| Abstract: | Activity of flexor and extensor γ- and α-motoneurons during cold tremor was investigated in anesthetized cats. General hypothermia and local cold stimulation or electrical stimulation of the dorsomedial region of the posterior hypothalamus were shown to induce primary activation of flexor and simultaneous inhibition of activity of extensor γ-motoneurons, followed by activation of flexor α-motoneurons (extensor muscles are not involved in temperature regulating activity). Electrical stimulation of the medial preoptic region during cold tremor led to primary inhibition of flexor α-motoneuron activity. It is concluded from these results that the development of temperature-regulating muscular activity is preceded by activation of γ-motoneurons. The use of cold tremor induced in anesthetized cats as a natural model with which to study the role of the fusimotor system in regulation of function of motor nuclei during postural activity is argued. |
