MAUTHNER CELL-INITIATED ABRUPT INCREASE OF THE ELECTRIC ORGAN DISCHARGE IN THE WEAKLY ELECTRIC FISH GYMNOTUS-CARAPO

Stimulation of the spinal cord of the electric fish Gymnotus carapo, e voked an abrupt increase in the discharge rate of the electric organ. At the maximum of this response, the rate increased an average of 26 /- 11.8%. The duration of the response was 4.9 +/- 2.12 s; its latency was 10.4 +/- 1.1 ms. Activation of the Mauthner axon played a decisiv e role in this phenomenon as indicated by the following: (1) recording s from the axon cap of the Mauthner cell demonstrated that the respons e was evoked if the Mauthner axon was antidromically activated and 2) a response that was similar to that produced by spinal cord stimulatio n, was elicited by intracellular stimulation of either Mauthner cell. Stimulation of the eighth nerve could also increase the discharge rate of the electric organ. The effect was greater if a Mauthner cell acti on potential was elicited. The findings described in the present repor t, indicate the existence of a functional connection between the Mauth ner cell and the electromotor system in Gymnotus carapo. This connecti on may function to enhance the electrolocative sampling of the environ ment during Mauthner-cell mediated behaviors. This is a novel function for the Mauthner cell.