AMILORIDE INHIBITS TASTE NERVE RESPONSES TO NACL AND KCL IN SPRAGUE-DAWLEY AND FISCHER-344 RATS

In a two-bottle test, Sprague-Dawley rats preferentially consume a gre ater amount of hypotonic and isotonic NaCl solutions relative to water , whereas inbred Fischer 344 (F344) rats fail to prefer NaCl solutions at any concentration relative to water. To determine whether taste co ntributes to this strain difference, we measured the integrated neural responses of the chorda tympani nerve to a concentration range of NaC l and KCl solutions. The amiloride-sensitive component of the taste ne rve response was assessed by adding amiloride during salt stimulation in Experiment 1, and by pretreating the taste receptors with amiloride prior to salt stimulation in Experiment 2. Adding amiloride to NaCl d uring sustained neural activity suppressed chorda tympani nerve respon ses more than pretreating the tongue with amiloride. Adding amiloride during salt stimulation also partially suppressed chorda tympani neuro n responses to KCl, a presumed control stimulus. The neural responses of the chorda tympani nerve to NaCl and KCl were similar for salt-avoi ding F344 and salt-preferring Sprague-Dawley rats. However, amiloride pretreatment suppressed the taste nerve responses to NaCl significantl y less in F344 rats than in Sprague-Dawley rats. The strain difference in the amiloride-sensitive component of the taste response may contri bute to the difference in NaCl preference.