title: Neuropeptide-Y modulates eating patterns and masticatory muscle activity in rats.
abstract: Neuropeptide Y (NPY) is a powerful orexigenic peptide secreted by hypothalamic neurons. The present study investigates how NPY injection into the lateral ventricle modulates masticatory movements and eating behavior. Behavioral experiments showed that cumulative food intake over a 4-h period and latency to eating were increased and decreased, respectively, in NPY-injected rats compared to saline-injected control rats. The feeding time for 2 g pellets was shorter in NPY-injected rats and resulted in an increased feeding rate, with more potent effects observed at 1 μg compared to 10 μg NPY. After injection of 10 μg NPY, a greater number of bouts with shorter average bout duration for eating 2g, compared to 1 μg NPY, were observed. Furthermore, 10 μg NPY injection resulted in prolonged periods of moving and shortened sleep and grooming. Electromyography recordings from the digastric and masseter muscles showed two distinct patterns of bursts corresponding to the gnawing and chewing phases. After the injection of 1 μg NPY, the burst magnitude of masseter muscle during the gnawing phase increased, reflecting strong jaw-closing muscle activity. The relative integrated EMG of masseter muscle in both phases was smaller following injection of 10 μg NPY in comparison with that of 1 μg NPY. The present study indicates that 1 μg NPY administration promotes feeding behavior together with increased feeding rate and powerful jaw-closing muscle activity; whereas 10 μg NPY administration lowers jaw-closing muscle activity during biting and produces mastication with shorter and more frequent feeding bouts than 1 μg NPY.
authors.affiliation: First Department of Oral and Maxillofacial Surgery, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita City, Osaka 565-0871, Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Ushimura
authors.affiliation: First Department of Oral and Maxillofacial Surgery, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita City, Osaka 565-0871, Japan. Electronic address: g2787b@dent.osaka-u.ac.jp.
authors.forename: Tadataka
authors.initials: T
authors.lastname: Tsuji
authors.affiliation: First Department of Oral and Maxillofacial Surgery, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita City, Osaka 565-0871, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: First Department of Oral and Maxillofacial Surgery, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita City, Osaka 565-0871, Japan.
authors.forename: Mikihiko
authors.initials: M
authors.lastname: Kogo
authors.affiliation: Department of Health and Nutrition, Faculty of Health Science, Kio University, Koryo-cho, Nara 635-0832, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamamoto
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000187:drug effects; D005247:Feeding Behavior / Q000187:drug effects*; D007276:Injections, Intraventricular; D008297:Male; D008409:Mastication / Q000187:drug effects*; D008410:Masticatory Muscles / Q000187:drug effects*; D009478:Neuropeptide Y / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects
chemical_list: D009478:Neuropeptide Y; D000804:Angiotensin II
keywords: Behavioral analysis; Electrophysiology; Feeding; Mastication; Neuropeptide-Y; Orexin