| Abstract [eng] |
Motoneurons are the spinal neurons that directly control the muscle contraction. The gain characterizes how the synaptic input to motoneuron is converted in to action potential firing and subsequent muscle contraction. The high gain allows a high force and fast contraction, while the low gain is essential for a fine control of movements. The gain of motoneurons is mainly determined by a set of ion channels in membrane and therefore is a subject for modification. It is known, that the gain decreases during adaptation of action potential firing. Moreover, the neurotransmitters released during spinal network activity may modify the ion channel activity and therefore adjust the gain to the functional needs. The aim of this study was to evaluate the gain of spinal cord motoneurons and investigate mechanisms of its modification. Spinal motoneurons from adult turtle were used. We found that the gain of motoneurons estimated from triangular current ramps is the same as steady one obtained from square current steps. Pharmacologically increased conductance of motoneuron membrane does not change the gain. Finally, we demonstrated that persistent inward Na+ current increases excitability and reduces the transient and early gain of spinal motoneurons. |
