Difference in pressor responses to NG-monomethyl-L-arginine between conscious and anesthetized rats

NG-Monomethyl-L-arginine (L-NMMA; 0.1-10 mg/kg, i.v.), a selective inhibitor of nitric oxide (NO) synthesis derived from L-arginine, elicited a greater increase in blood pressure in urethane/alpha-chloralose- and pentobarbital-anesthetized rats than in conscious Wistar rats. The pressor response to phenylephrine was almost equivalent in both conscious and anesthetized rats. These findings suggest that the experimental conditions (anesthetized or conscious) modify the spontaneously released NO's contribution to blood pressure regulation in vivo.