Rostral Ventrolateral Medulla

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Abstract
Abstract —The major aim of the present study was to evaluate the role of the rostral ventrolateral medulla (RVLM) in the maintenance of hypertension in rats subjected to long-term treatment with N G -nitro- l -arginine methyl ester (L-NAME) (70 mg/kg orally for 1 week). We inhibited or stimulated RVLM neurons with the use of drugs such as glycine, l -glutamate, or kynurenic acid in urethane-anesthetized rats (1.2 to 1.4 g/kg IV). Bilateral microinjection of glycine (50 nmol, 100 nL) into the RVLM of hypertensive rats produced a decrease in mean arterial blood pressure (MAP) from 158±4 to 71±4 mm Hg ( P P <0.05). Glutamate microinjection into the RVLM produced a significant increase in MAP in both hypertensive rats (from 157±3 to 201±6 mm Hg) and normotensive rats (from 105±5 to 148±9 mm Hg). No change in MAP was observed in response to kynurenic acid microinjection into the RVLM in either group. These results suggest that hypertension in response to long-term L-NAME treatment is dependent on an increase in central sympathetic drive, mediated by RVLM neurons. However, glutamatergic synapses within RVLM are probably not involved in this response.