[Electrophysiological characteristics of muscle fibers in cold-adapted rats].

In rats, the membrane APs of single muscle fibers of fast (m. gastrocnemius) and slow (m. soleus) muscles were measured in cold--adapted animals and in a control group. In cold--adapted rats the membrane AP of slow muscle fibers was higher than in the control group, whereas in the fast muscle fibers the AP was decreased. The AP in cold--adapted rats fast muscle fibers was shorter and in the slow muscle fibers longer than in muscles of the control group. The data suggest that the excitation processes are changed in both types of muscles in cold--adapted rats.