[Inhibitory effect on crossed bands in the tongue mechanoreceptor innervation]

The inhibitory influence exercised at the bulbar level by crossed afferent innervation of the lingual mechanoreceptors has been examined in the frog. To reach this aim it has been electrically stimulated the central stump of both glossopharyngeal and hypoglossal unilaterally axotomized nerves and recorded the crossed reflex effects in the controlateral hypoglossal motoneurones. By comparison a similar reflex has been evoked by means of stimulation of intact glossopharyngeal and hypoglossal nerves in the same preparation. As regards the glossopharyngeal crossed afferences it has been observed that the stimulation of axotomized nerves intensifies controlateral reflex response, while stimulated intact afference produces an increased reflex only after controlateral hypoglossal section. This last kind of effect has been observed also in the case of a crossed innervation of the hypoglossal lingual afference. These results show a notable extension of lingual crossed mechanoreceptors innervation and indicate its ability to obtain complex contralateral inhibitory effects. This ability however is more evident as regards the glossopharyngeal nerve. These observations are useful in order to explain the properties of the same inhibitory influences exercised homolaterally by the mechanoreceptors afference.