[Regulation of the function of gamma- and alpha-motor neurons of antagonist muscles during cold tremor in the cat].

The impulse activity of flexor and extensor gamma- and alpha-motoneurons was investigated on anesthetized cats during cold tremor. It is found that total cooling, local cold stimulation of thermoreceptors or electrical stimulation of dorsomedial area of posterior hypothalamus evoke primary activation of flexor- and simultaneous inhibition of extensor gamma-motoneurons with secondary activation of flexor alpha-motoneurons. The electrical stimulation of the medial preoptic area during cold tremor causes primary inhibition of flexor alpha-motoneurons. It is concluded that activation of gamma-motoneuron precedes the development of cold tremor. The application of the described natural model for studying the role of the fusimotor system in the motoneuron regulation during postural activity is proved.