COMPARISON OF THE EFFECT OF REVERSIBLE AND IRREVERSIBLE MAO INHIBITORS ON RENAL NERVE ACTIVITY IN THE ANESTHETIZED RAT

Cardiovascular effects of the irreversible MAO-A inhibitor clorgyline and reversible MAO-inhibitors, moclobemide and brofaromine, were compa red in the anesthetized rat. Electrical activity of the sympathetic re nal nerve was monitored as an index of central sympathetic output. A l ong lasting decrease in the recorded parameters: blood pressure (BP), renal nerve activity (RNA) and heart rate (HR) was produced by acute a dministration of clorgyline (2mg/Kg, IP). Acute treatment with moclobe mide (10mg/Kg, IP) or brofaromine (10mg/Kg, IP) caused only a transien t decrease in RNA. Pretreatment with the alpha(2) antagonist yohimbine , decreased significantly the inhibitory effect of clorgyline on all t hree parameters. The selective alpha(2) antagonist CH-38083 blocked th e sympathoinhibitory effect of brofaromine. These results indicate an alpha(2) adrenoceptor involvement in the central sympathoinhibitory ef fect of MAO inhibitors, which may be manifested as a hypotensive effec t, including orthostatic hypotension, in patients treated with irrever sible selective MAO inhibitors.