Hypoxia induces oxytocin release in the rat.

These studies were undertaken to investigate the impact of hypoxia on the release of oxytocin (OXT) at the median eminence (ME) in adult male rats, and the possible glucocorticoid involvement in modulating this release. Hypoxia was achieved in a hypobaric chamber. The results were as follows: (a) Acute hypoxic stress induced a release of OXT in ME proportional to its intensity and duration. (b) Chronic hypoxia (5-25 days) had no statistically significant influence on the ME level of OXT. (c) After bilateral adrenalectomy (ADX), the levels of OXT in ME were decreased, and there were no further significant changes in these levels when the rats were exposed to hypoxia. (d) The decrease of OXT in ME of ADX rats was partly reversed by replacement with dexamethasone (DEX, i.p. 500 &mgr;g/rat). These results suggest that acute hypoxia produces an intensity- and duration-dependent release of OXT and that such release may be modulated in part by hypoxia-activated high circulating glucocorticoids and their negative feedback on the release of corticotropin releasing hormone (CRH).