Facial nerve sensory responses recorded from the geniculate ganglion ofGallus gallus var.domesticus

Summary The extracellular responses of single sensory afferent cell bodies were recorded from the geniculate ganglion of the chicken following chemical, mechanical and thermal stimulation of the oral cavity using glass coated tungsten microelectrodes. Forty eight chemoreceptive units were identified from the anterior and posterior palate, and from the anterior mandibular area of the lower jaw. Their response characteristics to tyrode Ringer solution, distilled water, 0.05M hydrochloric acid, 0.5M sodium chloride, 1M fructose and 0.05M quinine hydrochloride were investigated. Only 5 units responded to a single stimulus and all of the other units responded to 2 or more stimuli. Thirty seven of the units which did not show single stimulus specificity did however respond best to one of the stimuli tested. The firing rates of these chemoresponsive units was slow, they showed little or no spontaneous activity and showed variable response patterns.Rapidly adapting and slowly adapting mechanoreceptors were also identified together with thermoreceptors (cold and warm units) and ear units.The results show that the facial nerve plays the major role in gustatory physiology of the chicken and these results are discussed in relation to the mammalian gustatory system.Abbreviations AMA anterior mandibular area - AP anterior palate - PP posterior palate - QHCl quinine hydrochloride