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  • Title: Cholecystokinin and gastric distension activate oxytocinergic cells in rat hypothalamus.
    Author: Renaud LP, Tang M, McCann MJ, Stricker EM, Verbalis JG.
    Journal: Am J Physiol; 1987 Oct; 253(4 Pt 2):R661-5. PubMed ID: 3661761.
    Abstract:
    Systemic administration of cholecystokinin octapeptide (CCK-8) prompts an abrupt increase in circulating levels of oxytocin (OXY) but not vasopressin (VP) in rats. The present study determined whether CCK-8 selectively stimulated OXY-secreting neurons in the hypothalamic supraoptic nucleus of pentobarbital-anesthetized male rats. Antidromically identified neurosecretory neurons were categorized into putative OXY- and VP-secreting cells on the basis of their firing patterns and response to peripheral baroreceptor activation. Of 36 OXY-secreting cells studied, 30 demonstrated a 50-200% increase in firing frequency within 2 min of administering CCK-8 by intravenous or intraperitoneal injection, whereas none of the eight VP-secreting neurons studied was activated. In related experiments, 4-10 ml of air were used to inflate an intragastric balloon in rats; 20 of 22 OXY-secreting neurons displayed an abrupt and readily reversible increase in firing frequency, whereas only 2 of 17 VP-secreting cells were activated. Gastric distension similarly elevated plasma OXY levels in unanesthetized rats with indwelling gastric cannulas. Together with previous findings that the effects of CCK-8 on OXY release were attenuated by gastric vagotomy, these observations clearly demonstrate the existence of a sensitive neural link between the stomach and the neurohypophysis in the rat.
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