These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Alpha2-adrenoceptor-mediated restraint of norepinephrine synthesis, release, and turnover during immobilization in rats.
    Author: Tjurmina OA, Goldstein DS, Palkovits M, Kopin IJ.
    Journal: Brain Res; 1999 May 01; 826(2):243-52. PubMed ID: 10224302.
    Abstract:
    Stress-related release of norepinephrine (NE) in the brain and periphery probably underlies several neuroendocrine and neurocirculatory responses. NE might influence its own synthesis, release, and turnover, by negative feedback regulation via alpha2-adrenoceptors. We examined central and peripheral noradrenergic function by measuring concentrations of NE, dihydroxyphenylglycol (DHPG), and dihydroxyphenylacetic acid (DOPAC) in hypothalamic paraventricular nucleus (PVN) microdialysate and arterial plasma simultaneously during immobilization (IMMO) in conscious rats. The alpha2-adrenoceptor antagonist yohimbine (YOH) was injected i.p. or perfused locally into the PVN via the microdialysis probe. The i.p. YOH increased plasma NE, epinephrine (EPI), DHPG, dihydroxyphenylalanine, and DOPAC levels by 4.3, 7.3, 2.5, 0.6 and 1.8-fold and PVN microdialysate NE, DHPG, and DOPAC by 1. 2, 0.6 and 0.5-fold. The i.p. YOH also enhanced effects of IMMO on plasma and microdialysate NE, DHPG, and DOPAC. YOH delivered via the PVN microdialysis probe did not affect microdialysate or plasma levels of the analytes at baseline and only slightly augmented microdialysate NE responses to IMMO. The results indicate that alpha2-adrenoceptors tonically restrain NE synthesis, release, and turnover in sympathetic nerves and limit IMMO-induced peripheral noradrenergic activation. In the PVN, alpha2-adrenoceptors do not appear to contribute to these processes tonically and exert relatively little restraint on IMMO-induced local noradrenergic activation.
    [Abstract] [Full Text] [Related] [New Search]