Role of nitric oxide in regulation of renal sympathetic nerve activity during hemorrhage in conscious rats

Abstract

The effect of inhibition of nitric oxide (NO) synthesis on the responses of blood pressure (BP), heart rate (HR), and renal sympathetic nerve activity (RSNA) during hemorrhaging was examined with the use of an NO synthase inhibitor, N G-nitro-l-arginine methyl ester (l-NAME), in conscious rats. In the 0.9% saline group, hemorrhage (10 ml/kg body wt) did not alter BP but significantly increased HR and RSNA by 88 ± 12 beats/min and 67 ± 12%, respectively. Intravenous infusion of l-NAME (50 μg ⋅ kg−1 ⋅ min−1) significantly attenuated these tachycardic and sympathoexcitatory responses to hemorrhage (14 ± 7 beats/min and 26 ± 12%, respectively). Pretreatment ofl-arginine (87 mg/kg) recovered the attenuation of HR and RSNA responses induced byl-NAME (92 ± 6 beats/min and 64 ± 10%, respectively).l-NAME by itself did not alter the baroreceptor reflex control of HR and RSNA. Hemorrhage increased the plasma vasopressin concentration, and its increment in thel-NAME-treated group was significantly higher than that in the 0.9% saline group. Pretreatment with the vascular arginine vasopressin V1-receptor antagonist OPC-21268 (5 mg/kg) recovered the attenuation of RSNA response induced byl-NAME (54 ± 7%). These results indicate that NO modulated HR and RSNA responses to hemorrhage but did not directly affect the baroreceptor reflex arch. It can be assumed that NO modulated the baroreflex function by altering the secretion of vasopressin induced by hemorrhage.

Roles of adrenomedullin 2 in regulating the cardiovascular and sympathetic nervous systems in conscious rats

“…RSNA was recorded from the left renal nerve branch as previously described (4). Briefly, the renal nerve was isolated near the aortic-renal arterial junction and placed on a Teflon-coated stainless steel bipolar electrode with the aid of an operation microscope.…”

Effects of a New Calcium Channel Blocker, Azelnidipine, on Systemic Hemodynamics and Renal Sympathetic Nerve Activity in Spontaneously Hypertensive Rats

“…In addition, we compared the effects of azelnidipine on RSNA with those of amlodipine and sodium nitroprusside. Finally, we examined the effects of azelnidipine and amlodipine on baroreflex functions by analyzing baroreflex function curves (16).…”

Thyroid disorders and nitric oxide in cardiovascular adaptation to hypovolemia

“…This effect of NO seems to be lower in hypothyroidism in which basal values of MAP were not reached. However, we cannot throw away the effects of NO on the integrated mechanisms which become activated in response to haemorrhage as well as the release of several neurohormonal vasoconstrictor factors (catecholamines, endothelins, vasopressin, renin-angiotensin system) (Fujisawa et al 1999, Moreno et al 2002.…”

“…Activation of several neurohormonal factors (nitric oxide (NO), catecholamines, endothelins, vasopressin, renin-angiotensin system) is involved in the restoration of vascular volume and blood pressure following bleeding (Fujisawa et al 1999, Paczwa & Ganten 1999. This adaptive response to the decrease in the total blood volume implies a peripheral vasoconstriction which induces a redistribution of blood flow to the vital organs within which highlights the heart (Schadt & Hasser 2004).…”