Angiotensin II immunoreactivity in the neural afferents and efferents of the subfornical organ of the rat

doi:10.1016/0006-8993(84)90174-4

Brain Research

Volume 321, Issue 2, 12 November 1984, Pages 209-215

https://doi.org/10.1016/0006-8993(84)90174-4 Get rights and content

Abstract

Angiotensin II (AII) immunoreactive cells and fibers were identified in the subfornical organ (SFO) of the rat. Cells were distributed in an annulus around the periphery of the SFO and were most visible in the Brattleboro rat treated with colchicine. Fibers were observed in a plexus, located centrally within the ring of cells, and knife-cuts suggested that they arise from parent cell bodies lying outside of the SFO. Studies combining immunohistochemistry with retrograde transport identified the perifornical zone of the lateral hypothalamus, the rostral zona incerta, and the nucleus reuniens of the thalamus as the source of AII-stained inputs to the SFO, and the region of the median preoptic nucleus as a recipient of AII-immunoreactive SFO efferents. It is suggested that these biochemically defined connections of the SFO participate in the central neural control of fluid balance.

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Citation Excerpt :
It might to be expented that the GABA subtypes may play distincttly different actions in the modulation of 5-HT release. Since neural inputs to the SFO come from the organum vasculosum lamina terminalis (OVLT), MnPO, lateral hypothalamic area, and several brainstem regions [4,19–21,31,35], it is suggested that one of the projections from these sites is the GABAergic inhibitory pathway. Indeed, an electrophysiological study has suggested that the anteroventral third ventricle (AV3V) region including the OVLT and the MnPO sends GABAergic inhibitory inputs to SFO neurons [31].
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The subfornical organ (SFO), vascular organ of the lamina terminalis (OVLT), area postrema (AP), pineal gland, subcommissural organ, median eminence–neurohypophysis (ME–NH), pineal gland and choroid plexus comprise the circumventricular organs (CVOs) of the rat brain. Located at strategic points along the walls of the lateral, third and fourth ventricles, these highly vascularized structures lack a blood–brain barrier (excepting the subcommissural organ), due to the presence of fenestrated endothelial cells lining their capillary walls. Only the SFO, OVLT and AP contain neuronal cell bodies. They are designated sensory CVOs; the others are termed secretory CVOs. Lack of a blood–brain barrier in sensory CVOs permits circulating humoral agents to interact directly with neurons located within them. Not surprisingly, these brain regions are rich in receptors for many peptides, monoamines and other signaling molecules. The SFO and OVLT located, respectively, at the dorsal and ventral ends of the midline anterior wall of the third ventricle have important roles in osmoreception and autonomic function that are mediated by direct afferent and efferent neural connections with regions of the hypothalamus, midbrain and hindbrain influencing thirst, vasopressin secretion, and cardiovascular regulation. The AP in the hindbrain has neural connections mainly with neurons of the adjacent medulla oblongata and midbrain that affect the baroreceptor reflex function and vomiting. The neurovascular arrangements in ME–NH (in the third ventricle floor) are crucial for secretion of pituitary hormones. Secretory products of the subcommissural organ influence brain development; while the choroid plexus elaborates cerebrospinal fluid.

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Angiotensin II immunoreactivity in the neural afferents and efferents of the subfornical organ of the rat

Abstract

Brain Research

Neuroscience

Pharmacol. Biochem. Behav.

Brain Research

Brain Research

Brain Research

Brain Research

Brain Research

Brain Research

Exp. Neurol.

Brain Research

Pharmacol. Biochem. Behav.

Brain Res. Rev.

Brain Research

Physio. Behav.

Brain Research

Plasma angiotensin-II levels and water intake following β-adrenergic stimulation, hypovolemia, cellular dehydration and water deprivation

Pharmacol. Biochem. Behav.