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The effect of bright light on blood pressure and heart rate in essential hypertension


This conference paper represents the data of a 24 hour radio-telemetric monitoring of blood pressure and heart rate in spontaneously hypertensive (SHR) and normotensive (Wistar-Kyoto) rats exposed to 1 hour action of 10 000 lux LED bright light (model of bright light therapy used for treatment of seasonal affective disorders (SAD), seasonal and non-seasonal depression, disorders of sleep and so on).
New York
New Delhi
Kuala Lumpur
Society for Light Treatment and
Biological Rhythms, 30th Annual
Meeting, Groningen (The Netherlands),
June 21–24, 2018
Guest Editors
Mirjam Münch, Berlin
Anna Wirz-Justice, Basel
Abstracts Neuropsychobiology 2017;76:1–46
DOI: 10.1159/000489584
Prolonged Photoperiod Induces Changes in
Sleep: The Impact of Blue-Enriched Light
Louise H. Bjerrum1, Torhild T. Pedersen1, Jelena Mrdalj1,
Jonathan P. Wisor2, Andrea R. Marti1, Michael Rempe2,3,
Tone E.G. Henriksen1,4, Janne Grønli1
1University of Bergen, Bergen, Norway; 2Washington State
University, Spokane, WA, USA; 3Whitworth University,
Spokane, USA; 4Valen Hospital, Helse Fonna, Norway
Objectives: Light exerts a direct effect on slow-wave sleep
(SWS) and electroencephalogram (EEG) slow-wave activity
(SWA; 0.5–4 Hz). It has been suggested that blue-enriched light
promotes alertness in both humans and rodents through signaling
via intrinsic photosensitive retinal ganglion cells (ipRGCs). Here
we use a model of prolonged photoperiod (20 h light, 4 h dark; 20:4
LD) of two different light spectra (white and blue-enriched) to
characterize the effects on sleep in rats.
Methods: Rats (n = 6/group) were housed in 12:12 LD cycle
for 5 days, followed by 7 days of exposure to prolonged photope-
riod 20:4 LD in either white or blue-enriched light, and 7 days re-
covery in 12:12 LD. Sleep (EEG and electromyogram) was re-
corded continuously by means of telemetry. We report data (% ±
SEM change from 24 h baseline) and statistical analyses on total
sleep time (TST), time in SWS, and SWA from day 7 of exposure
to prolonged photoperiod (E7), and recovery day 1–7 (R1–R7).
Results: At E7, only white light increased TST (white: 8.9 ±
3.6%, p = 0.004 vs. blue: 3.6 ± 1.5%, p = 0.155) and time in SWS
(white: 8.9 ± 3.7%, p = 0.014 vs. blue: 4.1 ± 1.7%, p = 0.193). SWA
in SWS was not significantly changed at E7 compared to baseline.
During recovery in the 12:12 LD condition, TST was increased at
R2 (prolonged white: 8.3 ± 3.4%, p = 0.023), R3 (prolonged blue:
8.3 ± 3.4%, p = 0.030) and R4 (prolonged blue: 7.5 ± 3.1%, p =
0.042) compared to baseline. Time in SWS and SWA in SWS
showed no significant differences at R1-R7 compared to baseline.
Conclusions: Prolonged photoperiod has short and long-
term effects on sleep in the rat, and the effects are dependent upon
light spectra. Prolonged exposure to white light increased total
sleep time and time spent in slow-wave sleep, whereas prolonged
exposure to blue-enriched light increased total sleep time in recov-
ery only.
Funding/Disclosures: The work was funded by Helse Vest
(ID HV911 893) and the Faculty of Psychology, University of Ber-
gen (Småforsk, ID 173200-270452).
The Effect of Bright Light on Blood Pressure
and Heart Rate in Essential Hypertension
Mikhail L. Blagonravov, Anna A. Bryk,
Evgenia V. Medvedeva, Vyacheslav A. Goryachev,
Sergey M. Chibisov, Sergey P. Syatkin, Madina M. Azova,
Tatyana Y. Zotova
Peoples’ Friendship University of Russia (RUDN University),
Moscow, Russia
Objectives: Bright light therapy (BLT) showed positive re-
sults with respect to seasonal affective disorders, non-seasonal de-
pression, sleep disorders and so on. Meanwhile, there is still little
data concerning the effects of light therapy on functional activity
of the cardiovascular system and particularly in case of hyperten-
sion. We therefore studied the features of daytime and nighttime
blood pressure (BP) and heart rate (HR) in genetically hyperten-
sive and normotensive rats under the action of bright light (BL).
Methods: We performed our experiments on 32–34 weeks
old male rats of SHR (hypertensive, n = 5) and Wistar-Kyoto (nor-
motensive, n = 5) strains. Animals were kept in individual cages
under 12:12 h light-dark schedule with light on at 7.00 am and off
at 7.00 pm, daytime ~ 300 lux white light at eye level and night-
time absolute darkness. To estimate the effect of BL the animals
were exposed to 1 hour action of ~ 10,000 lux white LED light
from 10.00 am to 11.00 am. Systolic and diastolic blood pressure
(SBP and DBP), heart rate (HR) were monitored continuously for
24 hours the day before (controls) and on the very day of BL ex-
posure. BP and HR monitoring was carried out with the use of
radio-telemetry system (DSI, USA) which consists of radio-trans-
mitter (sensor) DSI HD-S11 implanted in the animal body, receiv-
er, data exchange matrix and computer for storing data. BP was
monitored in the lumen of the abdominal aorta. Thanks to the use
of implantable sensors animals were totally freely moving the
whole duration of the experiment. The data was processed with
software Dataquest A.R.T. 4.33 (DSI, USA).
Results: It was found that SBP and DBP were significantly
higher in the SHR rats compared to the normotensive rats for the
whole 1 hour period of BL exposure in comparison with the same
time interval (from 10.00 to 11.00 am) of the previous day when
BL was not used. The average levels of daytime (10.00 am – 7.00
pm) SBP and DBP were significantly increased in the hypertensive
rats compared with the control rats which might indicate that the
effect of BL remains notable even after the end of its exposure. For
HR only a clearly defined tendency to an increase was seen. For
the nighttime period after the day of BL exposure all of the moni-
tored parameters of the hypertensive rats had the same values as in
the controls. In normotensive rats the action of BL induced no sig-
nificant changes in BP or HR.
Conclusions: Our data shows that BL induces an increase in
BP in hypertensive but not in normotensive rats both at the time of
BL exposure and after it. This should be taken into account when
using BLT in case of concomitant hypertension.
Funding/Disclosures: The publication was prepared with
the support of the “RUDN University Program 5-100”.
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