title: Changes of brain monoamine levels and physiological indexes during heat acclimation in rats.
abstract: Brain monoamines, such as noradrenaline (NA), dopamine (DA), and serotonin (5-HT), regulate many important physiological functions including thermoregulation. The purpose of this study was to clarify changes in NA, DA, and 5-HT levels in several brain regions in response to heat acclimation while also recording body temperature (Tb), heart rate (HR), and locomotor activity (Act). Rats were exposed to a heated environment (32°C) for 3h (3H), 1 day (1D), 7 days, 14 days (14D), 21 days, or 28 days (28D). After heat exposure, each of the following brain regions were immediately extracted and homogenized: the caudate putamen (CPu), preoptic area (PO), dorsomedial hypothalamus (DMH), frontal cortex (FC), and hippocampus (Hip). NA, DA, and 5-HT levels in the extract were measured by high performance liquid chromatography. Although Tb increased immediately after heat exposure, it decreased about 14D later. HR was maintained at a low level throughout heat exposure, and Act tended to increase near the end of heat exposure. After 3H, we observed a marked increase in NA level in the CPu. Although this response vanished after 1D, the level increased again after 28D. DA level in the CPu decreased significantly from 1D to 28D. 5-HT level in the PO and DMH decreased from 1D to 14D. It returned to control levels after 28D with increment of DA level. 5-HT level in the FC decreased at the start of heat exposure, but recovered after 28D; a time point at which DA level also increased. Monoamine levels in the Hip were unchanged after early heat exposure, but both 5-HT and DA levels increased after 28D. These results provide definitive evidence of changes in monoamines in individual brain regions involved in thermoregulation and behavioral, cognitive, and memory function during both acute and chronic heat exposure.
authors.affiliation: Graduate School of Community and Human Services, Rikkyo University, 1-2-26 Kitano, Niiza, Saitama 352-8558, Japan.
authors.forename: Hikaru
authors.initials: H
authors.lastname: Nakagawa
authors.affiliation: Graduate School of Community and Human Services, Rikkyo University, 1-2-26 Kitano, Niiza, Saitama 352-8558, Japan.
authors.forename: Takeru
authors.initials: T
authors.lastname: Matsumura
authors.affiliation: Graduate School of Community and Human Services, Rikkyo University, 1-2-26 Kitano, Niiza, Saitama 352-8558, Japan.
authors.forename: Kota
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Graduate School of Community and Human Services, Rikkyo University, 1-2-26 Kitano, Niiza, Saitama 352-8558, Japan.
authors.forename: Chisa
authors.initials: C
authors.lastname: Ninomiya
authors.affiliation: Graduate School of Community and Human Services, Rikkyo University, 1-2-26 Kitano, Niiza, Saitama 352-8558, Japan. Electronic address: ishiwata@rikkyo.ac.jp.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ishiwata
mesh_terms: D000064:Acclimatization; D000818:Animals; D001831:Body Temperature; D001833:Body Temperature Regulation; D001921:Brain / Q000502:physiology*; D001923:Brain Chemistry; D004298:Dopamine / Q000032:analysis / Q000378:metabolism*; D006339:Heart Rate; D018869:Heat-Shock Response; D006358:Hot Temperature; D008124:Locomotion; D008297:Male; D009638:Norepinephrine / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000032:analysis / Q000378:metabolism*
chemical_list: D012701:Serotonin; D004298:Dopamine; D009638:Norepinephrine
keywords: Body temperature; Dopamine; Heart rate; Heat acclimation; Noradrenaline; Serotonin