I. Hernandez et al., EFFECT OF N-OMEGA-NITRO-1-ARGININE METHYL-ESTER ON CARDIAC HEMODYNAMIC-RESPONSES TO ADENOSINE INFUSION IN CONSCIOUS RATS, General pharmacology, 26(1), 1995, pp. 143-148
1. The aim of the present study was to evaluate the role of NO in the
cardiovascular effects of adenosine in conscious rats. 2. Cardiac inde
x was determinated by thermodilution. In a group of rats, three doses
of adenosine were infused (i.v.) al a rate of 150, 300 and 450 mu g/kg
/min in the absence and in the presence of L-NAME (10 mg/kg). In a sec
ond group of rats, the experimental protocol was the same as that of t
he first group, except an infusion of methoxamine (50 mu g/kg/min) was
given during the second adenosine administration, instead of L-NAME.
3. In the absence of L-NAME or methoxamine, adenosine induced a dose-d
ependent decrease in mean arterial pressure and an increase in vascula
r conductance although adenosine did not affect cardiac index. 4. L-NA
ME administration attenuated the decreasing effect on the mean arteria
l pressure in response to the two lower doses of adenosine. In the pre
sence of L-NAME, adenosine induced a significant increase in cardiac i
ndex from 18.7 +/- 1.5 to 29.1 +/- 1.9 and 26.2 +/- 1.4 ml/min/100 g.
Administration of L-NAME significantly attenuated the adenosine-induce
d increase in vascular conductance. 5. Methoxamine infusion induced an
enhanced response to adenosine infusion. In the presence of methoxami
ne, adenosine induced a significant greater decrease in mean arterial
pressure, and increase in cardiac index and vascular conductance. 6. T
hese results indicate that part of the cardiovascular effects of adeno
sine can be mediated by NO, since L-NAME administration partially bloc
ked the adenosine-induced vasodilatation.