Effect of beta-adrenergic and serotoninergic agents on the stress-induced behaviour of "learned helplessness" in rats

The phenomenon of "learned helplessness" is characterized by elements of motor, cognitive and emotional deficit, and it is particularly suitable to be used as a "model" of behavioural depression. There is no doubt about the central role of the cerebral noradrenaline and serotonin in the stress-induced behavioural deficit. The effects of two known beta-adrenoceptor agonists--salbutamol and trimetoquinol--and the beta-adrenergic blockers propranolol and compound 3B, with beta-blocking activity equipotent to that of propranolol, were investigated under conditions of "prophylactic" and "therapeutic" administration in rats subjected to stress by modelling of the behaviour of learned helplessness. Among the serotoninergic agents, the effects of 5-hydroxytryptophane and of the inhibitor of serotonin synthesis, parachlorophenylalanine, were studied. The experimental results show a favourable effect on the behavioural deficit, caused by the blocking of the adrenergic transmitter system and by increasing the activity of the serotoninergic system.