The role of phospholipase C in arginine vasopressin secretion by rat hypothalami in vitro

G protein-coupled receptors in the hypothalamic paraventricular and supraoptic nuclei--serpentine gateways to neuroendocrine homeostasis

G protein-coupled receptors (GPCRs) are the largest family of transmembrane receptors in the mammalian genome. They are activated by a multitude of different ligands that elicit rapid intracellular responses to regulate cell function. Unsurprisingly, a large proportion of therapeutic agents target these receptors. The paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus are important mediators in homeostatic control. Many modulators of PVN/SON activity, including neurotransmitters and hormones act via GPCRs--in fact over 100 non-chemosensory GPCRs have been detected in either the PVN or SON. This review provides a comprehensive summary of the expression of GPCRs within the PVN/SON, including data from recent transcriptomic studies that potentially expand the repertoire of GPCRs that may have functional roles in these hypothalamic nuclei. We also present some aspects of the regulation and known roles of GPCRs in PVN/SON, which are likely complemented by the activity of 'orphan' GPCRs.

Gene regulation system of vasopressin and corticotropin-releasing hormone

The neurohypophyseal hormones, arginine vasopressin and corticotropin-releasing hormone (CRH), play a crucial role in the physiological and behavioral response to various kinds of stresses. Both neuropeptides activate the hypophysial-pituitary-adrenal (HPA) axis, which is a central mediator of the stress response in the body. Conversely, they receive the negative regulation by glucocorticoid, which is an end product of the HPA axis. Vasopressin and CRH are closely linked to immune response; they also interact with pro-inflammatory cytokines. Moreover, as for vasopressin, it has another important role, which is the regulation of water balance through its potent antidiuretic effect. Hence, it is conceivable that vasopressin and CRH mediate the homeostatic responses for survival and protect organisms from the external world.

A tight and elaborate regulation system of the vasopressin and CRH gene is required for the rapid and flexible response to the alteration of the surrounding environments. Several important regulatory elements have been identified in the proximal promoter region in the vasopressin and CRH gene. Many transcription factors and intracellular signaling cascades are involved in the complicated gene regulation system. This review focuses on the current status of the basic research of vasopressin and CRH. In addition to the numerous known facts about their divergent physiological roles, the recent topics of promoter analyses will be discussed.

Specific up-regulation of CRH or AVP secretion by acetylcholine or lipopolysaccharide in inflammatory susceptible Lewis rat fetal hypothalamic cells

Lewis (LEW/N) rats, compared to Fischer (F344/N) rats, are susceptible to inflammatory/autoimmune diseases, in part, as a result of their blunted hypothalamic-pituitary-adrenal (HPA) axis responses. We examined regulation of LEW/N and F344/N fetal hypothalamic cell secretion of corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP), two major HPA axis mediators, by inflammatory and neurotransmitter stimuli. Interleukin-1beta (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and protein kinase A (PKA) and protein kinase C (PKC) activators did not affect LEW/N basal secretion. Compared to F344/N, LEW/N cells were hyporesponsive to lipopolysaccharide (LPS), serotonin (5-HT), and acetylcholine chloride (ACh). However, LPS-induced AVP release and ACh-evoked CRH secretion in LEW/N were comparable with those of F344/N. Our findings suggest that the blunted LEW/N neuropeptide response was more likely related to components of second messenger systems, rather than to any one specific stimulus.