Abstract
PROVIDING SUFFICIENT MILK to nursing young is necessary for infant survival and depends on periodic bolus secretion of oxytocin (OT) from the neurohypophysis during suckling. This pulsatile release maximizes myoepithelial cell contractions in the mammary gland by avoiding OT receptor desensitization (37, 44). Underlying the periodicity is the brief (4 – 6 s), synchronous, and explosive bursting of OT neurons in the supraoptic (SON) and paraventricular nuclei (PVN), the axons of which terminate at the neurohypophyseal neurohemal contact zone. These bursts (and the resultant OT release) appear with remarkably long intervals (5–20 min) despite the continual nipple stimulation provided by pups (30, 32, 38, 39), and are seldom observed during other periods of enhanced OT release. The bursting pattern maximizes frequency-dependent facilitation of OT release at neurohypophyseal terminals, and minimizes release fatigue (3–5). Understanding this periodicity remains one of the greatest challenges for OT neurobiologists. This system undergoes astonishing physiological plastic changes during pregnancy and lactation that should provide instructive clues to the process. It is now appreciated that OT
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More From: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology
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