Activity of alpha and gamma extensor motor axons during metrazol-induced seizures in cat

Abstract

Efferent discharges were recorded in nerves to extensor and flexor muscles simultaneously with EEG of contralateral motor area during Metrazol-induced seizures in anesthetized and curarized cats. Extensor motoneurons are much less active than flexors during typical EEG seizures. Unlike the flexor neurons α and γ extensor motoneurons are activated separately, without clear temporal relation between their discharges and electrocortical symptoms. Fusimotor activity of extensors increases only after the end of the cortical seizure. Convulsive activation of α and γ extensor motoneurons is often stronger in the absence of EEG paroxysmal waves than during a seizure. These observations suggest that convulsive activity of extensor motoneurons is not directly dependent on epileptic phenomena occurring in the motor cortex and extensor activation seems more likely connected to extrapyramidal projections of the epileptic process.