title: Diurnal rhythms of 5-HT1A and 5-HT2 receptor binding in euthermic and torpor prone deermice, Peromyscus maniculatus.
abstract: Deermice display both spontaneous and induced daily torpor bouts, attaining minimum body temperatures of 15-20 degrees C. There is evidence that brain serotonin may be involved in the initiation and/or maintenance of torpor. Inhibition of serotonin [5-hydroxytryptamine (5-HT)] synthesis markedly reduces the duration and depth of torpor. Because a certain percentage of deermice will not enter torpor under any circumstances, we were able to compare 5-HT receptor subtypes in deermice that readily enter into torpor (TP) and in non-torpor prone (NTP) animals. Deermice were trapped in the wild and subjected to food rationing and low ambient temperature and then sacrificed either in a normothermic or torpid state at 11:00 p.m. or 11:00 a.m. Whole brain was assayed for 5-HT1A and 5-HT2 receptor differences using [3H]8-OH-DPAT and [3H]ketanserin, respectively. The Bmax values for 5-HT1A receptors were significantly greater in both TP and NTP animals sacrificed at 11:00 p.m. compared to animals sacrificed at 11:00 a.m. In contrast, the density of 5-HT2 receptors was significantly greater in animals sacrificed at 11:00 a.m. compared to animals sacrificed at 11:00 p.m. This is consistent with the opposing functions of these receptors in the regulation of temperature and sleep. The affinity (Kd) of each receptor was unchanged. A comparison of TP and NTP animals sacrificed at the same time of day revealed no significant differences in either Bmax or in Kd values, indicating that differences in 5-HT1A and 5-HT2 receptors may not explain the heterogeneity of deermice in their ability to enter torpor.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Laboratory of Neurogenetics, NIAAA, NIH Clinical Center, Bethesda, MD 20892.
authors.forename: B A
authors.initials: BA
authors.lastname: Hulihan-Giblin
authors.forename: E B
authors.initials: EB
authors.lastname: Pivorun
authors.forename: D
authors.initials: D
authors.lastname: Goldman
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000378:metabolism; D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology*; D001923:Brain Chemistry / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D004435:Eating / Q000502:physiology; D007202:Indicators and Reagents; D007650:Ketanserin / Q000378:metabolism; D007700:Kinetics; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D010542:Peromyscus; D011869:Radioligand Assay; D011985:Receptors, Serotonin / Q000378:metabolism*; D012890:Sleep / Q000502:physiology
chemical_list: D007202:Indicators and Reagents; D011985:Receptors, Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D007650:Ketanserin