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Article: Neural basis and biological function of masking by light in mammals: suppression of melatonin and locomotor activity.

Redlin, U

2003 Volume 18, Issue 5, Page(s) 737–758

Abstract: Light influences mammalian circadian rhythms in two different ways: (1) It entrains endogenous oscillators (clocks), which regulate physiology and behavior; and (2) it affects directly and often immediately physiology and behavior (these effects are also ...

Abstract	Light influences mammalian circadian rhythms in two different ways: (1) It entrains endogenous oscillators (clocks), which regulate physiology and behavior; and (2) it affects directly and often immediately physiology and behavior (these effects are also referred to as masking). Masking effects of light on pineal melatonin, locomotor activity, and the sleep-wake cycle in mammals and man are reviewed. They seem to represent a universal response in this group. The review reveals that the mechanism of photic inhibition of melatonin is fairly well understood, whereas only little is known about the influence of light on other circadian rhythm outputs, such as locomotor activity.
MeSH term(s)	Animals ; Chronobiology Phenomena ; Circadian Rhythm/physiology ; Circadian Rhythm/radiation effects ; Geniculate Bodies/physiology ; Geniculate Bodies/radiation effects ; Humans ; Light ; Melatonin/metabolism ; Motor Activity/physiology ; Motor Activity/radiation effects ; Nervous System Physiological Phenomena ; Photoreceptor Cells, Vertebrate/physiology ; Photoreceptor Cells, Vertebrate/radiation effects ; Pineal Gland/metabolism ; Preoptic Area/physiology ; Preoptic Area/radiation effects ; Sleep/physiology ; Sleep/radiation effects ; Suprachiasmatic Nucleus/physiology ; Visual Cortex/physiology ; Visual Cortex/radiation effects
Chemical Substances	Melatonin (JL5DK93RCL)
Language	English
Publishing date	2003-03-07
Publishing country	England
Document type	Journal Article ; Review
ZDB-ID	998996-1
ISSN	1525-6073 ; 0742-0528
ISSN (online)	1525-6073
ISSN	0742-0528
DOI	10.1081/cbi-100107511
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Article: Masking by light in hamsters with SCN lesions.

Redlin, U / Mrosovsky, N

Journal of comparative physiology. A, Sensory, neural, and behavioral physiology

1999 Volume 184, Issue 4, Page(s) 439–448

Abstract: Inhibition of wheel running by light (masking) was investigated in Syrian hamsters with suprachiasmatic nucleus or sham lesions. Approximately 90% of the wheel revolutions made by hamsters with complete suprachiasmatic nucleus lesions, as judged by ... ...

Abstract	Inhibition of wheel running by light (masking) was investigated in Syrian hamsters with suprachiasmatic nucleus or sham lesions. Approximately 90% of the wheel revolutions made by hamsters with complete suprachiasmatic nucleus lesions, as judged by histology and power spectrum analysis of their wheel running, occurred during the dark phases of an ultradian light-dark cycle (3.5 h light, 3.5 h dark). This was demonstrated for two illumination levels (380 lx and 6 lx). Similar results were obtained with sham-operated animals. In further tests, the hamsters with lesions also retained a strong preference for the dark side of a box divided into dark and light sides. These results demonstrate that the suprachiasmatic nucleus is not necessary for masking by light or the preference for a dark over a light compartment. Evidently the direct effects of light can substitute for the endogenous control by the suprachiasmatic nucleus to maintain appropriate behaviour in time and space.
MeSH term(s)	Activity Cycles/physiology ; Animals ; Circadian Rhythm/physiology ; Cricetinae ; Male ; Mesocricetus ; Motor Activity/physiology ; Photic Stimulation ; Suprachiasmatic Nucleus/physiology
Language	English
Publishing date	1999-04
Publishing country	Germany
Document type	Journal Article ; Research Support, Non-U.S. Gov't
DOI	10.1007/s003590050343
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Article: Masking of locomotor activity in hamsters.

Redlin, U / Mrosovsky, N

Journal of comparative physiology. A, Sensory, neural, and behavioral physiology

1999 Volume 184, Issue 4, Page(s) 429–437

Abstract: The inhibition of locomotion by light (masking) was investigated in Syrian hamsters. When 1-h pulses of light were presented in the early night, activity was strongly suppressed by irradiances of about 1 lx or greater. Ultradian light-dark cycles were ... ...

