Bidirectional neuro-glial signaling modalities in the hypothalamus: Role in neurohumoral regulation

Abstract

Maintenance of bodily homeostasis requires concerted interactions between the neuroendocrine and the autonomic nervous systems, which generate adaptive neurohumoral outflows in response to a variety of sensory inputs. Moreover, an exacerbated neurohumoral activation is recognized to be a critical component in numerous disease conditions, including hypertension, heart failure, stress, and the metabolic syndrome. Thus, the study of neurohumoral regulation in the brain is of critical physiological and pathological relevance. Most of the work in the field over the last decades has been centered on elucidating neuronal mechanisms and pathways involved in neurohumoral control. More recently however, it has become increasingly clear that non-neuronal cell types, particularly astrocytes and microglial cells, actively participate in information processing in areas of the brain involved in neuroendocrine and autonomic control. Thus, in this work, we review recent advances in our understanding of neuro-glial interactions within the hypothalamic supraoptic and paraventricular nuclei, and their impact on neurohumoral integration in these nuclei. Major topics reviewed include anatomical and functional properties of the neuro-glial microenvironment, neuron-to-astrocyte signaling, gliotransmitters, and astrocytes regulation of signaling molecules in the extracellular space. We aimed in this review to highlight the importance of neuro-glial bidirectional interactions in information processing within major hypothalamic networks involved in neurohumoral integration.

Obesity induces neuroinflammation mediated by altered expression of the renin–angiotensin system in mouse forebrain nuclei

“…There is also evidence that astrocyte-neuron interactions play an important role in neurohumoral and autonomic control, as reviewed in detail by Stern and Filosa [51]. Astrocytes are capable of sensing and responding to hypertensive and obesigenic stimuli [13, 37, 38].…”

“…Astrocytes are capable of sensing and responding to hypertensive and obesigenic stimuli [13, 37, 38]. They become activated during obesity [13, 38] and can then impact neuronal signaling within forebrain autonomic control centers through a variety of mechanisms [51]. For example, astrocytes can contribute to GABA tone in neural circuits that regulate sympathetic outflow and blood pressure via their GABA transporter 3, which removes GABA from the synapse thereby disinhibiting certain neural circuits [52].…”

Multiple signalling modalities mediated by dendritic exocytosis of oxytocin and vasopressin

“…changes in sympathetic/parasympathetic outflows to different target organs) along with a 'humoral' response, represented by the release of different neurohormones, including vasopressin, angiotensin and endothelins among others [105][106][107]. These neurohumoral responses generated by the PVN are critically important for the maintenance of cardiovascular and fluid balance homeostasis.…”

Small-Volume Analysis of Cell–Cell Signaling Molecules in the Brain

“…Equally fascinating as this morphological complexity is the chemical complexity and myriad forms of intercellular communication in the nervous system (Agnati et al, 2010). Neurons and glia have regulated secretory pathways (Stern and Filosa, 2013) where bioactive peptides and low-molecular-weight transmitters coexist in a cell and can even be released together. Cotransmission, however, is plastic and sensitive to environmental stimuli and pathological conditions.…”

“…Lipid messengers such as endocannabinoids are involved in short-and long-term synaptic plasticity throughout the brain (Katona and Freund, 2012;Pineiro and Falasca, 2012). The gases, nitric oxide (NO) and carbon monoxide, have unique physicochemical properties that enable them to diffuse across cell membranes, thus affecting receptors and other targets located hundreds of microns from the release site (Stern and Filosa, 2013). Neuropeptides are the largest and most functionally and structurally diverse class of cell-tocell signaling molecules.…”