OXYTOCIN LINKED ANTISTRESS EFFECTS - THE RELAXATION AND GROWTH-RESPONSE

Stress or noxious stimuli of various kind may induce the fight-flight response. In this situation a number of physiological and behavioural adaptations leading to defense of the organism occur. At a central lev el increased activity in the noradrenergic locus coeruleus (LC) and an enhanced secretion of corticotrophin-releasing factor (CRF) and vasop ressin produced in the paraventricular nucleus (PVN) integrate stress response. Here the existence of an opposite psycho-physiological patte rn associated with relaxation and growth and which is activated by cer tain types of non-noxious stimuli and integrated by oxytocin is propos ed. In support of this, administration of oxytocin to male and female rats gives rise to effects of antistress nature in particular after re peated administration. Thus a five day treatment period with oxytocin 1 mg/kg s.c. or 1 micro g/kg i.c.v gives rise to sedation, lowering of blood pressure, increased withdrawal latency in the tail flick test a nd also a decrease of corticosterone levels and a rise of certain vaga lly controlled hormones. Weight gain is also increased under certain c onditions. These effects persist several weeks after administration of oxytocin and cannot be reversed by oxytocin antagonists when establis hed, suggesting that secondary mechanisms have been activated. Naloxon e temporarily reverses the increased withdrawal of the tail flick test suggesting that opioid mechanisms have been activated to cause this p articular effect. In contrast the sedative and blood pressure lowering effect seems to be induced by an enhanced activity in central cc,rece ptors. Oxytocin levels increase in blood and CSF after various kinds o f non-noxious sensory stimulation such as touch, light pressure and wa rm temperature in both female and male rats. It is suggested that othe r types of non-nonxious stimuli as well may increase oxytocin release. If so, a release of oxytocin could be responsible for not only the an tistress effects occurring during lactation but also why relationships , social contact and networks may have health promoting effects in par ticular by preventing cardiovascular disease.