Innervation of the rat tympanic membrane from the superior cervical and glossopharyngeal ganglia

True Blue and Fluorogold were applied to the external surface of the tympanic membrane and middle ear mucosa of Sprague-Dawley rats and neurons in the superior cervical and glossopharyngeal ganglia were labelled with these retrograde tracer dyes. Dye absorption was poor from the tympanic membrane unless the keratinised layer was damaged with crystalline silver nitrate prior to dye application. Stained neurons were scattered throughout the superior cervical ganglion with no evidence of somatotopy. Several neurons in the glossopharyngeal ganglion stained with both dyes when these had been simultaneously applied to both sites in single animals. There was no evidence of dual staining of neurons in the superior cervical ganglion.