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Truong VH, Myung J. LocoBox: Modular Hardware and Open-Source Software for Circadian Entrainment and Behavioral Monitoring in Home Cages. SENSORS (BASEL, SWITZERLAND) 2023; 23:9469. [PMID: 38067841 PMCID: PMC10708669 DOI: 10.3390/s23239469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 10/05/2023] [Accepted: 11/26/2023] [Indexed: 12/18/2023]
Abstract
Day-night locomotor activities are the most readily observed outputs of the circadian (~24-h period) clock in many animals. Temporal patterns of the light-dark schedule serve as input to the clock. While circadian activity patterns under various lighting conditions have been observed and documented, the full extent of circadian locomotor activities by genotype and entrainment remains uncharacterized. To facilitate large-scale, parallel cataloging of circadian input-output patterns, we created the LocoBox, an easy-to-construct and easy-to-operate system that can control environmental light with flexible entrainment scenarios combined with the T-cycle and measure locomotor activities in individual home cages. The LocoBox is made using economical, common components, and normal breeding cages can be used for long-term recording. We provide details of the components and blueprints, along with software programs for Arduino and a Python-based graphical user interface (GUI), so that the system can be easily replicated in other laboratories.
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Affiliation(s)
- Vuong Hung Truong
- Graduate Institute of Mind, Brain and Consciousness (GIMBC), Taipei Medical University, New Taipei City 235, Taiwan
- Brain and Consciousness Research Centre (BCRC), TMU-Shuang Ho Hospital, New Taipei City 235, Taiwan
| | - Jihwan Myung
- Graduate Institute of Mind, Brain and Consciousness (GIMBC), Taipei Medical University, New Taipei City 235, Taiwan
- Brain and Consciousness Research Centre (BCRC), TMU-Shuang Ho Hospital, New Taipei City 235, Taiwan
- Graduate Institute of Medical Sciences (GIMS), Taipei Medical University, Taipei 110, Taiwan
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2
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Walbeek TJ, Harrison EM, Gorman MR, Glickman GL. Naturalistic Intensities of Light at Night: A Review of the Potent Effects of Very Dim Light on Circadian Responses and Considerations for Translational Research. Front Neurol 2021; 12:625334. [PMID: 33597916 PMCID: PMC7882611 DOI: 10.3389/fneur.2021.625334] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 01/06/2021] [Indexed: 12/16/2022] Open
Abstract
In this review, we discuss the remarkable potency and potential applications of a form of light that is often overlooked in a circadian context: naturalistic levels of dim light at night (nLAN), equivalent to intensities produced by the moon and stars. It is often assumed that such low levels of light do not produce circadian responses typically associated with brighter light levels. A solid understanding of the impacts of very low light levels is complicated further by the broad use of the somewhat ambiguous term “dim light,” which has been used to describe light levels ranging seven orders of magnitude. Here, we lay out the argument that nLAN exerts potent circadian effects on numerous mammalian species, and that given conservation of anatomy and function, the efficacy of light in this range in humans warrants further investigation. We also provide recommendations for the field of chronobiological research, including minimum requirements for the measurement and reporting of light, standardization of terminology (specifically as it pertains to “dim” light), and ideas for reconsidering old data and designing new studies.
