A new method for recording activities of spinal motoneurons during fictive swimming in paralyzed teleost fish

ABSTRACT: A new method for monitoring spinal motoneuron activities during fictive swimming in teleost fish was developed. Enamel-insulated copper wire electrodes were implanted in the trunk muscle of goldfish or carp. For each freely moving fish, an electromyogram (EMG) was recorded using the electrodes. In those fish paralyzed with curare, using the same electrode set, bursts of electrical activities consisted of spikes of smaller amplitude and of shorter duration compared with those recorded by EMG. Simultaneous recording of the extracellular activity and intracellular recording from the muscle revealed that the bursts of spikes recorded in the paralyzed fish were motor nerve impulses innervating the muscle and are considered to be fictive swimming activity. The method developed in the present study provides a useful tool with which to investigate neuronal mechanisms underlying swimming activity in teleost fish.