Development of an In-Vivo Model to Record Motor Neuron Activity in the Awake, Behaving Rat

The purpose of this study was to develop an in-vivo model to record motor neuron (MN) activity in the awake, behaving rat. This model is necessary for subsequent studies in which specific ion channels, thought to regulate MN activity, will be blocked pharmacologically while rats perform voluntary motor tasks. Rats were comfortably secured in an apparatus with their hind paw connected to a force transducer. Using operant conditions, they were trained to make controlled, voluntary contractions of the tibialis anterior, an ankle dorsiflexor. Once trained, activity was successfully recorded during the voluntary task from 20 motor units in 2 rats using intramuscular microelectrodes. The average firing rate of these units was 54 ± 12 impulses/s, substantially higher than equivalent recordings made from human biceps brachii muscle (14.8 ± 2 impulses/s). Therefore, this system provides a working in-vivo model for recording motor neuron activity in the awake, behaving rat that can be used for numerous studies in the future