From behavior to membranes: testosterone-induced changes in action potential duration in electric organs.

The electric organ of mormyrid fishes consists of action potential-generating cells called electrocytes, which together produce a pulse-like electric organ discharge (EOD). The appearance of an EOD depends, in part, on the characteristic features of a single electrocyte's action potentials. In some species, gonadal steroid hormones induce increases in EOD duration, which mimic natural sex differences. We now show that testosterone-induced changes in EOD duration are associated with a 2- to 3-fold increase in the duration of action potentials generated by single electrocytes. Together with other anatomical and biochemical data, the results emphasize the exquisite interrelationship between steroid hormone action and the cellular machinery determining the electrical properties of single cells that underlie sexually dimorphic and seasonal behaviors.