[Physiological and sensorial determinism of maternal behavior in mammals]

In mammals, the development of maternal behaviour is generally controlled by neuroendocrine factors followed by sensory factors. Whereas the dynamics of the steroid balance at parturition are of primary importance in non-human mammals, stimulation of the uterine tract during the expulsion of the foetus is the key-factor in ungulates. This induces a cascade of physiological events and particularly the activation of the oxytocinergic system. The increase in prolactin release appears to be important only in rodents. Activation of the opiate system induces inhibitory effects in rodents and facilitatory effects in ungulates and, in rodents, the medial preoptic area is the central key structure of hormonal action. In women, no correlation exists between hormonal levels and maternal attitudes either during pregnancy or in the post-partum period. Physiological factors enhance receptivity to stimuli coming from the neonate and this allows the female to display maternal behaviour beyond this critical period. Odours facilitate the organisation of both maternal and infantile behaviour and are involved in individual recognition for both. Olfaction may also participate in the regulation of mother-young interactions in humans.