The inhibitory effects of salmon calcitonin on intrathecally-injected N-methyl-D-aspartate-induced aversive behavior in mice.

The effects of salmon calcitonin (SCT) on intrathecally-injected N-methyl-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 of SCT significantly inhibited acetic acid-induced writhing. Intrathecal (i.t.) injection of NMDA (0.25-1.0 nmol/mouse) dose-dependently induced aversive behavior such as scratching and tail biting. SCT at the doses of 0.01 and 0.1 IU/mouse (i.c.v.) significantly inhibited the NMDA-induced aversive behavior. This inhibitory effects of SCT on NMDA (i.t.)-induced aversive behavior were neither potentiated nor antagonized by i.c.v. injection of MK-801 and NMDA, respectively. Further, MK-801 (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 receptor/ionophore complex in the brain is not directly involved in the antinociceptive effects of intracerebrally-injected SCT.