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1 Psychology, Amherst College, Amherst, Massachusetts, United States
2 United States; Psychology, Amherst College, Amherst, Massachusetts, United States
* To whom correspondence should be addressed. E-mail: jpbaird{at}amherst.edu.
The effects of intracerebroventricular application of melanin-concentrating hormone (MCH) on licking for sucrose, quinine hydrochloride (QHCl), and water solutions were evaluated in two experiments. In Experiment 1, rats received 90-min access to sucrose and water solutions after MCH or vehicle microinjection to the third ventricle (3V). MCH increased intake largely through increases in the rate of licking early in the meal and in the mean duration of lick bursts, suggesting an effect on gustatory evaluation. Therefore, in Experiment 2, brief access tests were used with a series of sucrose and QHCl concentrations in order to behaviorally isolate the effects of ICV MCH on gustatory evaluation. MCH uniformly increased licking for all sucrose solutions, water, and weak concentrations of QHCl, however it had no effect on licking for the strongest concentrations of QHCl, which were generally avoided under control conditions. Thus, MCH did not produce non-specific increases in oromotor activity, nor did it change the perceived intensity of the tastants. We conclude that MCH enhanced the gain of responses to normally-accepted stimuli at a phase of processing after initial gustatory detection and after the decision to accept or reject the taste stimulus. A comparison of 3V NPY and MCH effects on licking microstructure indicated that these two peptides increased intake via dichotomous behavioral processes: while NPY suppressed measures associated with inhibitory feedback from the gut, MCH appeared instead to enhance measures associated with hedonic taste evaluation.
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J.-P. Baird, C. Rios, J. L. Loveland, J. Beck, A. Tran, and C. E. Mahoney Effects of hindbrain melanin-concentrating hormone and neuropeptide Y administration on licking for water, saccharin, and sucrose solutions Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2008; 294(2): R329 - R343. [Abstract] [Full Text] [PDF] |
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