The Difference in the Site of Actions of Tricyclic Antidepressants and Methamphetamine on the Duration of the Immobility in the Behavioral Despair Test

A single administration of tricyclic antidepressants reduced the duration of the immobility in the behavioral despair test. The escape-directed behavior of tricyclic antidepressant-treated rats was observed in a cylinder partially filled with water. In contrast, although methamphetamine also reduced the duration of the immobility, an increase in the general motor activity was shown in methamphetamine-treated rats. Tricyclic antidepressants injected into the medial amygdaloid nucleus, not into the nucleus accumbens, suppressed the duration of the immobility. Methamphetamine completely suppressed the duration of the immobility not only when injected into the medial amygdaloid nucleus, but also when injected into the nucleus accumbens. The present results suggest that in the rat behavioral despair test, the medial amygdaloid nucleus may play an important role in the selective reductive effect on the duration of the immobility.