LOCATION OF NEURONS INNERVATING TENDON SPINDLES OF MASTICATOR MUSCLES

Spontaneous and evoked unitary potentials were recorded from the trigeminal mesencephalic nucleus of cats under chloralose anesthesia. The abundant spontaneous activity in the nucleus was ascribed primarily to the potentials arising from muscle spindles. These potentials were silenced by contraction of the muscles of mastication and resumed firing as the muscles relaxed. During the silent period of the muscle spindles, potentials arising from the tendon spindles were identified. These latter potentials were activated by increased tension in the muscles and occurred most frequently during the rising phase of the tension. Potentials from both the muscle spindles and tendon spindles were recorded from single loci in the nucleus. I conclude that cell bodies of the afferent neurons from the tendon spindles of the muscles of mastication are located in the mesencephalic nucleus in the cat. © 1969.