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Affiliation(s)
- Thijs J Walbeek
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA, United States.,Oregon Institute of Occupational Health Sciences, Oregon Health and Science University, Portland, OR, United States
| | - Elizabeth M Harrison
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA, United States
| | - Michael R Gorman
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA, United States.,Department of Psychology, University of California, San Diego, San Diego, CA, United States
| | - Gena L Glickman
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA, United States.,Departments of Psychiatry and Neuroscience, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
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3
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Circadian disruption impairs fear extinction and memory of conditioned safety in mice. Behav Brain Res 2020; 393:112788. [DOI: 10.1016/j.bbr.2020.112788] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Revised: 06/21/2020] [Accepted: 06/22/2020] [Indexed: 02/06/2023]
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Walbeek TJ, Harrison EM, Soler RR, Gorman MR. Enhanced Circadian Entrainment in Mice and Its Utility under Human Shiftwork Schedules. Clocks Sleep 2019; 1:394-413. [PMID: 33089177 PMCID: PMC7445835 DOI: 10.3390/clockssleep1030032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Accepted: 08/20/2019] [Indexed: 12/21/2022] Open
Abstract
The circadian system is generally considered to be incapable of adjusting to rapid changes in sleep/work demands. In shiftworkers this leads to chronic circadian disruption and sleep loss, which together predict underperformance at work and negative health consequences. Two distinct experimental protocols have been proposed to increase circadian flexibility in rodents using dim light at night: rhythm bifurcation and T-cycle (i.e., day length) entrainment. Successful translation of such protocols to human shiftworkers could facilitate alignment of internal time with external demands. To assess entrainment flexibility following bifurcation and exposure to T-cycles, mice in Study 1 were repeatedly phase-shifted. Mice from experimental conditions rapidly phase-shifted their activity, while control mice showed expected transient misalignment. In Study 2 and 3, mice followed a several weeks-long intervention designed to model a modified DuPont or Continental shiftwork schedule, respectively. For both schedules, bifurcation and nocturnal dim lighting reduced circadian misalignment. Together, these studies demonstrate proof of concept that mammalian circadian systems can be rendered sufficiently flexible to adapt to multiple, rapidly changing shiftwork schedules. Flexible adaptation to exotic light-dark cycles likely relies on entrainment mechanisms that are distinct from traditional entrainment.
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Affiliation(s)
- Thijs J. Walbeek
- Department of Psychology, University of California San Diego, La Jolla, CA 92093, USA
- Center for Circadian Biology, University of California San Diego, La Jolla, CA 92093, USA
- Correspondence: (T.J.W.); (M.R.G.); Tel.: +1-858-822-2466 (M.R.G.)
| | - Elizabeth M. Harrison
- Department of Psychology, University of California San Diego, La Jolla, CA 92093, USA
- Center for Circadian Biology, University of California San Diego, La Jolla, CA 92093, USA
| | - Robert R. Soler
- Department of Psychology, University of California San Diego, La Jolla, CA 92093, USA
| | - Michael R. Gorman
- Department of Psychology, University of California San Diego, La Jolla, CA 92093, USA
- Center for Circadian Biology, University of California San Diego, La Jolla, CA 92093, USA
- Correspondence: (T.J.W.); (M.R.G.); Tel.: +1-858-822-2466 (M.R.G.)
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5
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Walbeek TJ, Joye DAM, Mishra I, Gorman MR. Physiological, behavioral and environmental factors influence bifurcated circadian entrainment in mice. Physiol Behav 2019; 210:112625. [PMID: 31325510 DOI: 10.1016/j.physbeh.2019.112625] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 07/16/2019] [Accepted: 07/17/2019] [Indexed: 01/05/2023]
Abstract
Under permissive conditions, mice and hamsters exposed to a polyphasic light regime consisting of two light and two dark phases every 24 h (Light:Dark:Light:Dark; LDLD) can adopt a bifurcated entrainment pattern with roughly equal amounts of running wheel activity in each of the two nights. This rhythm "bifurcation" has significant after-effects on increased circadian adaptability: Mice that have been bifurcated show accelerated rates of re-entrainment after a sudden phase shift and have a markedly expanded range of entrainment. Identifying environmental and physiological factors that facilitate or prevent rhythm bifurcation in LDLD conditions will contribute to an understanding of mechanisms underlying enhanced circadian plasticity. Here we investigate the effects of sex, age, light intensity, access to a running wheel, melatonin, and diet composition on bifurcation behaviors of mice (C57Bl/6 J) exposed to LDLD. Female mice and young mice (<20 weeks) express more symmetrically bifurcated activity compared to male mice and older mice (>30 weeks). Additionally and independently, higher photophase intensities (~500 lx) predict more symmetric entrainment than low levels of light (~50 lx). Without access to a functional running-wheel, mice do not adopt bimodal activity patterns and only transiently maintain them, suggesting that high levels of aerobic activity are necessary for rhythm bifurcation. Neither a lifetime exposure to melatonin administered in the drinking water nor a high fat diet affected bifurcation. Collectively, these results demonstrate that circadian plasticity can be strongly modulated by intrinsic and extrinsic factors. With enhanced mechanistic understanding of this modulation, it may be possible to render human clocks more adaptable and thereby ameliorate negative consequences associated with repeated jet-lag or shift-work.
