AN INHIBITOR OF NITRIC-OXIDE SYNTHASE, N-OMEGA-NITRO-L-ARGININE-METHYL ESTER, ATTENUATES HYPOTENSION BUT DOES NOT IMPROVE CARDIAC DEPRESSION IN ANAPHYLAXIS IN DOGS

We investigated whether a nitric oxide synthase (NOS) inhibitor improv es cardiovascular depression associated with anaphylaxis. After induct ion of anaphylactic circulatory depression, one group received an NOS inhibitor (Group I, n = 6) and the other received saline solution (Gro up II, n = 5). Mean arterial pressure and right atrial pressure were s ignificantly higher in Group I than in Group II. Hematocrit was signif icantly lower in Group I than in Group II. Cardiac output, stroke volu me, mean pulmonary arterial pressure, the maximum rate of increase in left ventricular pressure, and the time constant of the fall in isovol umic left ventricular pressure did not differ between the groups. In c onclusion, L-NAME attenuates hypotension, but does not improve cardiac depression in anaphylaxis in dogs. Our finding that NOS inhibitor did not improve cardiac function implies that the production of NO in ana phylaxis may have a protective effect with regard to cardiac performan ce.