Milk-ejection reflex

OT receptors are localized ia the brain hypothalamus, limbic system, cortex, striatum, olfactory system, and brain stem. In the periphery, OT is best known for its stimulation of uterine smooth muscle and the milk ejection reflex. Thr , Om ]oxytocin(l—8),... 

Although the OT system may be regarded as a key regulator of labour, in OT-deficient mice, parturition remains unaffected. Moreover, OTR knockout mice do deliver in a normal fashion, but the offspring die during the very first days of life, due to starving, as the milk ejection reflex is absent in these animals. These experiments show that the OT system is not essential for labour or reproductive behaviour (at least in mice), but for the milk ejection reflex, which is fundamental for litter survival. 

Consider, for example, the milk-ejection reflex. This behavior may not normally be triggered by pheromones, but it can occur within seconds of the onset of suckling or exposure to stimuli, including odors, that have become associated with suckling (Wakerly, Clarke, Summerlee, 1994). Milk ejection in these circumstances would therefore seem to qualify as a released response. But because milk ejection is secondary to the hormonal effects of oxytocin released from the posterior pituitary, the response would seem to qualify as a primed effect. 

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