Abstract
In order to determine the facial regions responsible for evoking the trigemino-neck reflex, the activity of the second cervical nerve innervating the dorsal neck muscles was investigated by electrically stimulating different facial afferent nerves of cats anesthetized with pentobarbital sodium. The infraorbital nerve trunk arising from the frontal part of facial skin was composed of several nerve fascicles with different receptive fields. An electrical stimulation of each fascicle elicited certain reflex discharges in the bilateral cervical nerves. All of these reflex responses had a low threshold and showed no differences in magnitude. With increasing stimulus intensity, the latency of these reflexes decreased, while both their amplitude and duration increased. Comparing the latencies under identical response magnitudes, the responses could be divided into two groups; one with a short latency elicited by the stimulation of the fascicles arising from the skin from the nose and another with a longer latency by those from the skin from the upper lip. These findings suggest that there are two groups of reflex responses, each corresponding to sensory inputs from different areas of the facial skin in the trigemino-neck reflex of cats.
