Jaw opening reflex affected by electroacupuncture in rat.

In rats, the jaw opening reflex to tooth pulp stimulation was suppressed, but that to lower lip stimulation was scarcely affected by electroacupuncture stimulation of the forefoot. After transection of the spinal trigeminal nucleus at the obex level, the magnitude of the reflex to tooth pulp stimulation was greatly decreased and electroacupuncture was less effective on the pulp-evoked reflex. By contrast, the reflex activity to lower lip stimulation was not altered after the transection. The present study suggests that the site of action of electroacupuncture on the jaw opening reflex is in the caudal part of the spinal trigeminal nucleus and that pulp evoked jaw opening reflex is a presumed nocifensive response.