INTRATHECAL NEUROMEDIN-C ENHANCES MECHANICAL NOCICEPTION - POSSIBLE INVOLVEMENT OF NMDA RECEPTORS

Intrathecal administration of neuromedin C (3, 10 nmol/rat) significan tly decreased the nociceptive threshold of rats in the paw-pressure te st. This effect was abolished by co-administration of [Leu(13)psi(CH2N H)-Leu(14)]bombesin (10 nmol/rat), a bombesin receptor antagonist. Co- administration of 2-amino-5-phosphonovaleric acid (APV) at a dose (10 nmol/rat) which did not affect the nociceptive threshold by itself sig nificantly inhibited the effect of neuromedin C. 6-Cyano-7-nitroquinox aline-2,3-dione (CNQX) (10 nmol/rat) did not significantly inhibit the neuromedin C-induced hyperalgesia. These results indicate that neurom edin C could modulate mechanical nociception through bombesin receptor s at the spinal level, where glutamate is involved through NMDA recept ors.