Abstract	The inhibition of locomotion by light (masking) was investigated in Syrian hamsters. When 1-h pulses of light were presented in the early night, activity was strongly suppressed by irradiances of about 1 lx or greater. Ultradian light-dark cycles were used as another way to study masking. Hamsters were unable to entrain to 3.5:3.5-h light-dark cycles, thus permitting the masking and the entraining effects of light to be distinguished. Light had greater suppressive effects on activity in home cages than on activity in novel running wheels. Moreover, in home cages activity remained very low for about 30 min after lights were turned off. Post-pulse suppression of activity was not simply a consequence of reduced running, as shown by experiments in which running was temporarily prevented by locking the wheels. A phase response curve for masking was obtained by placing hamsters in novel wheels for 3-h periods at various times throughout their circadian cycles, and then superimposing a 30-min light pulse. The suppressive effect of light was maximal around the onset of activity, which normally coincides with dusk in hamsters. This may have adaptive value in limiting foraging to the hours of darkness.
MeSH term(s)	Activity Cycles/physiology ; Animals ; Circadian Rhythm/physiology ; Cricetinae ; Male ; Mesocricetus ; Motor Activity/physiology ; Photic Stimulation
Language	English
Publishing date	1999-04
Publishing country	Germany
Document type	Journal Article ; Research Support, Non-U.S. Gov't
DOI	10.1007/s003590050342
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Article: Effects of pinealectomy on SCN electrical firing rhythm in Djungarian hamsters.

Redlin, U / Lynch, G R

Neuroscience letters

1997 Volume 236, Issue 2, Page(s) 67–70

Abstract: Djungarian hamsters (Phodopus sungorus) from a long day photoperiod (16:8 h light-dark cycle) were either pinealectomized (PINX; n = 7) or sham-pinealectomized (SHAM; n = 6). One week after surgery coronal brain slices (500 microm), containing the ... ...

Abstract	Djungarian hamsters (Phodopus sungorus) from a long day photoperiod (16:8 h light-dark cycle) were either pinealectomized (PINX; n = 7) or sham-pinealectomized (SHAM; n = 6). One week after surgery coronal brain slices (500 microm), containing the suprachiasmatic nucleus (SCN), were prepared. The firing-rate rhythm of SCN neurons was recorded over at least a 22 h period. The amplitude of the firing rhythm for SHAM slices (3.42 +/- 0.26 Hz) was not significantly different from PINX slices (3.45 +/- 0.29 Hz). Maxima and minima of the firing rhythms also could not be distinguished statistically between PINX and SHAM groups. However, two-way ANOVA of 2 h firing-rate averages indicated a statistically significant effect of pinealectomy on the firing rhythm (P < 0.01). The results show that pinealectomy one week prior to brain slice preparation only had a minor effect on the in vitro neuronal firing rhythm in the SCN. In this study, SCN firing-rate rhythm in the Djungarian hamster is largely independent of endogenous melatonin secretion.
MeSH term(s)	Analysis of Variance ; Animals ; Cricetinae ; Electrophysiology ; In Vitro Techniques ; Pineal Gland/physiology ; Pineal Gland/surgery ; Suprachiasmatic Nucleus/physiology
Language	English
Publishing date	1997-10-31
Publishing country	Ireland
Document type	Journal Article ; Research Support, U.S. Gov't, P.H.S.
ZDB-ID	194929-9
ISSN	1872-7972 ; 0304-3940
ISSN (online)	1872-7972
ISSN	0304-3940
DOI	10.1016/s0304-3940(97)00754-4
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Article: Exercise and human circadian rhythms: what we know and what we need to know.

Redlin, U / Mrosovsky, N

Chronobiology international

1997 Volume 14, Issue 2, Page(s) 221–229

Abstract: A synopsis of the effects of exercise on the circadian system in nocturnal rodents is followed by a review of the few studies investigating the influence of exercise on the human circadian system. It is premature to make specific recommendations about ... ...

Abstract	A synopsis of the effects of exercise on the circadian system in nocturnal rodents is followed by a review of the few studies investigating the influence of exercise on the human circadian system. It is premature to make specific recommendations about using exercise to promote synchronization in people because of the lack of information on the best times of exercise, the amounts required, and interactions between nonphotic and photic zeitgebers.
MeSH term(s)	Animals ; Circadian Rhythm ; Darkness ; Exercise ; Humans ; Light ; Melatonin/blood ; Melatonin/metabolism ; Motor Activity ; Rodentia
Chemical Substances	Melatonin (JL5DK93RCL)
Language	English
Publishing date	1997-03
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't ; Review
ZDB-ID	998996-1
ISSN	1525-6073 ; 0742-0528
ISSN (online)	1525-6073
ISSN	0742-0528
DOI	10.3109/07420529709001157
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Article: Masking in waved-2 mice: EGF receptor control of locomotion questioned.

Mrosovsky, N / Redlin, U / Roberts, R B / Threadgill, D W

Chronobiology international

2005 Volume 22, Issue 6, Page(s) 963–974

Abstract: It has been suggested that epidermal growth factors (EGF) are responsible for the inhibition of locomotion by light (i.e., masking) in nocturnal rodents (Kramer et al., 2001). The poor masking response of waved-2 (Egfr(wa2)) mutant mice, with reduced EGF ...

