[Comparative study of discriminative stimulus properties of antidepressants]

Interoceptive stimulus properties of amitriptyline (54 mg/kg body weight), fluoxetine (10 mg/kg), and pyrrolo[1,2-a][1,4]diazepine derivative GMAL-24 (10 mg/kg) were studied in a standard operant model with liquid reinforcement of drug discrimination (DD) in male Wistar rats. A new experimental schedule that includes subchronic (7-day) administration of a training drug was used to perform DD learning. For the first time, it was found that amitriptyline has a discriminative interoceptive stimulus properties. Neither fluoxetine nor GMAL-24 did exhibit interoceptive properties. Imipramine (15 mg/kg, i.p.) fully substitutes for amitriptyline stimulus in substitution test. Fluoxetine (5 - 20 mg/kg, i.p.) failed to substitute with amitriptyline. Thus, amitriptyline/saline drug discrimination should be used for a comparative analysis of the central mechanisms of action of psychotropic substances, rather than for screening specific antidepressant activity.