Analysis of amiloride inhibition of chorda tympani taste response of rat to NaCl

Abstract
The kinetics of inhibition by amiloride of the integrated chorda tympani response were investigated in rats subjected to lingual stimulation with NaCl. In one series of experiments the time of exposure to amiloride was varied at fixed amiloride concentration. Exposure to 10(-4) M amiloride for 2 s reduced the response to 0.5 M NaCl by approximately 50%. The time course of recovery from amiloride inhibition was first order (relaxation time approximately equal to 4 min) for all exposure times. For exposure to 10(-4) M amiloride for less than or equal to 30 s recovery was better than 90% in 20 min. Not all of the chorda tympani response was inhibited by amiloride. With 0.5 M NaCl there was a 70% reduction in response, whereas at 0.05 M NaCl the reduction was only 30%. Parallel effects of amiloride were seen in the short-circuit current of an in vitro preparation of canine lingual epithelium. Amiloride reduced the short-circuit current by the same percentage as it inhibited the chorda tympani response. These results suggest that gustatory transduction is mediated in part by an apical membrane transport system that can be inhibited by amiloride. There exists, however, a second transducing element that is amiloride insensitive. A model is developed, assuming, in part, that the neural response reflects the flows of Na through amiloride-sensitive apical pathways.