TASTE PRESTIMULATION INCREASES THE CHORDA TYMPANI NERVE RESPONSE TO MENTHOL

Electrophysiological recordings of the summated response of the chorda tympani nerve to menthol stimulation of the tongue were obtained from 15 adult Sprague-Dawley rats. The chorda tympani nerve response to menthol was of short duration, ending within 2.5 s after stimulus onset, leaving the receptors in a state of insensitivity to subsequent menthol stimulation. Rinse durations with deionized-distilled water up to 10 min failed to bring the receptors back to their original prestimulus state. Although stimulation with menthol prevented taste receptors from responding to subsequent presentations of menthol, the chorda tympani nerve would respond normally to NaCl, NH4Cl, KCl, sodium acetate, glucose, citric acid, and quinine-HCI solutions. Prior stimulation with one of these taste solutions resulted in the recovery of the menthol response. The magnitude of the recovered menthol response depended on the magnitude of the phasic response elicited by the preceding taste stimulus. A general explanation involving possible reception and transduction mechanisms was offered to account for menthol's unexpected stimulatory effects on the chorda tympani nerve.