The toxicity of exposure to the organochlorine, dieldrin, at a sympathetic junction and on the skin of the frog,Caudiverbera caudiverbera

Abstract

The effects of the organochlorine, dieldrin, were tested on a noradrenergic synapse of the frog, Caudiverbera caudiverbera. Nerve stimulation induced a transient increase in short circuit current (SCC) and in the potential difference (PD), which consisted of a rapid and then a slow component. Dieldrin in the concentration range 0.01–1.0 mM caused a concentration-dependent block of both components to 32% of their control values, which was partially reversed by washout. In some experiments, this blocking effect was preceded by an initial increase in the magnitude of the electrical parameters of the nonstimulated skin and also in the synaptic response to stimulation when the lowest dieldrin concentration (0.01 mM) was applied; higher concentrations (0.1–1.0 mM) led to progressive reduction of the responses. Results are interpreted as a perturbation of the lipid bilayer structure, which affects the functionality of lipid–protein complexes, leading, on one hand, to glandular Cl¡ channel inactivation and epithelial Na + channel blockade and, on the other hand, to transient glandular Cl¡ activation, opening of a putative Na+channel, and subsequent blockade.