Therapeutic and hypothermic properties of diazepam altered by a diazepam-chlorpromazine association

Rats were injected (IP) with diazepam (2.5 mg/kg) and chlorpromazine (10.0 mg/kg) with a 30-min interval between the two injections. After 10-12 repeated drug pairings of this type, the thermic, muscle relaxant, and anxiolytic responses of the animals to diazepam alone were tested. These tests revealed: 1) an enhanced hypothermia (rectal temperature), 2) an attenuated muscle relaxant effect (inclined plane test), and 3) a potentiated anxiolytic effect (plus-maze test). Although various interdrug associations have previously been demonstrated using other measures of conditioning, this is the first instance in which changes in the therapeutic effects of a drug (in this case, muscle relaxation and anxiety reduction) have been obtained with this procedure.