Abstract	It has been suggested that epidermal growth factors (EGF) are responsible for the inhibition of locomotion by light (i.e., masking) in nocturnal rodents (Kramer et al., 2001). The poor masking response of waved-2 (Egfr(wa2)) mutant mice, with reduced EGF receptor activity, was adduced in support of this idea. In the present work, we studied the responses to light over a large range in illumination levels, in a variety of tests, with pulses of light and with ultradian light-dark cycles in Egfr(wa2) mutant mice. No evidence suggested that normal functioning of epidermal growth factor receptors was required, or even involved, in masking.
MeSH term(s)	Animals ; Circadian Rhythm/genetics ; DNA Primers ; Lighting ; Mice ; Mice, Mutant Strains ; Motor Activity/physiology ; Polymerase Chain Reaction ; Receptor, Epidermal Growth Factor/genetics
Chemical Substances	DNA Primers ; Receptor, Epidermal Growth Factor (EC 2.7.10.1)
Language	English
Publishing date	2005
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	998996-1
ISSN	1525-6073 ; 0742-0528
ISSN (online)	1525-6073
ISSN	0742-0528
DOI	10.1080/07420520500395086
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Article: Nocturnal activity in a diurnal rodent (Arvicanthis niloticus): the importance of masking.

Redlin, Uwe / Mrosovsky, N

Journal of biological rhythms

2004 Volume 19, Issue 1, Page(s) 58–67

Abstract: It is known that day-active Nile grass rats, Arvicanthis niloticus, increase the amount of activity in the night relative to that in the day when provided with running wheels. This was confirmed in the present study. Animals without a wheel displayed 69 ... ...

Abstract	It is known that day-active Nile grass rats, Arvicanthis niloticus, increase the amount of activity in the night relative to that in the day when provided with running wheels. This was confirmed in the present study. Animals without a wheel displayed 69.0% of their general activity in the L phase of a 12:12 h light-dark cycle; animals provided with wheels had only 48.6% of their wheel revolutions in the light. The contribution of direct (masking) responses to light to the increased nocturnality of animals with wheels was examined in two experiments. In experiment 1, masking was tested by exposing the animals to repeated cycles of 30 min of entraining light and 30 min of a different, usually dimmer light, during the L phase of a 12:12 h light-dark cycle. For animals with wheels, there was more running during the 30-min pulses of dim light or darkness than during the 30-min periods of entraining light. In contrast, for animals without wheels, there was more general activity during the 30-min periods of entraining light than during the 30-min pulses of dim light or darkness. In experiment 2, the animals were first exposed to a 12:12 h light-dark cycle and then put on a 1:10:1:12 h LDLD skeleton photoperiod. Animals with wheels increased their running during the subjective day of the skeleton photoperiod compared to that in the actual day of the 12:12 h light-dark cycle. Animals without wheels showed similar levels of general activity during the subjective day of the skeleton photoperiod and the actual day of the 12:12 h cycle. These experiments demonstrate that when Nile rats have running wheels, their increased nocturnal activity is associated with an increased suppression of locomotion in direct response to light. It is possible that changes in masking responses to light may be an essential and integral component of switching between diurnal and nocturnal activity profiles.
MeSH term(s)	Animals ; Circadian Rhythm/physiology ; Light ; Male ; Motor Activity/physiology ; Perceptual Masking ; Photoperiod ; Rats
Language	English
Publishing date	2004-02
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	896387-3
ISSN	1552-4531 ; 0748-7304
ISSN (online)	1552-4531
ISSN	0748-7304
DOI	10.1177/0748730403260371
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Article: Enhanced masking response to light in hamsters with IGL lesions.

Redlin, U / Vrang, N / Mrosovsky, N

Journal of comparative physiology. A, Sensory, neural, and behavioral physiology

1999 Volume 184, Issue 4, Page(s) 449–456

Abstract: Syrian hamsters with intergeniculate leaflet or sham lesions were given tests with a series of light pulses of gradually decreasing intensities. The light pulses were given early in the night, at zeitgeber time 14-15. The amount of wheel running during ... ...

