Effects of melanin-concentrating hormone on licking microstructure and brief-access taste responses.
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 to behaviorally isolate the effects of intracerebroventricular 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 nonspecific 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; although NPY suppressed measures associated with inhibitory feedback from the gut, MCH appeared instead to enhance measures associated with hedonic taste evaluation.
Baird
John-Paul
JP
Dept. of Psychology, Amherst College, Amherst, MA 01002, USA. jpbaird@amherst.edu
Rios
Catalina
C
Gray
Nora Elizabeth
NE
Walsh
Caroline Elizabeth
CE
Fischer
Shannon Glenora
SG
Pecora
Ashley Layne
AL
D000818:Animals; D004305:Dose-Response Relationship, Drug; D025461:Feedback, Physiological / Q000502:physiology; D005247:Feeding Behavior / Q000502:physiology*; D041981:Gastrointestinal Tract / Q000502:physiology; D007028:Hypothalamic Hormones / Q000494:pharmacology*; D007031:Hypothalamus / Q000502:physiology; D008297:Male; D008543:Melanins / Q000494:pharmacology*; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D009478:Neuropeptide Y / Q000494:pharmacology; D010907:Pituitary Hormones / Q000494:pharmacology*; D011803:Quinine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013395:Sucrose / Q000494:pharmacology; D013649:Taste / Q000187:drug effects / Q000502:physiology*; D014059:Tongue / Q000187:drug effects* / Q000502:physiology
D007028:Hypothalamic Hormones; D008543:Melanins; D009125:Muscle Relaxants, Central; D009478:Neuropeptide Y; D010907:Pituitary Hormones; D013395:Sucrose; C019463:melanin-concentrating hormone; D011803:Quinine