Figure 1. Schematic drawing of the experimental setting. (A) Barbiturate-anesthetized rats had their heads fixed to a stereotaxic frame in the left lateral decubitus. The masseteric nerve was exposed, hooked to an electrode, and preserved in a pool of liquid paraffin. A thread was attached to the mandible, and the masseter muscle was passively stretched by pulling the jaw open. (B) Sinusoidal stretch stimulation was applied with a maximum opening distance of 7.0 mm and a cycle duration of 4.0 sec (jaw-opening and -closing time of 2.0 seconds, followed by an interval of 2.0 sec). For data analysis, the stimulation (jaw-opening/-closing period) was divided into 3 phases (phases 1 to 3).