The circulating neurohormone oxytocin (OT)
Une video de Jean Marc Israel, Directeur de Recherche à Bordeaux Neurocampus (23 Mai 2016)
In mammals, the circulating neurohormone oxytocin (OT) has a role during parturition and lactation. OT triggers the successive contractions of the uterine myometrium causing expulsion of foetus then placenta. In addition, OT also induces the contraction of the myoepithelial cells wrapping the alveoli in the mammary gland, causing milk let-down. OT is mainly produced by hypothalamic magnocellular OT neurones and released from their axon terminals located in the neurohypophysis, wherefrom OT enters the blood stream. The electrical activity of OT neurones determines the release of the neurohormone. In basal condition, OT neurons fire action potentials (APs) at a low frequency (0.1 to 10 Hz), leading to a low release of OT. In order to increase OT secretion (parturition & lactation), OT neurones display brief (2-8 s) periodic (every 2-10 minutes) high frequency discharges (HFD, 20-60 Hz) in burst of APs. This is illustrated in the first part of the video.
Then we provide further evidence that bursting activity in OT neurones is not linked to some intrinsic cellular property (Jourdain et al, J Neurosci, 1998) but rather reflects the rhythmic drive by an intrahypothalamic autonomous burst generator (Israel et al, Nat Commun, 2014 ; Israel et al, Front Neurosci, 2016). This is illustrated in the last part of the video.
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