Presentation Details
| TRPM8 participates in conditioned preferences for oral and ingesta temperatures in mice Kyle T.Zumpano, Christian H.Lemon. University of Oklahoma, Norman, OK, USA |
Abstract
Here we studied if innate preferences for oral temperatures in mice can change when paired with calories and the role of TRPM8 in recognition of conditioned temperatures. Water-restricted C57BL/6J mice (B6, n = 6) were trained on a 10-day conditioning procedure with 15°C 8% glucose (CS+) and 30°C water (CS-) in a custom contact thermo-lickometer. On interleaved days, mice were offered the CS+ or CS- thermal fluid over 30, 5-sec trials. B6 mice are innately indifferent to 15° and 30°C water in orosensory tests (our prior data). After training, water-replete mice entered testing with 15° and 30°C water in a brief-access fluid licking test. During testing, mice showed a preference for 15° over 30°C water (e.g., test day 2, sign rank test, p = 0.03), changing their innate indifference, that extinguished with further testing (test day 3, p = 1). A second squad of mice (B6, n = 8; TRPM8 knockout (-/-), n = 8) was trained with 30°C as the CS+ (8% glucose) and 15°C as the CS- (water). For testing, a third “catch” stimulus of 33°C water was added to determine if mice generalized a conditioned preference to 30°C (mild oral cooling) to warmer temperatures. Water-replete B6 and TRPM8-/- mice showed greater licking for 30° and 33° than 15°C water on the first two test days (Friedman’s ANOVAs; p <0.05). During test days 3 and 4, B6 mice were indifferent across temperatures (p > 0.5), and trended to show extinction and reduced licks to 33°C. In contrast, TRPM8-/- mice continued to lick more to 30° and 33° over 15°C (p <0.5), implying these mice are unable to discern the CS+ and catch temperatures. These data begin to show that innate oral thermal preference in mice can change with ingestive experiences and that TRPM8 is needed to discern fine differences between cool and warmer temperatures.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.