Abstract	Syrian hamsters with intergeniculate leaflet or sham lesions were given tests with a series of light pulses of gradually decreasing intensities. The light pulses were given early in the night, at zeitgeber time 14-15. The amount of wheel running during the pulses was compared to that in the same hour on a night with no light pulses. Hamsters with intergeniculate leaflet lesions showed a significantly greater suppression of their wheel running in response to light than the sham-lesioned animals. The lesioned animals also had larger negative phase angles of entrainment to the 14:10-h light-dark cycle than sham-operated controls. However, phase shifting in response to light pulses at either zeitgeber time 14 or 18 was not significantly altered by the lesions. Preferences for spending more time in a dark than a light area were not abolished by the lesions. It is concluded that the intergeniculate leaflet in the Syrian hamster cannot be of paramount importance for masking of locomotor activity by light but may play a modulating role.
MeSH term(s)	Activity Cycles/physiology ; Animals ; Circadian Rhythm/physiology ; Cricetinae ; Darkness ; Geniculate Bodies/physiology ; Immunohistochemistry ; Light ; Male ; Mesocricetus ; Motor Activity/physiology ; Photic Stimulation
Language	English
Publishing date	1999-04
Publishing country	Germany
Document type	Journal Article ; Research Support, Non-U.S. Gov't
DOI	10.1007/s003590050344
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Article: Lengthening of circadian period in hamsters by novelty-induced wheel running.

Weisgerber, D / Redlin, U / Mrosovsky, N

Physiology & behavior

1997 Volume 62, Issue 4, Page(s) 759–765

Abstract: Phase shifts resulting from nonphotic events can be accompanied by sizable changes in the free-running period. This study examined the relationship between tau changes and phase shifts produced by confining Syrian hamsters to a novel running wheel in the ...

Abstract	Phase shifts resulting from nonphotic events can be accompanied by sizable changes in the free-running period. This study examined the relationship between tau changes and phase shifts produced by confining Syrian hamsters to a novel running wheel in the mid-subjective day. Both phase shifting and tau lengthening were higher in animals that made a high number of wheel turns in the 3 h in the novel wheel. Hamsters that ran little during the activity pulse, and did not subsequently exhibit either phase shifts or tau lengthening, had low baseline activity and long taus before the pulse. However, long taus did not preclude hamsters from running in a novel wheel and subsequently phase shifting. This was demonstrated by finding the phase shifts after activity pulses in animals whose tau had already been lengthened by previous activity pulses in novel wheels. The possibility is discussed that feedback from locomotor activity influences the period of the clock in hamsters, but it is concluded that, in addition, there must be other mechanisms accounting for the relationships between activity and tau.
MeSH term(s)	Animals ; Circadian Rhythm/physiology ; Cricetinae ; Feedback/physiology ; Locomotion/physiology ; Male
Language	English
Publishing date	1997-10
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	3907-x
ISSN	1873-507X ; 0031-9384
ISSN (online)	1873-507X
ISSN	0031-9384
DOI	10.1016/s0031-9384(97)00192-3
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Article: The circadian Clock mutant mouse: impaired masking response to light.

Redlin, Uwe / Hattar, Samer / Mrosovsky, N

Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology

2005 Volume 191, Issue 1, Page(s) 51–59

Abstract: Synchronization of an internal clock (entrainment) and a direct response to light (masking) are complementary ways of restricting activity of an animal to day or night. The protein CLOCK has an important role in the oscillatory mechanism of mammalian ... ...

Abstract	Synchronization of an internal clock (entrainment) and a direct response to light (masking) are complementary ways of restricting activity of an animal to day or night. The protein CLOCK has an important role in the oscillatory mechanism of mammalian pacemakers. Our data show that it is also involved in masking responses. Mice with the Clock/Clock mutation reduced their wheel running less than wildtypes when given 1-h light pulses of light (2-1,600 lx) in the night. With dimmer lights (<2 lx), there were no significant differences between mutant and wildtype mice. Impaired masking responses to light in Clock/Clock mice were confirmed in tests with ultradian light-dark cycles (3.5:3.5 h and 1:1 h). Tests with pulses of light longer than 1 h revealed that, although the mutants responded more slowly to light, they sustained the suppression of activity over the course of the 3-h tests better than wildtypes.
MeSH term(s)	Activity Cycles/physiology ; Activity Cycles/radiation effects ; Animals ; CLOCK Proteins ; Circadian Rhythm/physiology ; Circadian Rhythm/radiation effects ; Light ; Light Signal Transduction/genetics ; Light Signal Transduction/physiology ; Light Signal Transduction/radiation effects ; Mice ; Mice, Inbred C57BL ; Mice, Mutant Strains ; Motor Activity/physiology ; Motor Activity/radiation effects ; Perceptual Masking/physiology ; Trans-Activators/genetics ; Trans-Activators/physiology
Chemical Substances	Trans-Activators ; CLOCK Proteins (EC 2.3.1.48) ; Clock protein, mouse (EC 2.3.1.48)
Language	English
Publishing date	2005-01
Publishing country	Germany
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	120907-3
ISSN	1432-1351 ; 0340-7594 ; 0302-9824 ; 0373-0859
ISSN (online)	1432-1351
ISSN	0340-7594 ; 0302-9824 ; 0373-0859
DOI	10.1007/s00359-004-0570-z
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