[Importance of the degeneration of afferent components of the hypoglossal nerve on the reflex activity of the nucleus of the hypoglossal nerve in the frog].

The section of frog XII cranial nerve facilitates the reflex activity given by its nucleus. Since this positive effects is not dependent upon any motoneurons degeneration, the hypothesis has been put forward that only the afferent component of the XII nerve is able to modulate the reflex activity by means of PAD effect at the solitarius nucleus. This hypothesis has been tested examining the effect both on the glossopharyngeal reflex response and on the DRR following excision respectively of the dorsal root and of the whole hypoglossal nerve. In preparations with a XII dorsal root transected, electrical stimulation of the homolateral glossopharyngeus nerve evoked a much more intense reflex response than at the intact side. The same effect was evident after the section of the whole nerve.