[Effects of trigeminal stimulation on the vagal ambiguus neurons]

To elucidate the relationship between trigeminal stimulation and vagal ambiguus nucleus, effects of trigeminal stimulation on the changes infiring pattern of neurons in the ambiguus nucleus were examined. Unit discharges from the ambiguus nucleus in cats were recorded using a glass micropipette containing fast green FCF, and the microelectrode position was assertained histologically after the experiment. The analysis of unit discharges was performed with an ATAC-450 microcomputer. There were three types of neurons in the ambiguus nucleus from the view-point of effect of trigeminal stimulation: neurons for which firing was accelerated by trigeminal stimulation, neurons for which firing was decreased by trigeminal stimulation and neurons indifferent to trigeminal stimulation. These findings suggest that trigeminal stimulation modifies the neuronal firing pattern and consequently causes changes in vagal outflow, finally evoking the Reilly phenomenon in oral medicine.