A field potential analysis of the electromotor system in Gymnotus carapo

Abstract

To investigate the synchronization mechanisms operating in the electromotor system, electric organ discharge related field potentials of neural origin were recorded in intact fish. Components corresponding to the relay nucleus, the bulbar-spinal electromotor tract, the electromotoneurons and the peripheral nerves were identified. Delays between components were used to estimate the following intervals: (1) the conduction time along the cord (central conduction interval), (2) the interval between the local activation of the tract and the electromotoneuron firing within a restricted portion of the cord (coupling interval) and (3) the conduction time along the peripheral axons plus the time taken by synaptic activation of the electrocytes (peripheral interval). While central conduction interval increases with the distance from the pacemaker, the coupling interval diminishes. Peripheral interval also diminishes from rostral to caudal targets in the electric organ. It is concluded that the electrocyte synchronization, resulting from matching the three above-defined intervals, is achieved by a cascade of synergetic mechanisms.