[Intercostal muscle motor unit activity during shivering].

The activity of single motor units of the intercostal muscles has been studied during reactions of thermoregulation in cats. It has been shown that during shivering both respiratory and tonic units are functioning with a frequency of discharges of 5--12/sec. A marked increased in the quantity of active tonic motor units was revealed in shivering. During warming of the animal and cessation of shivering first the tonic units and then the respiratory ones ceased to discharge. The thermoregulatory function of the intercostal muscles seems to be achieved essentially by tonic motoneurons activated by cold stimulation.