Intrathecal (i.t.) injection of the sulfated octapeptide cholecystokinin (CCK-8) elicited a behavioral response consisting of scratching, biting and licking in mice. CCK-8-induced behavioral response was evoked significantly 5 - 10 min after i.t. injection and reached a maximum at 20 - 25 min. Dose-dependency of the induced response showed a bell-shaped pattern from 1 zmol to 25 pmol, and the maximum effect was observed at 10 amol and 10 pmol. The behavioral response elicited by CCK-8 (10 amol and 10 pmol) was dose-dependently inhibited by i.t. administration of CCK-B receptor antagonist, CI-988. The CCK-A receptor antagonist, SR-27897, had no effect on the response elicited by CCK-8. The tachykinin neurokinin-1 (NK₁) receptor antagonists, CP-99,994 and sendide, inhibited CCK-8 (10 pmol)-induced behavioral response in a dose-dependent manner. No significant reduction of CCK-8 (10 amol)-induced response was detected co-administration of NK₁ antagonists. These results suggest that the nociceptive behaviors induced by i.t. administration of CCK-8 are mediated through the spinal CCK-B receptors and NK₁ receptors.