title: Melanin concentrating hormone induces hippocampal acetylcholine release via the medial septum in rats.
abstract: Among various actions of melanin concentrating hormone (MCH), its memory function has been focused in animal studies. Although MCH neurons project to various areas in the brain, one main target site of MCH is hippocampal formation for memory consolidation. Recent immunohistochemical study shows that MCH neurons directly project to the hippocampal formation and may indirectly affect the hippocampus through the medial septum nucleus (MS). It has been reported that sleep is necessary for memory and that hippocampal acetylcholine (ACh) release is indispensable for memory consolidation. However, there is no report how MCH actually influences the hippocampal ACh effluxes in accordance with the sleep-wake cycle changes. Thus, we investigated the modulatory function of intracerebroventricular (icv) injection of MCH on the sleep-wake cycle and ACh release using microdialysis techniques. Icv injection of MCH significantly increased the rapid eye movement (REM) and non-REM episode time and the hippocampal, not cortical, ACh effluxes. There was a significant correlation between REM episode time and hippocampal ACh effluxes, but not between REM episode time and cortical ACh effluxes. Microinjection of MCH into the MS increased the hippocampal ACh effluxes with no influence on the REM episode time. It appears that the effect sites of icv MCH for prolongation of REM episode time may be other neuronal areas than the cholinergic neurons in the MS. We conclude that MCH actually increases the hippocampal ACh release at least in part through the MS in rats.
authors.affiliation: Department of Anesthesiology & Pain Medicine, Teikyo University School of Medicine, Tokyo, Japan.
authors.forename: Zhi-Hong
authors.initials: ZH
authors.lastname: Lu
authors.forename: Satoru
authors.initials: S
authors.lastname: Fukuda
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Minakawa
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yasuda
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Sakamoto
authors.forename: Shigehito
authors.initials: S
authors.lastname: Sawamura
authors.forename: Hidenori
authors.initials: H
authors.lastname: Takahashi
authors.forename: Noriko
authors.initials: N
authors.lastname: Ishii
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism*; D007028:Hypothalamic Hormones / Q000502:physiology*; D008297:Male; D008543:Melanins / Q000502:physiology*; D010907:Pituitary Hormones / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012686:Septal Nuclei / Q000378:metabolism*; D012895:Sleep, REM
chemical_list: D007028:Hypothalamic Hormones; D008543:Melanins; D010907:Pituitary Hormones; C019463:melanin-concentrating hormone; D000109:Acetylcholine