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Affiliation(s)
- Thijs J Walbeek
- Department of Psychology, University of California San Diego, La Jolla, CA 92093, United States of America; Center for Circadian Biology, University of California San Diego, La Jolla, CA 92093, United States of America.
| | - Deborah A M Joye
- Department of Psychology, University of California San Diego, La Jolla, CA 92093, United States of America; Center for Circadian Biology, University of California San Diego, La Jolla, CA 92093, United States of America
| | - Ila Mishra
- Center for Circadian Biology, University of California San Diego, La Jolla, CA 92093, United States of America; Department of Zoology, University of Delhi, Delhi 110007, India
| | - Michael R Gorman
- Department of Psychology, University of California San Diego, La Jolla, CA 92093, United States of America; Center for Circadian Biology, University of California San Diego, La Jolla, CA 92093, United States of America
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Sun J, Joye DAM, Farkas AH, Gorman MR. Photoperiodic Requirements for Induction and Maintenance of Rhythm Bifurcation and Extraordinary Entrainment in Male Mice. Clocks Sleep 2019; 1:290-305. [PMID: 33089170 PMCID: PMC7445826 DOI: 10.3390/clockssleep1030025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 06/27/2019] [Indexed: 11/18/2022] Open
Abstract
Exposure of mice to a 24 h light:dark:light:dark (LDLD) cycle with dimly illuminated nights induces the circadian timing system to program two intervals of activity and two intervals of rest per 24 h cycle and subsequently allows entrainment to a variety of extraordinary light regimens including 30 h LDLD cycles. Little is known about critical lighting requirements to induce and maintain this non-standard entrainment pattern, termed “bifurcation,” and to enhance the range of apparent entrainment. The current study determined the necessary duration of the photophase for animals to bifurcate and assessed whether requirements for maintenance differed from those for induction. An objective index of bifurcated entrainment varied with length of the photophase over 4–10 h durations, with highest values at 8 h. To assess photic requirements for the maintenance of bifurcation, mice from each group were subsequently exposed to the LDLD cycle with 4 h photophases. While insufficient to induce bifurcation, this photoperiod maintained bifurcation in mice transferred from inductive LDLD cycles. Entrainment to 30 h LDLD cycles also varied with photoperiod duration. These studies characterize non-invasive tools that reveal latent flexibility in the circadian control of rest/activity cycles with important translational potential for addressing needs of human shift-workers.
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7
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Harrison EM, Yablonsky AM, Powell AL, Ancoli-Israel S, Glickman GL. Reported light in the sleep environment: enhancement of the sleep diary. Nat Sci Sleep 2019; 11:11-26. [PMID: 30988646 PMCID: PMC6438264 DOI: 10.2147/nss.s193902] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Light is the primary synchronizing cue for the circadian timing system, capable of exerting robust physiological effects, even with very dim and/or brief photic exposure. Mammals, including humans, are particularly susceptible to light at night. As such, measures of light in the sleeping environment are critical for evaluating sleep health. Sleep diaries provide inexpensive measures of sleep, but do not typically include light information. METHODS Four questions probing visual perception of light in the bedtime and waking environments were added to the Consensus Sleep Diary for Morning administration. As part of a lighting intervention study, 18 hospital Labor and Delivery Department personnel completed the sleep diary for 1 week in each of two experimental conditions while wearing Actiwatch devices equipped with photosensors. Diary responses were evaluated against photosensor values from the beginning and end of each rest interval (n=194 rest intervals), as well as against sleep measures, utilizing linear mixed models. RESULTS Responses to light questions were related to actual light measures at bedtime, controlling for shift type and experimental condition. In addition, subjective light information at bedtime and waking was related to both objective and subjective sleep parameters, with data generally indicating poorer sleep with light in the sleeping environment. CONCLUSION Questions addressing perception of light in the sleeping environment may provide a crude yet affordable metric of relative photic intensity. Further, as responses relate to sleep outcomes, subjective light information may yield valuable insights regarding mechanisms and outcomes of clinical significance in sleep and circadian research.
