Analgesic potencies of non-narcotic, narcotic and anesthetic drugs as determined by the bradykinin-induced biting-like responses in rats.

Aversive (nociceptive) biting-like responses induced by micro-application of bradykinin solution onto rat tooth pulp were dose-dependently suppressed by non-narcotic drugs such as baclofen and lidocaine as well as carbamazepine and phenytoin, which are employed for clinical treatment of trigeminal neuralgia. The potency order of these drugs on a molar basis is baclofen (4.20) greater than carbamazepine (1.00) greater than lidocaine (0.94) greater than phenytoin (0.19). Such responses were also inhibited by morphine, pentazocine and cyclazocine (potency ratio of the three general analgesics, 1.00:0.46:8.11), indomethacin (a non-narcotic and anti-inflammatory analgesic) and alpha-chloralose (an anesthetic). The latter drug produced an analgesic effect at doses much lower than those used for anesthesia. These findings suggest that our method is feasible for evaluating the activities of general and particular analgesic drugs in the trigeminal regions.