REDUCED GABA INHIBITION OF SYMPATHETIC FUNCTION IN RENAL-WRAPPED HYPERTENSIVE RATS

Animals with bilateral cannulas in the paraventricular nucleus were ma de hypertensive by a one-kidney, figure eight renal wrap procedure or sham operated. Femoral artery and vein catheters were inserted for art erial pressure measurement and plasma catecholamine determination. Aft er recovery and 4 days after hypertension surgery, bicuculline methiod ide or muscimol was microinjected into the paraventricular nucleus. In some rats, nitroprusside was infused intravenously to reflexly stimul ate the sympathetic nervous system. In control rats, bicuculline incre ased blood pressure, heart rate, and plasma norepinephrine and epineph rine concentrations. In contrast, in hypertensive rats blood pressure did not change while the heart rate response was maintained. Plasma no repinephrine and epinephrine responses were reduced 75 and 68%, respec tively. Muscimol injections decreased arterial pressure in the hyperte nsive rats. Heart rate responses to nitroprusside were similar in the two groups of rats, while the plasma catecholamine responses were atte nuated in the hypertensive animals. These data suggest that GABA funct ion in the paraventricular nucleus is reduced in renal wrap hypertensi on.