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Affiliation(s)
| | - Abigail M Yablonsky
- Clinical Investigations Department, Naval Medical Center San Diego, San Diego, CA, USA
| | - Alexandra L Powell
- Center for Circadian Biology, University of California, San Diego, CA, USA,
| | - Sonia Ancoli-Israel
- Center for Circadian Biology, University of California, San Diego, CA, USA,
- Department of Psychiatry, University of California, San Diego, CA, USA
| | - Gena L Glickman
- Center for Circadian Biology, University of California, San Diego, CA, USA,
- Department of Psychiatry, Uniformed Services University, Bethesda, MD, USA
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8
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Noguchi T, Harrison EM, Sun J, May D, Ng A, Welsh DK, Gorman MR. Circadian rhythm bifurcation induces flexible phase resetting by reducing circadian amplitude. Eur J Neurosci 2018; 51:2329-2342. [PMID: 30044021 DOI: 10.1111/ejn.14086] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 06/21/2018] [Accepted: 07/04/2018] [Indexed: 11/29/2022]
Abstract
Shift-work and jet-lag-related disorders are caused by the limited flexibility of the suprachiasmatic nucleus (SCN), a master circadian clock in the hypothalamus, to adjust to new light-dark (LD) cycles. Recent findings confirmed here establish that behavioral jet lag after simulated time-zone travel is virtually eliminated following bifurcated circadian entrainment under a novel and atypical 24-h light:dark:light:dark (LDLD) cycle. To investigate the mechanisms of this fast resetting, we examined the oscillatory stability of the SCN and peripheral tissues in LDLD-bifurcated mice employing the dissection procedure as a perturbing resetting stimulus. SCN, lung, liver, and adrenal tissue were extracted at times throughout the day from female and male PER2::Luciferase knock-in mice entrained to either LDLD or a normal LD cycle. Except for adrenals, the phase of the cultured explants was more strongly set by dissection under LDLD than under normal LD. Acute bioluminescence levels of SCN explants indicate that the rhythm amplitude of PER2 is reduced and phase is altered in LDLD. Real-time quantitative PCR suggests that amplitude and rhythmicity of canonical clock genes in the lung, liver, and kidney are also significantly reduced in LDLD in vivo. Furthermore, spatiotemporal patterns of PER2 peak time in cultured SCN were altered in LDLD. These results suggest that altered gene expression patterns in the SCN caused by bifurcation likely result in fast resetting of behavior and cultured explants, consistent with previously reported mathematical models. Thus, non-invasive, simple light manipulations can make circadian rhythms more adaptable to abrupt shifts in the environmental LD cycle.
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Affiliation(s)
- Takako Noguchi
- Center for Circadian Biology, UCSD, La Jolla, California
| | - Elizabeth M Harrison
- Center for Circadian Biology, UCSD, La Jolla, California.,Department of Psychology, UCSD, La Jolla, California
| | - Jonathan Sun
- Center for Circadian Biology, UCSD, La Jolla, California.,Department of Psychology, UCSD, La Jolla, California
| | - Deborah May
- Center for Circadian Biology, UCSD, La Jolla, California.,Department of Psychology, UCSD, La Jolla, California
| | - Alan Ng
- Center for Circadian Biology, UCSD, La Jolla, California.,Department of Biology, UCSD, La Jolla, California
| | - David K Welsh
- Center for Circadian Biology, UCSD, La Jolla, California.,Department of Psychiatry, UCSD, La Jolla, California.,Veterans Affairs San Diego Healthcare System, San Diego, California
| | - Michael R Gorman
- Center for Circadian Biology, UCSD, La Jolla, California.,Department of Psychology, UCSD, La Jolla, California
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9
