THE INHIBITORY EFFECTS OF SALMON-CALCITONIN ON INTRATHECALLY-INJECTEDN-METHYL-D-ASPARTATE-INDUCED AVERSIVE BEHAVIOR IN MICE

The effects of salmon calcitonin (SCT) on intrathecally-injected N-met hyl-D-aspartate (NMDA)-induced aversive behavior were investigated to clarify the involvement of the NMDA receptor/ionophore complex on the analgesic effects of SCT. Intracerebroventricular (i.c.v.) injection o f SCT significantly inhibited acetic acid-induced writhing. Intratheca l (i.t.) injection of NMDA (0.25-1.0 nmol/mouse) dose-dependently indu ced aversive behavior such as scratching and tail biting. SCT at the d oses of 0.01 and 0.1 IU/mouse (i.c.v.) significantly inhibited the NMD A-induced aversive behavior. This inhibitory effects of SCT on NMDA (i .t.)-induced aversive behavior were neither potentiated nor antagonize d by i.c.v. injection of MK-801 and NMDA, respectively. Further, MK-80 1 (i.c.v.) and NMDA (i.c.v.) themselves did not affect the NMDA (i.t.) -induced aversive behavior. These results suggest that the NMDA recept or/ionophore complex in the brain is not directly involved in the anti nociceptive effects of intracerebrally-injected SCT.