Artigo
Rostral ventrolateral medulla - A source of sympathetic activation in rats subjected to long-term treatment with L-NAME
Fecha
1999-10-01Registro en:
Hypertension. Philadelphia: Lippincott Williams & Wilkins, v. 34, n. 4, p. 744-747, 1999.
0194-911X
10.1161/01.HYP.34.4.744
WOS:000083486500007
Autor
Bergamaschi, Cassia Toledo [UNIFESP]
Campos, Ruy Ribeiro [UNIFESP]
Lopes, Oswaldo Ubriaco [UNIFESP]
Institución
Resumen
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<0.05), which was similar to the decrease produced by intravenous administration of hexamethonium. In normotensive rats, glycine microinjection reduced MAP from 106+/-4 to 60+/-3 mm Hg (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.