American journal of hypertension
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The Bezold-Jarisch reflex function was evaluated in rats made hypertensive by the chronic oral intake of a nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, averaging 35 mg/kg/day), for 3, 6, and 12 days (n = 9/group) and in untreated control rats (CR, n = 9/group). L-NAME-treated rats showed a marked hypertension (MAP: 148 +/- 3, 182 +/- 4, and 179 +/- 4 mm Hg, respectively) compared with CR (110 +/- 2 mm Hg). The 6- and 12-day groups showed tachycardia (447 +/- 20 and 466 +/- 13 beats/min, respectively) when compared with CR (355 +/- 10 beats/min). ⋯ Using a Langendorff technique, we observed a significant increase in the responsiveness of the pacemaker to acetylcholine (1.25 to 80 microg/mL). These data suggest that the pharmacological inhibition of the nitric oxide synthase causes profound changes in the mechanisms of cardiovascular regulation as shown by a marked enhancement of the Bezold-Jarisch reflex in L-NAME-treated rats. The enhancement of this reflex seems to be in great part due to the hyperresponsiveness of the cardiac pacemaker to cholinergic stimulation.