INHIBITORY EFFECT OF MANGANESE ON NOREPINEPHRINE RELEASE FROM THE SPLENIC NERVES OF CATS

¹ Department of Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, New York

Norepinephrine (NE) was released from perfused spleens either by nerve stimulation or injection of potassium in phenoxybenzamine-treated and normal cats. Krebs-bicarbonate solution was perfused at a rate of about 7 ml/min at 35°C. Perfusion of the phenoxybenzamine-treated spleens with 2.5 mM Mn⁺⁺ Krebs' solution reduced the NE outputs to low levels. Perfusion of the normal spleens, pre-exposed to H³-NE infusion, with 0.8, 2.5 or 5 mM Mn⁺⁺ Krebs' solution also significantly reduced the net increases in radioactivity, H³-NE and NE by nerve stimulation. Increasing the Ca⁺⁺ concentration to 10 mM did not significantly alter the inhibitory effect of Mn⁺⁺. Mn⁺⁺ also blocked the spontaneous release of radioactivity from spleen. It is concluded that Mn⁺⁺ acts as a potent inhibitor of NE release and blocks both the nerve-induced and spontaneous release of NE.

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