alpha(2)-Adrenergic receptors in NTS facilitate baroreflex function in adult spontaneously hypertensive rats.
We examined the effect of alpha(2)-adrenoreceptor blockade in the nucleus of the solitary tract (NTS) on baroreflex responses elicited by electrical stimulation of the left aortic depressor nerve (ADN) in urethane-anesthetized spontaneously hypertensive rats (SHR, n = 11) and normotensive Wistar-Kyoto rats (WKY, n = 11). ADN stimulation produced a frequency-dependent decrease in mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA), and heart rate (HR). In SHR, unilateral microinjection of idazoxan into the NTS markedly reduced baroreflex control of MAP, RSNA, and HR and had a disproportionately greater influence on baroreflex control of MAP than of RSNA. In WKY, idazoxan microinjections did not significantly alter baroreflex function relative to control vehicle injections. These results suggest that baroreflex regulation of arterial pressure in SHR is highly dependent on NTS adrenergic mechanisms. The reflex regulation of sympathetic outflow to the kidney is less influenced by the altered alpha(2)-adrenoreceptor mechanisms in SHR.
Hayward
Linda F
LF
Cardiovascular Center and Department of Internal Medicine, University of Iowa and Research Service of the Department of Veterans Affairs Medical Center, Iowa City, Iowa 52242, USA. lindah@ufl.edu
Riley
Alecia P
AP
Felder
Robert B
RB
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000758:Anesthesia; D000818:Animals; D001011:Aorta / Q000294:innervation; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure; D004558:Electric Stimulation; D006339:Heart Rate; D006710:Homocysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006973:Hypertension / Q000503:physiopathology*; D019329:Idazoxan / Q000008:administration & dosage / Q000494:pharmacology; D007668:Kidney / Q000294:innervation; D008297:Male; D008845:Microinjections; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology*; D017552:Solitary Nucleus / Q000187:drug effects / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology; D014520:Urethane
D000317:Adrenergic alpha-Antagonists; D018341:Receptors, Adrenergic, alpha-2; D006710:Homocysteine; C007956:homocysteic acid; D014520:Urethane; D019329:Idazoxan