, respectively. Maximal prolongation was obtained 5 min after the injection of PGE2 at 5 pg. Subsequently, to determine whether the PGE2 receptor subtype EP1 is involved in the PGE2-induced antinociceptive effect in the VMH, we observed the changes in nociception after intraVMH microinjection of SC19220, an EP1 receptor antagonist, and 17-phenyl-ω-trinor PGE2, an EP1 receptor agonist. Simultaneous injection of SC19220 (150 ng) with PGE2 (500 pg) into the VMH blocked the PGE2-induced prolongation of the paw-withdrawal latency. Moreover, an intraVMH microinjection of 17-phenyl-ω-trinor PGE2 (500 pg) prolonged it. These results indicate that PGE2 in the VMH has antinociceptive effect through its actions on EP1 receptors in rats. Copyright (C) 1999 International Association for the Study of Pain. Published by Elsevier Science B.V.
All Science Journal Classification (ASJC) codes
- Clinical Neurology
- Anesthesiology and Pain Medicine