Hynstrom et al. (2007)

Intrinsic electrical properties of spinal motoneurons vary with joint angle.

AS Hyngstrom, MD Johnson, JF Miller, CJ Heckman.

The dendrites of spinal motoneurons amplify synaptic inputs to a marked degree through persistent inward currents (PICs). Dendritic amplification is subject to neuromodulatory control from the brainstem by axons releasing the monoamines serotonin and norepinephrine; however, the monoaminergic projection to the cord is diffusely organized and does not allow independent adjustment of amplification in different motor pools. Using in vivo voltage-clamp techniques, here we show that dendritic PICs in ankle extensor motoneurons in the cat are reduced about 50% by small rotations (+/-10 degrees ) of the ankle joint. This reduction is primarily due to reciprocal inhibition, a tightly focused input shared only among strict muscle antagonists. These results demonstrate how a specific change in limb position can regulate intrinsic cellular properties set by a background of diffuse descending neuromodulation. - Nat Neurosci (2007) vol. 10 (3) pp. 363-9