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Walbeek TJ, Gorman MR. Simple Lighting Manipulations Facilitate Behavioral Entrainment of Mice to 18-h Days. J Biol Rhythms 2017; 32:309-322. [PMID: 28770653 DOI: 10.1177/0748730417718347] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In an invariantly rhythmic world, a robust and stable mammalian circadian clock is presumed to confer fitness advantages. In shift-work or after rapid transmeridian travel, however, a stable clock might be maladaptive and a more flexibly resettable clock may have advantages. The rate at which rodents can adjust to simulated time zone travel and the range of entrainment can be markedly increased through simple light manipulations, namely, by exposing animals to extremely dim light (<0.01 lux) at night or by bifurcating rhythms under 24-h light-dark-light-dark (LDLD) cycles. Here we investigated the separate effects of dim light and bifurcation on the ability of mice to entrain to 18-h days (LD 13:5; T18). Incorporating dim light at night, mice in Experiment 1 were exposed either to LD cycles with photophases that were progressively shortened from LD 19:5 to LD 13:5 or to bifurcating LDLD cycles with photophases that were lengthened from LDLD 7:5:7:5 to LDLD 13:5:13:5. In both cases, wheel-running rhythms were robustly synchronized to T18 and the phase of the free-running circadian rhythm was controlled by the timing of release into constant conditions. In Experiment 2, either dimly illuminated nights or a history of bifurcation without continuing dim light was sufficient to allow behavioral entrainment to T18 whereas previously unbifurcated mice under dark nights failed to entrain to T18. Additionally, concurrent measurement of body temperature rhythms in T24 LDLD revealed them to be bimodal. These studies suggest that the circadian system is markedly more flexible than conventionally thought and that this flexibility can be achieved in a noninvasive and nonpharmacological way. Facilitation of behavioral entrainment to extreme light-dark cycles may have translational potential for human shift-workers.
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Affiliation(s)
- Thijs J Walbeek
- Department of Psychology and Center for Circadian Biology, University of California San Diego, La Jolla, California
| | - Michael R Gorman
- Department of Psychology and Center for Circadian Biology, University of California San Diego, La Jolla, California
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Harrison EM, Carmack SA, Block CL, Sun J, Anagnostaras SG, Gorman MR. Circadian waveform bifurcation, but not phase-shifting, leaves cued fear memory intact. Physiol Behav 2017; 169:106-113. [DOI: 10.1016/j.physbeh.2016.11.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Revised: 10/26/2016] [Accepted: 11/21/2016] [Indexed: 11/25/2022]
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Harrison EM, Walbeek TJ, Sun J, Johnson J, Poonawala Q, Gorman MR. Extraordinary behavioral entrainment following circadian rhythm bifurcation in mice. Sci Rep 2016; 6:38479. [PMID: 27929128 PMCID: PMC5144065 DOI: 10.1038/srep38479] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 11/09/2016] [Indexed: 01/01/2023] Open
Abstract
The mammalian circadian timing system uses light to synchronize endogenously generated rhythms with the environmental day. Entrainment to schedules that deviate significantly from 24 h (T24) has been viewed as unlikely because the circadian pacemaker appears capable only of small, incremental responses to brief light exposures. Challenging this view, we demonstrate that simple manipulations of light alone induce extreme plasticity in the circadian system of mice. Firstly, exposure to dim nocturnal illumination (<0.1 lux), rather than completely dark nights, permits expression of an altered circadian waveform wherein mice in light/dark/light/dark (LDLD) cycles “bifurcate” their rhythms into two rest and activity intervals per 24 h. Secondly, this bifurcated state enables mice to adopt stable activity rhythms under 15 or 30 h days (LDLD T15/T30), well beyond conventional limits of entrainment. Continuation of dim light is unnecessary for T15/30 behavioral entrainment following bifurcation. Finally, neither dim light alone nor a shortened night is sufficient for the extraordinary entrainment observed under bifurcation. Thus, we demonstrate in a non-pharmacological, non-genetic manipulation that the circadian system is far more flexible than previously thought. These findings challenge the current conception of entrainment and its underlying principles, and reveal new potential targets for circadian interventions.
