CHLORPROMAZINE INCREASES SODIUM PERMEABILITY ACROSS THE ISOLATED TOAD SKIN

The effects of chlorpromazine (Cpz) on the potential difference (PD), short-circuit current (SCC), and total conductance (G(T)) on Pleurodema thaul skin and on the skin response to dopamine were analysed. Cpz applied to the serosal surface in concentrations ranging from 1.25 x 10(-5) to 1.25 x 10(-4) M significantly increased the PD, the SCC and the G(T). The effect of Cpz was abolished by BaCl2 but not by alpha or beta adrenergic receptor antagonists. Cpz decreased the skin response to noradrenaline and to angiotensin II. Dopamine (5 x 10(-7) M to 5 x 10(-6) M) also induced a significant increase in the PD, SCC and G(T). This response was antagonized by propranolol but not by dibenamine. Additive effects of dopamine and Cpz were also found. The amiloride test showed that Cpz decreased E(Na), the driving force of sodium and increased G(Na), which represents active sodium conductance. These results are consistent with the hypothesis that Cpz increases transport across the isolated toad skin by increasing mucosal and serosal permeability. The results also suggest that Cpz decreases membrane calmodulin availability.