Chorda tympani taste response of rat to hydrochloric acid subject to voltage-clamped lingual receptive field.

The chorda tympani nerve response of the rat to HCl was obtained with the lingual receptive field under voltage clamp. Unlike NaCl responses, HCl responses were not affected by inside positive voltage perturbations. However, HCl responses under negative voltage clamp were suppressed in contrast to NaCl responses, which were enhanced. Unlike NaCl responses, HCl responses were amiloride insensitive. HCl rinsing from the tongue produced a large off-response. At zero current clamp the off-response coincided with an anomalous increased positive potential. The paracellular resistance was also higher for HCl relative to the same concentration of NaCl. This is evidence that H+ binds to the normally fixed anionic sites of the paracellular pathway rendering it anion selective. It is postulated that release of bound H+ from surface buffer sites is responsible for the second burst of neural activity upon rising HCl. Acids stimulate primarily through the paracellular pathway, which also furnishes buffering sites that regulate H+ concentration, thereby protecting the sensory apparatus from hyperacidic conditions.