NOCICEPTIVE EFFECTS INDUCED BY INTRATHECAL ADMINISTRATION OF PROSTAGLANDIN-D2, E2, OR F2-ALPHA TO CONSCIOUS MICE

The effects of intrathecal administration of prostaglandins on pain responses in conscious mice were evaluated by using hot plate and acetic acid writhing tests. Prostaglandin D2 (0.5-3 ng/mouse) had a hyperalgesic action on the response to a hot plate during a 3-60 min period after injection. Prostaglandin E2 showed a hyperalgesic effect at doses of 1 pg to 10 ng/mouse, but the effect lasted shorter (3-30 min) than that of prostaglandin D2. Similar results were obtained by acetic acid writhing tests. The hyperalgesic effect of prostaglandin D2 was blocked by simultaneous injection of a substance P antagonist (≥100 ng) but not by AH6809, a prostanoid EP1-receptor antagonist. Conversely, prostaglandin E2-induced hyperalgesia was blocked by AH6809 (≥500 ng) but not by the substance P antagonist. Prostaglandin F2α had little effect on pain responses. These results demonstrate that both prostaglandin D2 and prostaglandin E2 exert hyperalgesia in the spinal cord, but in different ways. © 1990.