DOUBLE NORADRENALINE EFFECT ON NON-ELECTROLYTE PERMEABILITY EXPLAINED BY ALPHA-RECEPTORS AND BETA-RECEPTORS STIMULATION IN FROG-SKIN

1. Noradrenaline (4 × 10-5 M) exerts two separate effects on nonelectrolyte permeability across the frog skin: (a) a secretion towards the external medium and (b) a symmetrical permeability increase in both directions. 2. The secretion is inhibited by phentolamine (an α adrenergic blocker) and by Ca2+ deprivation. 3. The symmetrical increase of permeability is absent either in the presence of DCI (a β adrenergic blocker) or of ADH. 4. Therefore the secretory effect could be due to the interaction of noradrenaline with α adrenergic receptors and Ca2+-mediated. The symmetric effect may be due to the interaction of noradrenaline with β adrenergic receptors and mediated by increased cAMP levels. © 1979.