Analgesic potency of sodium salicylate, indomethacin, and chlordiazepoxide as measured by the spatial preference technique in the rat

Abstract

The analgesic potency of various doses of sodium salicylate (150, 200, 250, 300, 350 mg/kg), indomethacin (1.5, 2.0, 2.5, 3.0, 3.5, 5.0 mg/kg) and chlordiazepoxide (2.5, 5.0, 10.0, 20.0 mg/kg) were measured using the spatial preference technique. All three agents were active in a wide range of doses indicating that this technique is sensitive to the weak analgesics. The chlordiazepoxide data were interpreted to suggest that this tranquilizing agent may be able to impair the appreciation of the emotional (i.e., aversive) qualities of electric shock, thus reducing the animal's motivation to escape the noxious stimulus. A procedure for computing ED₅₀ estimates was also presented along with a summary of the ED₅₀ values for several standard narcotic and narcotic antagonist analgesics. Since this procedure is a reliable and sensitive index of drug-induced analgesia, it should be useful as a screening procedure in evaluating the analgesic potency of a wide variety of chemical agents.