Ralph J. Berger, Ph.D. - US grants

The objectives of this research proposal are to elucidate the regulatory mechanisms of circadian rhythms in metabolic rate and body temperature (Tb) during sleep and wakefulness in the pigeon. The working hypothesis is that nocturnal Tb is regulated during sleep at a level proportional to the bird's energy reserves. This Continuation Proposal has two specific aims: (1) To investigate whether the proportional regulation of Tb and metabolic rate is sleep-dependent or under a circadian control independent of sleep itself, since the circadian rhythms of Tb and MR could be synchronized with those of sleep through a mutual entertainment by the light-dark cycle. To evaluate these alternate hypotheses, pigeons will be subjected to three different photoperiods: (a) 12:12 light-dark cycle (LD), (b) continuous dim red light (DD), and (c) continuous bright light (LL) presented in a schedule of five consecutive conditions: LD, 21 days; LL, 21 days; DD, 21 days; LL 21 days; LD 2 days. Birds will also be subjected to a 4-day fast during the first three conditions. Tb, body weight (BW), behavioral activity (ACT) and feeding (F) will be continuously recorded, and 24-hr electrophysiological recordings taken at frequent intervals. Raster and spectral plots of Tb, BW, ACT, F and sleep stages in each condition will be compared. Stages of sleep and EEG Fourier spectral analyses will be compared between nutritional and photoperiodic conditions, and across transitions from LL to DD and from LL to LD to assess possible compensatory recovery of sleep after extended wakefulness in LL. (2) To explore the potential roles of melatonin and beta-hydroxybutyrate (beta-OHB) as metabolic regulatory factors involved in the control of the circadian rhythms of sleep and Tb. Pigeons provided with ad lib food and water will be exposed to LL until circadian rhythms of TB and sleep have disappeared. i.v. infusions of melatonin will then be administered for 12- hr periods each day to determine whether melatonin reinstates and entrains circadian rhythms of Tb and sleep. Control infusions of saline will be administered subsequently. Circadian patterns of serum concentrations of beta-OHB -- a ketone metabolite of lipolysis -- will be assayed during 4- day fasts in pigeons exposed to a LD. These proposed experiments should further delineate a model of circadian regulation of Tb and sleep. Establishment of additional physiological homologies between sleep, circadian torpor and hibernation should elucidate sleep functions, and might lead to clinical applications in the treatment of disorders of sleep and regulation of body weight, diabetes, and depression.

The objectives of this research proposal are to elucidate the regulatory mechanisms of circadian rhythms in metabolic rate and body temperature (Tb) during sleep and wakefulness in the pigeon. The working hypothesis is that nocturnal Tb is regulated during sleep at a level proportional to the bird's energy reserves. This Continuation Proposal has two specific aims: (1) To investigate whether the proportional regulation of Tb and metabolic rate is sleep-dependent or under a circadian control independent of sleep itself, since the circadian rhythms of Tb and MR could be synchronized with those of sleep through a mutual entertainment by the light-dark cycle. To evaluate these alternate hypotheses, pigeons will be subjected to three different photoperiods: (a) 12:12 light-dark cycle (LD), (b) continuous dim red light (DD), and (c) continuous bright light (LL) presented in a schedule of five consecutive conditions: LD, 21 days; LL, 21 days; DD, 21 days; LL 21 days; LD 2 days. Birds will also be subjected to a 4-day fast during the first three conditions. Tb, body weight (BW), behavioral activity (ACT) and feeding (F) will be continuously recorded, and 24-hr electrophysiological recordings taken at frequent intervals. Raster and spectral plots of Tb, BW, ACT, F and sleep stages in each condition will be compared. Stages of sleep and EEG Fourier spectral analyses will be compared between nutritional and photoperiodic conditions, and across transitions from LL to DD and from LL to LD to assess possible compensatory recovery of sleep after extended wakefulness in LL. (2) To explore the potential roles of melatonin and beta-hydroxybutyrate (beta-OHB) as metabolic regulatory factors involved in the control of the circadian rhythms of sleep and Tb. Pigeons provided with ad lib food and water will be exposed to LL until circadian rhythms of TB and sleep have disappeared. i.v. infusions of melatonin will then be administered for 12- hr periods each day to determine whether melatonin reinstates and entrains circadian rhythms of Tb and sleep. Control infusions of saline will be administered subsequently. Circadian patterns of serum concentrations of beta-OHB -- a ketone metabolite of lipolysis -- will be assayed during 4- day fasts in pigeons exposed to a LD. These proposed experiments should further delineate a model of circadian regulation of Tb and sleep. Establishment of additional physiological homologies between sleep, circadian torpor and hibernation should elucidate sleep functions, and might lead to clinical applications in the treatment of disorders of sleep and regulation of body weight, diabetes, and depression.

The hypothesis that slow wave sleep (SWS) is a thermoregulatory process counteracting hypothermia and conserving energy expenditure will be tested by determining whether putative manipulations of human brain temperature (Tbr), by heating and cooling the face, influence the propensity for SWS (stages 3+4). Since Tbr cannot be directly measured in human subjects, tympanic temperature (Tty) will serve as a practical index of Tbr. Rectal temperature (Tre) and skin temperature of the foot (Tft) will also be recorded. In each of two experiments, nine Ss will be studied, each for eight nights. Following two adaptation nights to the apparatus and laboratory, they will be subjected to two nights in each of three condition : baseline, facial heating and facial cooling. A Latin square design will counterbalance the order of conditions across Ss. In one experiment therma manipulations will begin 30 min prior to lights out and continue throughout the night. In the other they will be restricted to the last 3 hr of the night--a period when SWS is normally absent. Electrophysiological records (EEG, EOG and EMG) will be visually scored for stages of sleep and wakefulness, and EEG slow wave activity will be analyzed with a computer using fast Fourier spectral analysis. Hourly and nightly mean values of Tty, Tre, Tft, SWA and sleep stage variables will be compared between conditions in each experiment by paired differences t-tests. Pearson product-moment correlations will be computed hourly SWA and Tty, Tre, Tft for each S across all nights in each experimen , and an average r across Ss after a Z transformation. Similar correlations will be computed between SWS (stages 3 + 4) and Tb measures, and between other sleep stages and Tb measures. The experiments should elucidate the biological functions of sleep, by testing whether the propensity for SWS is related to Tbr. They may also le d to clinical applications in thermal treatment of sleep disorders--especiall insomnia. Low amounts of stage 4 SWS and minimal decreases in rectal temperature during sleep are characteristic of depressed patients compared with control subjects. Therefore, alterations in heat balance might also prove effective in the treatment of depression.

9417375 Berger This award will partially support the travel expenses for Dr. Ralph Berger of the Department of Biology, University of California, Santa Cruz, to enable him to travel to Tasmania, Australia to conduct cooperative research with Dr. Stewart Nicol of the Department of Physiology at the University of Tasmania in Hobart, Australia. The cooperative work will focus on a study of sleep in the echidna (Tachyglossus aculeatus), a primitive egg-laying mammal unique to Australia. Current evolutionary theory of sleep maintains that slow wave sleep evolved in conjunction with endothermy (metabolic heat production), while rapid eye movement sleep (REM) emerged later in early ancestors of marsupial and placental mammals. This project will examine sleep in young echidnas at an ambient temperature and in a light/dark cycle similar to their natural habitat. Dr. Nicol has performed comparative thermoregulatory and metabolic studies on echidnas for several years; Dr. Berger contributes expertise in the comparative electrophysiology of sleep. In addition to the evolutionary significance of this project, information from the study may aid in the conservation and management of echidnas and other primitive mammals.