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Affiliation(s)
- Elizabeth M Harrison
- Center for Circadian Biology, University of San Diego, California, 9500 Gilman Dr. La Jolla, CA 92093, USA.,Department of Psychology, University of California, San Diego, 9500 Gilman Dr. La Jolla, CA 92093, USA
| | - Thijs J Walbeek
- Center for Circadian Biology, University of San Diego, California, 9500 Gilman Dr. La Jolla, CA 92093, USA.,Department of Psychology, University of California, San Diego, 9500 Gilman Dr. La Jolla, CA 92093, USA
| | - Jonathan Sun
- Center for Circadian Biology, University of San Diego, California, 9500 Gilman Dr. La Jolla, CA 92093, USA.,Department of Psychology, University of California, San Diego, 9500 Gilman Dr. La Jolla, CA 92093, USA
| | - Jeremy Johnson
- Center for Circadian Biology, University of San Diego, California, 9500 Gilman Dr. La Jolla, CA 92093, USA.,Department of Psychology, University of California, San Diego, 9500 Gilman Dr. La Jolla, CA 92093, USA
| | - Qays Poonawala
- Center for Circadian Biology, University of San Diego, California, 9500 Gilman Dr. La Jolla, CA 92093, USA.,Department of Psychology, University of California, San Diego, 9500 Gilman Dr. La Jolla, CA 92093, USA
| | - Michael R Gorman
- Center for Circadian Biology, University of San Diego, California, 9500 Gilman Dr. La Jolla, CA 92093, USA.,Department of Psychology, University of California, San Diego, 9500 Gilman Dr. La Jolla, CA 92093, USA
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Wang X, Wang L, Xu Y, Yu Q, Li L, Guo Y. Intranasal administration of Exendin-4 antagonizes Aβ31-35-induced disruption of circadian rhythm and impairment of learning and memory. Aging Clin Exp Res 2016; 28:1259-1266. [PMID: 26920423 DOI: 10.1007/s40520-016-0548-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 02/09/2016] [Indexed: 11/27/2022]
Abstract
BACKGROUND The deposition of β-amyloid protein (Aβ) is one of the pathological characteristics of Alzheimer's disease (AD) and can disrupt circadian rhythm and impair learning and memory. Exendin-4, a therapeutic drug for type II diabetes mellitus (T2DM), exerts neuroprotective effects from the toxicity of Aβ. However, it is not clear whether Exendin-4 protects against Aβ-induced disruption of circadian rhythm. The neuroprotective effects of Exendin-4 have been studied using injection of Exendin-4 into the lateral ventricle and abdomen. However, these procedures are not suitable for clinical application. METHODS First, male C57BL/6 mice received triple distilled water or Exendin-4 (0.1 nmol, 0.5 nmol) by intranasal administration. Exendin-4 levels were measured in the hippocampal samples using an ELISA Kit. Then, the study examined whether intranasal or hippocampal administration of Exendin-4 antagonized Aβ-induced disruption of circadian rhythm as well as impairment of learning and memory using the wheel-running activity assay and the Morris water maze test. RESULTS The study showed that intranasally administered Exendin-4 passed through the blood-brain barrier. Aβ31-35 given by intrahippocampal injection disrupted circadian rhythm and impaired learning and memory in C57BL/6 mice, and Exendin-4 given by nasal cavity or hippocampal administration ameliorated Aβ31-35-induced circadian rhythm disturbance of locomotor activity and impairment of learning and memory. CONCLUSIONS These findings provide pivotal experimental support for further study of the neuroprotective effects and clinical application of Exendin-4.
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Affiliation(s)
- Xiaohui Wang
- Department of Pathology, Shanxi Medical University, Taiyuan, 030001, China.
| | - Li Wang
- Department of Pathology, Shanxi Medical University, Taiyuan, 030001, China
| | - Yunyun Xu
- Department of Pathology, Shanxi Medical University, Taiyuan, 030001, China
| | - Qianqian Yu
- Department of Pathology, Shanxi Medical University, Taiyuan, 030001, China
| | - Lin Li
- Key Laboratory of Cellular Physiology, Ministry of Education, Shanxi Medical University, Taiyuan, 030001, China
| | - Yanlin Guo
- Department of Pathology, Shanxi Medical University, Taiyuan, 030001, China
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