The osmoresponsiveness of oxytocin and vasopressin neurones: Mechanisms, allostasis and evolution

Abstract

In the rat supraoptic nucleus, every oxytocin cell projects to the posterior pituitary, and is involved both in reflex milk ejection during lactation and in regulating uterine contractions during parturition. All are also osmosensitive, regulating natriuresis. All are also regulated by signals that control appetite, including the neural and hormonal signals that arise from the gut after food intake and from the sites of energy storage. All are also involved in sexual behaviour, anxiety‐related behaviours and social behaviours. The challenge is to understand how a single population of neurones can coherently regulate such a diverse set of functions and adapt to changing physiological states. Their multiple functions arise from complex intrinsic properties that confer sensitivity to a wide range of internal and environmental signals. Many of these properties have a distant evolutionary origin in multifunctional, multisensory neurones of Urbilateria, the hypothesised common ancestor of vertebrates, insects and worms. Their properties allow different patterns of oxytocin release into the circulation from their axon terminals in the posterior pituitary into other brain areas from axonal projections, as well as independent release from their dendrites.

Peripheral insulin administration enhances the electrical activity of oxytocin and vasopressin neurones in vivo

“…In addition to their classical roles in reproduction, stress and water balance, oxytocin and vasopressin have roles in energy homeostasis . Both central and peripheral oxytocin administration exert anorexigenic effects, increase energy expenditure and induce lipolysis .…”

Robo2 regulates synaptic oxytocin content by affecting actin state

“…To validate our detection method, we subjected the fish to hypertonic osmotic challenge (25% sea salt) ( Fig. 1B), which is known to induce the release of oxytocin and vasopressin and, consequently reduced neuropeptide content in the pituitary of both mammals and fish (Balment et al, 1980;Huang et al, 1996;Leng and Russell, 2018;Pierson et al, 1995). We detected several hundreds of synapses and OXT-stained puncta in the neurohypophysis of naïve 8 days post-fertilization (dpf) zebrafish larvae.…”

Vasopressin & Oxytocin in Control of the Cardiovascular System: An Updated Review

“…OTRs were also found in the macula densa of the kidneys where they produce natriuresis by the modulation of tubuloglomerular feed-back and solute transport [84]. In addition, in the rat SON, every OT cell is osmo-sensitive that projects to the posterior pituitary [88]. Nonetheless, OT natriuretic properties have not been confirmed in humans [89,90].…”

“…It is now well established that brain peptides have actions that are not restricted to synapses [13,88]. Vesicles of peptidergic neurons are larger than vesicles of neurons carrying conventional transmitters, and have densely packaged cargo that may be released all along the neuron.…”