Elsevier

Brain Research

Volume 637, Issues 1–2, 21 February 1994, Pages 45-49
Brain Research

Release of angiostensin in the paraventricular nucleus in response to hyperosmotic stimulation in conscious rats: a microdialysis study

https://doi.org/10.1016/0006-8993(94)91215-7Get rights and content

Abstract

Angiotensin peptides are thought to act as neurotransmitter or neuromodulators in central osmoregulation. We tested the hypothesis that angiotensin peptides are released in the paraventricular nucleus (PVN) of the hypothalamus upon local osmotic stimulation. Brain microdialysis and radioimmunoassay (RIA) techniques were used to measure the release of immunoreactive angiotensin II (irANG II) in the PVN following direct stimulation of this area with hyperosmotic solutions. In conscious rats, perfusion of the PVN with 0.3 M and 0.6 M NaCl in artificial cerebrospinal fluid (aCSF) elicited concentration-dependent increases in irANG II release to 5.52 + 0.53, (P < 0.01, n = 8)and9.01 ± 1.03pg/100μl, (P < 0.001, n = 7), respectively, from basal values of 3.04 ± 0.46pg/100 μl. Local perfusion of the PVN with 1.2 M glucose in aCSF also resulted in an increased release of irANG II from 3.07 ± 0.87 to 6.24 ± 0.45pg/100μl (P < 0.05, n = 5). Fractionization of angiotensin peptides by HPLC followed by RIA revealed that ANG II (1–8) and ANG III (2–8) were released in similar amounts in the perfusate collected during 0.6 M NaCl stimulation (4.79 ± 0.69and3.45 ± 0.76pg/100 μl, respectively). Our results show that both, ANG II and ANG III are released in the PVN in response to local hyperosmotic stimulation. They support the concept that angiotensin peptides in the PVN are involved as neurotransmitters in central osmotic control.

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