The effects of salinity stress on the electrophysiological properties ofMya arenaria neurons

Abstract

The euryhaline, osmoconforming bivalveMya arenaria is frequently subjected to large fluctuations in environmental salinity which are reflected by changes in the ionic and osmotic composition of the blood. These salinity-induced changes in the extraneuronal medium produce alterations in the electrical properties of neurons of the isolatedMya visceral ganglion. Following acute exposure ofMya neurons to reduced salinity, the resting membrane potential transiently hyperpolarizes and then abruptly depolarizes. These changes are accompanied by alterations in the apparent input resistance and, in addition, by a decrease in excitability, as evidenced by a loss or reduction of the TTX-sensitive action potentials. While a reduction in osmotic pressure produces some of these changes, others are produced by the reduced ionic concentration that also accompanies salinity stress. After several hours, the resting membrane potential repolarizes to near initial levels and the action potentials recover. Furthermore, neurons from animals acclimated to low salinity exhibit electrophysiological properties similar to those from neurons from animals kept in full-strength (100%) seawater, indicating that the neurons have adapted to the reduced environmental salinity.