NEONATAL HANDLING REDUCES EMOTIONAL REACTIVITY AND SUSCEPTIBILITY TO LEARNED HELPLESSNESS - INVOLVEMENT OF CATECHOLAMINERGIC SYSTEMS

Environmental circumstances during the neonatal period are critical fo r the establishment of adult responses to stressful environmental situ ations. As these responses are underpinned by adaptations in the funct ioning of brain neurotransmitter systems, the present study was design ed to assess the mediation of noradrenergic and dopaminergic systems i n the long-lasting effects of neonatal handling on both emotionality a nd learned helplessness behaviour. Animals received either prazosin, p ropranolol, haloperidol or saline before infantile handling. When the animals were 2 months old, they were subjected first to an open field test and then to the learned helplessness paradigm. Non-treated handle d animals exhibited lower emotional reactivity and reduced susceptibil ity to helplessness compared to non-treated non-handled rats. The resu lts suggest that noradrenergic, but not D2-dopamine receptor systems m ediate the influence of neonatal handling on the acquisition of learne d helplessness in the adult. Only beta-adrenoceptors appear to play a role in emotional responsiveness.