The origin of short- and long-latency mylohyoid nerve responses elicited by high-intensity electrical stimulation of intradental nerve in cats.
A double reflex response of the mylohyoid nerve to the jaw depressor muscles after electrical stimulation of the intradental nerves was recorded in cats anaesthetized with alpha-chloralose. The threshold value of the long-latency (16-19 ms) response was almost 20 times greater than that of the short-latency (5-8 ms) response. At the threshold intensity of the long-latency response, the short-latency response with shorter latency appeared. After extirpation of the stimulated tooth pulp, the short-latency response with a lower threshold disappeared, whereas the short-latency response with a higher threshold and the long-latency response both persisted and showed no change in threshold or latency. These findings indicate that the low-threshold, short-latency response was due to excitation of pulpal nerve fibres, while the high-threshold, short-latency response and the long-latency response were both due to excitation of extrapulpal afferent fibres as a result of the spread of current outside the tooth.