Simultaneous measurements of calcium mobilization and afferent nerve activity in electroreceptor organs of anesthetized Kryptopterus bicirrhis.

The transduction pathway of ampullary electroreceptor organs involves ionic currents. It has been shown that calcium, as well as sodium and potassium play important parts in this process. In this study we examine the stimulus-evoked changes in the Fura-2 ratio in electroreceptor cells. Furthermore, we recorded stimulus-evoked Fura-2 ratio changes while Na+ and K+ channels were blocked by amiloride and TEA. Simultaneously, extracellular recordings of the afferent spike activity were made. The results show the presence of stimulus evoked fluctuations in the Fura-2 ratio. These fluctuations can be abolished by the application of Cd2+, TEA, and amiloride. The stimulus-evoked activity of the afferent nerve was decreased due to application of these drugs. We conclude that the transduction current is carried by Na+, K+, and probably Ca2+. This fits the existing model on transduction in electroreceptors.