Type of Document	Thesis
Author	Vaughn, Joanne M.
Author's Email Address	joannevaughn@gmail.com
URN	etd-11072006-161209
Title	Behavioral and Electrophysiological Taste Responses Change Following Brief and Prolonged Dietary Sodium Deprivation
Degree	Master of Science
Department	Psychology, Department of
Advisory Committee	Advisor Name Title Robert Contreras Committee Chair Elaine Hull Committee Member Mark Licht Committee Member
Keywords	Salt Appetite Gustatory Responses Chorda Tympani Nerve Amiloride Sodium Deprivation
Date of Defense	2006-10-26
Availability	unrestricted
Abstract Sodium (Na+) is an essential mineral required in many body processes including fluid balance, neural conduction, cell membrane transport, muscle contraction, enzymatic function, and blood pressure maintenance. Dietary Na+ deprivation elicits a hormonal response to promote sodium conservation, and a behavioral response to increase sodium ingestion. It has generally been accepted that the former occurs within 24-h after sodium deprivation, while the latter is delayed and may not appear until as long as 10 d later. Na+ deprivation of similar duration also decreases the sensitivity of the chorda tympani nerve (CT) to NaCl, suggesting that changes in CT responses are necessary for increased NaCl intake. However, recent work from our laboratory showed that, in short term tests, licking responses to NaCl solutions increased following only two days of Na+ deprivation, suggesting a rapidly occurring change in NaCl taste responses. Accordingly, the following experiments were designed to accomplish two primary goals. The first experiment used microstructural analysis to examine patterns of NaCl consumption after two days of Na+-deficient diet. The goal of the second experiment was to determine whether brief dietary Na+ deprivation decreases CT responses to NaCl, and to assess CT amiloride-sensitivity after brief (2 days) or prolonged (10 days) dietary Na+ deprivation. The obtained results show 24-h intakes did not differ; however patterns of ingestion were altered by two days of Na+ deprivation. Na+-deficient rats licked significantly more during the first NaCl intake bout compared to control rats, but the two groups had comparable numbers of licks for the remaining NaCl bouts. CT responses to NaCl were reduced at all concentrations after both brief and prolonged Na+ deprivation compared to Na+-replete controls. Moreover, amiloride, which suppressed CT responses to NaCl by approximately 30% in controls, had virtually no effect on CT responses in Na+-deprived rats. These results show that two days of Na+ deprivation are sufficient to alter patterns of ingestion of concentrated NaCl and provide further support for early changes in gustatory responses after brief dietary Na+ deprivation. Furthermore, these results suggest that both brief and prolonged Na+ deprivation lead to changes in CT responses to NaCl that may selectively involve the amiloride-sensitive component of NaCl taste.
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