Oxytocin may mediate the benefits of positive social interaction and emotions

During breastfeeding or suckling, maternal oxytocin levels are raised by so matosensory stimulation. Oxytocin may, however, also be released by nonnoxi ous stimuli such as touch? warm temperature etc. in plasma and in cerebrosp inal fluid. Consequently, oxytocin may be involved in physiological and beh avioral effects induced by social interaction in a more general context. In both male and female rats oxytocin exerts potent physiological antistress effects. If daily oxytocin injections are repeated over a 5-day period, blo od pressure is decreased by 10-20 mmHg, the withdrawal latency to heat stim uli is prolonged, cortisol levels are decreased and insulin and cholecystok inin levels are increased. These effects last from 1 to several weeks after the last injection. After repeated oxytocin treatment weight gain may be p romoted and the healing rate of wounds increased. Most behavioral and physi ological effects induced by oxytocin can be blocked by oxytocin antagonists . In contrast, the antistress effects can not, suggesting that unidentified oxytocin receptors may exist. The prolonged latency in the tail-flick test can be temporarily reversed by administration of naloxone, suggesting that endogenous opioid activity has been increased by the oxytocin injections. In contrast, the long-term lowering of blood pressure and of cortisol level s as well as the sedative effects of oxytocin have been found to be related to an increased activity of central alpha(2)-adrenoceptors. Positive socia l interactions have been related to health-promoting effects. Oxytocin rele ased in response to social stimuli may be part of a neuroendocrine substrat e which underlies the benefits of positive social experiences. Such process es may in addition explain the health-promoting effects of certain alternat ive therapies. Because of the special properties of oxytocin, including the fact that it can become conditioned to psychological state or imagery, oxy tocin may also mediate the benefits attributed to therapies such as hypnosi s or meditation. (C) 1998 Elsevier Science Ltd. All rights reserved.