Modulation of Baroreflex Activity by Exogenous and Endogenous NO in SD Rats / 航天医学与医学工程

ABSTRACT

Objective To assess the modulation of baroreflex activity by exogenous and endogenous nitric oxide (NO) in SD rats. Method The normal baroreflex sensitivity of SD rat was evaluated by intravenous (I.v.) administration of Phenylephrine (PE, 30 μg·kg-1) to elevate blood pressure. Exogenous and endogenous nitric oxide (NO) were respectively produced by I.v. Infusion of sodium nitroprusside (SNP, 10.2 μg·kg-1) and L-arginine (L-Arg, 25 mg·kg-1). And NG-nitro-L-arginine methylester (L-NAME, 10 mg·kg-1) was infused to inhibit the generation of NO. Meanwhile, baroreflex sensitivity fluctuations caused by PE were estimated. Result Compared with the normal state, L-Arg significantly reduced the baroreflex sensitivity (Gmax) and the slope coefficient τ of the blood pressure-heart rate curve [Gmax=-1.469±0.120 beats/(min·mmHg) vs. -0.664±0.080 beats/(min·mmHg), P<0.01; τ=0.0860.005 vs. 0.0490.007, P<0.05]. SNP also led to attenuation of Gmax and τ [Gmax=-1.277±0.392 beats/(min·mmHg) vs. -0.943±0.297 beats/(min·mmHg); τ=0.074豹0.027 vs. 0.071±0.023] but the changes were not significant. In contrast to L-Arg and SNP, L-NAME induced raise of Gmax and τ [Gmax=-0.705±0.231 beats/(min·mmHg) vs. -1.065±0.200 beats/(min·mmHg); τ=0.0450.011 vs. 0.0590.026], however, they were statistically insignificant. Conclusion The results demonstrated that NO imposes effect on baroreflex activity, and the behaviors of exogenous and endogenous NO are different. Endogenous NO may be involved in the regulation of autonomic nervous system via central nervous system or carotid sinus, and inhibits the baroreflex sensitivity.