Lateral Ventricular Injections of the NK 3 Agonist Senktide Affect Salt Taste-Elicited Responses

Abstract

Flynn, F. W. and M. E. Smith. Lateral ventricular injections of the NK 3 agonist senktide affect salt taste-elicited responses. Peptides 19(2) 319–324, 1998.—Central injections of the selective tachykinin NK 3 receptor agonist senktide (SENK) suppresses salt appetite. Also, following SENK, intraoral infusions of hypertonic NaCl elicit fewer ingestive taste reactivity responses and more aversive responses than following intraventricular injections of isotonic saline. This pattern of taste reactivity results suggest that SENK affects the oral stimulating properties of salt taste. Before accepting this interpretation, however, alternative explanations need to be examined. The following experiments evaluated whether the effects of intraventricular SENK injection on taste reactivity could be due to: 1) a general oral motor impairment that reduces ingestive responding to tastes (Experiment 1) or; 2) SENK having aversive consequences (Experiment 2). In Experiment 1, the effects of intraventricular injections of SENK (200 ng) on taste reactivity responses to 0.5 M NaCl and 0.1 M sucrose were measured in sodium deficient rats. Intraoral infusions of 0.5 M NaCl elicited fewer ingestive taste reactivity responses following SENK than injections of isotonic saline in sodium deficient rats. Sucrose continued to elicit the same high number of ingestive taste reactivity responses following intraventricular injections of isotonic saline and SENK. Thus, SENK did not cause a general decrease in ingestive responding. A conditioned taste aversion test was employed in Experiment 2 to determine if SENK had aversive consequences. Rats were given 30 min access to alanine (0.3 M) and were then administered either lithium chloride (LiCl) or intraventricular injections of SENK (200 ng) on three consecutive days. Rats avoided alanine that was paired with LiCl, but those rats that had alanine paired with SENK showed no avoidance of the taste even after three pairings. These results replicate findings that intraventricular injections of the NK 3 agonist SENK decreases the palatability of NaCl (as measured by taste reactivity) and suggest that its effect on NaCl-elicited taste reactivity is not due to the treatment causing a motor impairment or malaise.