Amiloride-sensitive signals and NaCl preference and appetite: a lick-rate analysis

Rats prefer hypotonic and isotonic NaCl solutions to water in long-access d rinking paradigms. To focus on the role of taste signals in NaCl preference , licking patterns of rats with 30-s exposure to NaCl solutions (0-0.5 M) w ere examined when they were either water deprived, sodium depleted, or not deprived (NaCl mixed in dilute sucrose). In all three conditions, rats disp layed a preference for NaCl. The addition of 100 mu M amiloride, a sodium c hannel blocker, to NaCl did not change rats' licking when they were sodium replete but dramatically reduced licking when they were deplete. Transectio n of the chorda tympani (CT) nerve, an afferent pathway for amiloride-sensi tive Na+ signals, had no effect on NaCl preference in nondeprived rats and only a modest effect on those that were Na+ deplete. Amiloride was found to exert significant suppression of NaCl intake in Na+-depleted rats with tra nsection of the CT, supporting the existence of other afferent pathways for transmission of amiloride- sensitive Na+ signalling. Together, these studi es argue for the involvement of different neural signalling mechanisms in N aCl preference in the presence and absence of explicit Na+ need.