Spinal EP receptors mediating prostaglandin E 2–induced mechanical hyperalgesia, thermal hyperalgesia, and touch-evoked allodynia in rats

Abstract

Intrathecal administration of prostaglandin E 2 (PGE 2) produces mechanical hyperalgesia, thermal hyperalgesia, and touch-evoked allodynia in rats. Experiments were conducted to examine the effects of intrathecal administration of relatively selective PGE 2 receptor (EP receptor) agonists to establish which spinal EP receptors mediate these behavioral effects of spinally administered PGE 2. Administration of either sulprostone (EP 3 receptor agonist) or PGE 1 alcohol (EP 4 receptor agonist) produced marked mechanical and thermal hyperalgesia and touch-evoked allodynia. Neither 17-phenyl trinor PGE 2 (EP 1 receptor agonist) nor butaprost (EP 2 receptor agonist) produced any significant changes in behavioral response thresholds to mechanical or thermal stimuli. However, 17-phenyl trinor PGE 2 (EP 1 receptor agonist) did produce marked touch-evoked allodynia. These data suggest that in rats activation of spinal EP 3 and EP 4 receptors by PGE 2 is important for development of both mechanical and thermal hyperalgesia as well as for touch-evoked allodynia. PGE 2-induced allodynia also appears to involve activation of spinal EP 1 receptors.