Prostaglandin E2 has antinociceptive effect through EP1 receptor in the ventromedial hypothalamus in rats

Abstract

The effects of microinjection of prostaglandin E(2) (PGE(2)) (50 fg-50 ng/0.2 microl) into the ventromedial hypothalamus (VMH) on nociception were studied using a hot-plate test in rats. Microinjection of PGE(2) (5-500 pg and 50 ng/0.2 microl) 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 PGE(2) at 5 pg. Subsequently, to determine whether the PGE(2) receptor subtype EP(1) is involved in the PGE(2)-induced antinociceptive effect in the VMH, we observed the changes in nociception after intraVMH microinjection of SC19220, an EP(1) receptor antagonist, and 17-phenyl-omega-trinor PGE(2), an EP(1) receptor agonist. Simultaneous injection of SC19220 (150 ng) with PGE(2) (500 pg) into the VMH blocked the PGE(2)-induced prolongation of the paw-withdrawal latency. Moreover, an intraVMH microinjection of 17-phenyl-omega-trinor PGE(2) (500 pg) prolonged it. These results indicate that PGE(2) in the VMH has antinociceptive effect through its actions on EP(1) receptors in rats.

The prostaglandin E2 EP1 receptor mediates pain perception and regulates blood pressure

“…By contrast, the EP1-deficient mice were produced on an inbred DBA/1lacJ background. Recent studies in which PGE 2 and PGE analogues were microinjected into the rat ventromedial hypothalamus are also consistent with a role for EP1 receptors in the antinociceptive actions of PGE 2 (30). Alternatively, it is possible that signals from both the EP1 and IP receptors are involved in the acetic acid response and that the absence of either receptor alone is sufficient to attenuate the response.…”

International Union of Basic and Clinical Pharmacology. LXXXIII: Classification of Prostanoid Receptors, Updating 15 Years of Progress

“…This time-dependent late phase response was not observed for EP 2 and EP 4 agonists (Bä r et al, 2004). Set against these findings with respect to EP 1 receptors in the spinal dorsal horn mediating hyperalgesia, microinjection of PGE 2 into the ventromedial hypothalamus produced an EP 1 receptor-mediated antinociceptive effect (Hosoi et al, 1999). Electrophysiological evidence has been provided for EP 1 -mediated hypoalgesia in response to noxious pinching of facial skin after lateral cerebroventricular administration of a receptor selective agonist and antagonists .…”

Analgesic Effects of Thiamine in Male Long Evans Rats

“…The abdominal injection of acetic acid in rats has been attributed to the release of arachidonic acid, which results the synthesis of prostaglandin by the cycloxygenase enzyme 44 . On release of prostaglandin the special nerve endings act via prostaglandin E 2 receptor and transmit the signal to the brain and results in visceral writhing response 45 . Moreover, the response is also thought to be mediated by peritoneal mast cells 43 as well as acid sensing ion channels 46 .…”

“…Writhing test 27,[40][41][42][43][44][45][46] : All the rats of this test were also acclimatized to the laboratory environment as well as to the plexiglass observation chamber (30×30×30 cm 3 ) for 7 days prior to the final experimental day. Then on the day of experiment (Day 7)), 1 hour after the last dose of i.p.…”