COOLING EFFECTS ON NITRIC-OXIDE PRODUCTION BY RABBIT EAR AND FEMORAL ARTERIES DURING CHOLINERGIC STIMULATION

1 Ear (cutaneous) and femoral (deep) arteries from rabbit were perfuse d at 37 degrees C and 24 degrees C (cooling) and the production of nit rite, as an index of nitric oxide production, was measured under basal conditions and cholinergic stimulation. 2 In both types of arteries u nder control conditions, the basal production of nitrite was similar a t 24 degrees C and 37 degrees C. Compared with the control conditions, the basal production of nitrite was significantly lower in ear and fe moral arteries without endothelium or treated with N-G-nitro-L-arginin e methyl ester (L-NAME, 10(-4) M) but it was similar in those treated with atropine (10(-6) M). 3 At 37 degrees C, methacholine (10(-7)-10(- 5) M) increased the production of nitrite in ear and femoral arteries; this increase persisted during 30-60 min and was practically abolishe d by L-NAME (10(-4) M), atropine (10(-6) M), or removal of the endothe lium. In ear arteries the total nitrite production to activation with methacholine was higher at 24 degrees C than at 37 degrees C due to th is production persisted increased for a longer period (>150 min), wher eas in femoral arteries it was lower at 24 degrees C than at 37 degree s C. 4 It is suggested that: (a) the endothelium of rabbit ear and fem oral arteries produce nitric oxide under basal conditions, which is in creased by cholinergic stimulation, and (b) cooling potentiates endoth elial nitric oxide production to cholinergic stimulation in cutaneous arteries, whereas it inhibits this production in deep arteries.