Regional blood flow determinations in the rat during paraoxon-poisoning and treatment with atropine and obidoxime.

Perfusion rates of various organs were determined for 4 different rat populations subjected, respectively, to: (a) 15 min infusion of paraoxon (150 micrograms/kg i.v.); (b) 15 min infusion of paraoxon and the injection of 1.0 mg/kg atropine; (c) 15 min paraoxon infusion and the injection of 10.0 mg/kg obidoxime; and (d) none of these substances. Atropine and obidoxime were both injected 10 min after the beginning of the paraoxon infusion. The perfusion rates were determined by means of the microspheres technique, which allows the simultaneous measurement of different perfusion rates. The paraoxon-treated animals revealed a significantly lower perfusion rate of the kidney, skeletal muscle, skin and spleen in comparison to the unpoisoned control group. The flow rates in heart, stomach, small intestine, liver (arterial) and brain changed only slightly. The injection of atropine caused the perfusion rates of heart, kidney, intestine and spleen to be greater than under paraoxon alone, Obidoxime, furthermore, induced significant increases in the perfusion rates of all 9 organs studied. Indeed, for several organs, the flow rates under atropine and obidoxime were greater than those of the controls. It is suggested that the effects of paraoxon, atropine and obidoxime on the organ flow rates are due to different influences on peripheral and central muscarinic and nicotinic receptors and to changes in the depth of respiration.