Relation between motoneuron position and lateral rectus motor unit contraction speed: an intracellular study in the cat abducens nucleus.

Thirty-one single muscle units of the cat lateral rectus muscle were activated through intracellular stimulation of their motoneurons in the principal abducens nucleus. Motoneurons encountered from dorsal to ventral in the nucleus tended to innervate muscle units with progressively slower contraction times. In addition, two cells innervated muscle units which did not exhibit twitch contractions and three cells innervated muscle units with unusually strong twitch contractions.