Stress-induced depression of basal motility: effects of antidepressant drugs

Behavioral and biochemical effects of repeated immobilization stress were determined in male Wistar rats. The influence of acute or repeated administration of antidepressant drugs on these effects of stress were also evaluated. It was found that repeated stress (immobilization 3 h/2 degrees C/4 days or various stressors/8 days) reduced basal locomotor activity of rats and prolonged immobility time in Porsolt's despair test. Antidepressant drugs (desmethylimipramine, imipramine, amitriptyline, clomipramine, mianserine), given acutely, restored basal locomotor activity of stressed rats to control level. Desmethylimipramine, imipramine and amitriptyline reduced immobility time in Porsolt's test similarly in control as in stressed rats. However clomipramine, mianserine and trazodone were effective in this test only in stressed rats. Imipramine given for 4 or 8 days (1 h before the stressor) normalized basal locomotor activity. Repeated (for 8 days) various stressors decelerated utilization of noradrenaline (NA) and dopamine (DA) in the brain. Imipramine given once a day for 8 days (1 h before the stressor) normalized brain utilization of catecholamines (CA). It was proposed that depression of basal motility and reduction of CA utilization in the brain induced by repeated stress may be counter acted by antidepressant drugs.