Intrathecal administration of sodium nitroprusside, a nitric oxide donor, increases blood pressure in anesthetized rats.

ABSTRACT

The present study was performed to investigate the role of spinal nitric oxide (NO) in the central regulation of blood pressure (BP). Experiments were carried out in anesthetized artificially ventilated male Wistar rats. Intrathecal (i.t.) administration of drugs was made at the thoracic spinal level. I.t. injection of a NO donor, sodium nitroprusside (SNP; 1, 5, and 15 nmol) increased BP dose-dependently. Intrathecal pretreatment of methylene blue (200 nmol) significantly attenuated the pressor response evoked by SNP (15 nmol, i.t.). I.t. administration of nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (100 and 1000 nmol), caused decreases in BP. These results suggest that NO plays a tonic excitatory role in the central regulation of BP in the rat spinal cord.