Responsiveness of α2-adrenoceptor/I1-imidazoline receptor in the rostral ventrolateral medulla to cardiovascular regulation is enhanced in conscious spontaneously hypertensive rat. (3rd April 2019)

• Record Type: Journal Article
• Authors: Yamazato, Masanobu; Nakamoto, Minori; Sakima, Atsushi; Yamazato, Yoriko; Takishita, Shuichi; Ohya, Yusuke
• Is Part Of: Clinical and experimental hypertension. Volume 41:Number 3(2019)
• Page Start: 255
• Page End: 262
• Publication Date: 2019-04-03
• Subjects: Α2-adrenoceptor -- blood pressure -- I1-imidazoline receptor -- renal sympathetic nerve activity -- rostral ventrolateral medulla -- spontaneously hypertensive rat -- Wistar Kyoto rat; Hypertension -- Chemotherapy -- Periodicals; Hypotensive agents -- Periodicals; 616.132
• DOI: 10.1080/10641963.2018.1469641
• Languages: English
• ISSNs: 1064-1963

Abstract

ABSTRACT: Stimulation of α2-adrenoceptor/I1-imidazoline receptors in the rostral ventrolateral medulla decreases the blood pressure via sympathoinhibition. However, alteration of receptor responses in genetically hypertensive rats remains unclear. We examined cardiovascular responses of α2-adrenoceptor/I1-imidazoline receptor agonist and antagonists microinjected into the rostral ventrolateral medulla of conscious spontaneously hypertensive rats and normotensive Wistar Kyoto rats. Injection of 2-nmol clonidine—an α2-adrenoceptor/I1-imidazoline receptor agonist—unilaterally into the rostral ventrolateral medulla decreased the blood pressure, heart rate, and renal sympathetic nerve activity; the responses were significantly enhanced in spontaneously hypertensive rats than in Wistar Kyoto rats. Co-injection of 2-nmol 2-methoxyidazoxan (a selective α2-adrenoceptor antagonist) or 2-nmol efaroxan (an I1-receptor antagonist) with 2 nmol of clonidine attenuated the hypotensive and bradycardic effects of clonidine-only injection. Injection of 2-methoxyidazoxan alone increased the blood pressure and heart rate in spontaneously hypertensive rats, but not in Wistar Kyoto rats. These results suggest enhanced responsiveness of α2-adrenoceptor/I1-imidazoline receptors in the rostral ventrolateral medulla of spontaneously hypertensive rats.