The reinnervation of the tongue and salivary glands after lingual nerve injuries in cats.
The recovery of fibres in the chorda tympani and lingual nerves has been investigated in cats following nerve injury by recording the receptor properties of gustatory, thermosensitive and mechanosensitive units and the return of vasomotor and secretomotor responses. The combined trunk of the chorda tympani and lingual nerves was either crushed (4 animals) or sectioned (3 animals) unilaterally and recovery allowed for 12 weeks. After nerve crush, integrated whole nerve activity recorded from the chorda tympani during stimulation of the tongue with gustatory or thermal stimuli revealed a response profile which was similar to controls. After nerve section little or no activity could be recorded. Recordings made from 52 single units in the chorda tympani after nerve crush revealed that the proportions of gustatory, thermosensitive and mechanosensitive units were similar to those of controls. The units had slower conduction velocities, responded less vigorously and to a narrower range of stimuli. Recordings made from 46 units in the chorda tympani after nerve section revealed very few gustatory or thermosensitive units, the majority were purely mechanosensitive and the decrease in conduction velocity was greater than after nerve crush. Electrical stimulation of efferent vasodilator fibres in both the chorda tympani and lingual nerves, evoked a temperature rise on the dorsal surface of the tongue. This effect was completely restored after nerve crush but was significantly smaller after nerve section. The flow rate of saliva from the submandibular salivary gland was not significantly changed by nerve crush but was significantly smaller after nerve section. There was no evidence for functional reinnervation of gustatory or secretomotor terminals by inappropriate fibre types.
Robinson
P P
PP
Department of Physiology, Birmingham University Medical and Dental School, U.K.
D000200:Action Potentials; D000818:Animals; D002415:Cats; D002814:Chorda Tympani Nerve / Q000502:physiology; D004558:Electric Stimulation; D008036:Lingual Nerve / Q000502:physiology*; D008340:Mandibular Nerve / Q000502:physiology*; D009416:Nerve Regeneration; D009431:Neural Conduction; D012469:Salivary Glands / Q000294:innervation* / Q000378:metabolism; D014059:Tongue / Q000294:innervation*