LATERAL RECTUS WHOLE MUSCLE AND MOTOR UNIT CONTRACTILE MEASURES WITH THE EXTRAOCULAR-MUSCLES INTACT

Both extracellular and intracellular stimulation of single motoneurons were shown to be similarly effective and consistent in eliciting cont ractile responses in single lateral rectus muscle motor units. The who le muscle was activated by stimulating the sixth nerve in the brain st em. Both whole muscle and motor unit contractile characteristics, unde r isometric conditions, were found to remain consistent regardless of whether this extraocular muscle was detached or left attached to the g lobe. In addition, whole muscle twitch and maximum tetanic tension evo ked by sixth nerve stimulation was significantly less than would be pr edicted by the linear summation of individual motor unit twitch and ma ximum tetanic tensions. (C) 1997 Elsevier Science B.V.