BEHAVIORALBIOLOGY 24, 457--466 (1978) Effects of Dietary Methionine Supplementation on Preferences for NaCI Solutions FRANK A. CATALANOTTO ~ Department of Pediatric Dentistry, School of Dental Medicine, University of Connecticut Health Center, Farmington, Connecticut 06032 Preferences for eight concentrations of sodium chloride were measured in 10 control rats, 10 rats fed a diet supplemented with 2.5% methionine, and 10 rats fed a diet supplemented with 2.5% methionine and 2% zinc sulfate. All rats received the applicable diet for 21 days before testing was initiated with a 48-hr, two-bottle preference paradigm. Results of the study indicated that rats supplemented with methionine alone had significantly greater preferences for the salt solutions than rats from either of the remaining groups. Dietary treatment did not affect total volume intake (milliliters per gram body weight), Further analysis of the separate water and sodium chloride solution volume intakes demonstrated that while all groups consumed essentially equivalent amounts of water, the rats supplemented with methionine alone consumed significantly increased amounts of the salt so- lutions, thus manifesting an increased percentage preference. The results indicate that methionine, a thiol-containing amino acid, can alter preferences for sodium chloride solutions and that this effect can be reversed by zinc supplementation. The etiology of this change in preference behavior may be related to either decreased gustatory sensitivity (mediated by zinc depletion and/or thiol supplementation) or to salt craving (mediated by kidney and/or adrenal dysfunc- tion). Previous studies have suggested an interaction among thiols (SH), trace metals, and gustatory function (Catalanotto, 1978). This interaction is presumably based upon an inhibitory role of SH which can be reversed by certain trace metals (Henkin and Bradley, 1969). Yur'eva (1957, 1960, 1961, 1967, 1968) first demonstrated this participation of protein SH groups in the taste process by blocking such groups with cadmium chloride and depressing peripheral nerve activity; conversely, releasing SH groups with guanidine increased taste sensitivity. E The author was supported in part by U.S. Public Health Service Research Career Development Award 1 KO4 DE-00012. This research was supported by grants from the University of Connecticut Research Foundation. I wish to thank P. Lacy and K. Hesse for technical help, E. Meunster for statistical help, and Dr. E. Kremer and J. Shaw for editorial assistance. 457 0091-6773/78/0244-0457502.00/0 Copyright © 1978 by Academic Press, Inc. All rights of reproduction in any form reserved.