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Vasopressin is a small neuropeptide initially identified as the physiologically essential antidiuretic hormone more than 50 years ago. Since then, it has increasingly become apparent that vasopressin is an important hormonal component of the response to stress. In fact, it appears that the antidiuretic effect is only one of several biologically significant actions of vasopressin exerted during the response to stress. This review highlights the main features of vasopressin as a stress hormone produced by relatively simple hypothalamic neurons that release their neurotransmitters into the blood stream and also send axonal projections to key parts of the brain that control the response to stressful environmental challenges. Special focus is on the role of vasopressin in (1) setting the efficacy of adrenal corticosteroid feedback inhibition; (2) the stress of pain; and (3) supporting the response to inflammation.

This article reviews the hypothalamic control of anterior pituitary hormone secretion. The anterior pituitary gland plays a pivotal role in the hormonal response to stress, as it is the source of adrenocorticotropin and prolactin. The involvement of the posterior and intermediate pituitary lobes in the stress response is also considered.

Publisher Summary This chapter presents methods for direct radioligand measurement of oxytocin receptors in anterior pituitary gland. The cellular actions of oxytocin are mediated by binding to cell surface receptors on target cells. In addition to its well-defined peripheral actions in the uterus and the mammary gland, oxytocin may also function as a hypothalamic releasing hormone for prolactin, a central nervous system neurotransmitter involved in reproductive functions, and a paracrine hormone in the gonads. At present, all methods for measuring oxytocin receptors are based on the binding of radioligands. The most widely used probe is tritium-labeled oxytocin. The classic receptor criteria of reversibility, saturability, and high affinity can be readily tested using established procedures. In the case of the adenohypophyseal oxytocin receptors, the association of the radioligand to membrane suspensions reaches a steady state by 60 min. Binding saturation studies show that the specific component of the binding is saturable. No appreciable effect on the binding of OTA or on the potency of oxytocin to displace OTA is observed, indicating that the effects of manipulating G proteins are minimal compared with the changes brought about by altering Mg 2+ .