BLOCKADE OF DESENSITIZATION OF NICOTINIC RECEPTORS OF THE CAT ADRENAL MEDULLA BY CONCANAVALIN A

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Abstract
1 The possibility of concanavalin A (Con A) blocking the development of desensitization of nicotinic receptors of the cat adrenal gland has been investigated. 2 During perfusion of the adrenal gland with Krebs-bicarbonate solution containing acetylcholine (ACh), the rate of catecholamine (CA) secretion was very high in the first 2 min; thereafter, as perfusion with ACh was continued the output fell, to reach about 20% of the initial value in 10 minutes. When the adrenal gland was pretreated with Con A, the subsequent desensitization of release during continued infusion of ACh was prevented. 3 When the adrenal gland was perfused with high K+ solution, there was always a large initial secretion of CA, and as perfusion with high K+ continued the output fell, to reach about 15% of the initial rate in 10 minutes. Con A did not affect the rate of CA secretion induced by high K+. 4 It is tentatively suggested that Con A blocks the desensitization of CA secretion evoked by ACh by interaction with the glycoprotein moiety of the nicotinic receptor of adrenal chromaffin cells.