We have been studying neuronal mechanisms of oral functions such as jaw and tongue movement, gustation and salivary secretion. The present foci of our researches are as follows.
Masticatory force is greater when hard food is chewed than when soft food is chewed.
Such regulation of the masticatory force is conducted automatically according to the hardness of food. EMG activities of masticatory muscles and jaw movements, before and after deprivation of periodontal sensation. Masticatory force is measured with a small force-displacement transducer developed recently in our laboratory. In order to study the neuronal mechanisms controlling jaw movement, we record intracellular activities from trigeminal motoneurons in the brainstem slice preparation by using conventional intracellular recording or whole cell patch clamp methods. We found that the firing pattern of the motoneurons are greatly affected by both depolarizing and hyperpolarizing spike afterpotentials and that those potentials are differentially generated by calcium influx through different calcium channels.