Peripheral afferent nerve impulses for conveying electroacupuncture effects on the jaw opening reflex evoked by tooth pulp stimulation in rat.

Effects of conditioning electrical stimulation of the nerves innervated around the meridian Ho-Ku point on the tooth-pulp evoked jaw opening reflex were investigated in Wistar albino rats. Changes of the threshold of the reflex were monitored before and after the conditioning stimulation. The increased changes of the threshold value gradually appeared and even after the cessation of the conditioning stimulation, its effect remained for several minutes. Of the three nerves in the brachial plexus (radial, median and ulnar), radial nerve was the most effective. The ipsilateral nerve stimulation was more effective on the threshold elevation of the reflex than the contralateral one. When the two nerves were stimulated simultaneously, the increase of the threshold value was sometimes observed as compared to the case of stimulating each nerve separately. However, in cases of the combination stimulation including radial nerve, the summation among the different impulses produced by the conditioning stimulation was scarcely observed; therefore, the effect was not reinforced.