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17 Cards in this Set
- Front
- Back
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Aschoff's First Rule
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In diurnal animals, LL shortens tau, while DD lengthens it.
In nocturnal animals, LL lengthens tau, while DD shortens it. |
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Aschoff's Second Rule
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Under constant bright light (LL),
diurnal animals lengthen their period of activity, while nocturnal animals shorten their period of activity. |
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Aschoff's Third Rule
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In DD,
tau > 24h in diurnal animals tau < 24 h in nocturnal animals |
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Schwartz et al. (1987)
TTX canula into SCN |
TTX shut down neural output of SCN, clocks resumed free-running after TTX input stopped.
SCN is NECESSARY for circadian rhythms |
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Pickard & Turek (1982)
split lesions |
Lesioned one of the SCN, both, or neither in animals with split rhythms.
sham surgery, two taus. unilateral SCNx, one tau. bilateral SCNx, rhythms abolished. SCN is NECESSARY |
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Schwartz and Gainer (1977)
2DG slices |
Injected radio-labeled 2DG sugar, kill animals, take brain slices at different times in circadian cycle.
In both diurnal and nocturnal SCN used 2DG during subjective day. |
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Inouye & Kawamura (1979)
hypothalamic island |
separated neural connections of a conical section of the brain (including SCN) from the rest of the brain.
no rhythm outside island, rhythm inside. SCN is SUFFICIENT |
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LeSauter et al. (1996)
mutant transplant |
Transplanted SCNs from tau-mutant hamsters to non-mutant hamsters. Taus were similarly transplanted.
Location not important. SCN is SUFFICIENT |
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evidence for SCN necessary
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SCNx abolishes not one but many CRs
Reversible “lesion” with TTX mask expression of CRs but do not alter timekeeping of clock Isolation of SCN abolishes CR in MUA in rest of brain Unilateral SCNx abolishes splitting |
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evidence for SCN sufficient
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CR in 2-DG utilization in DD
Persistence of CR in multiple unit activity (MUA) inside hypothalamic islands Transplants of fetal SCN restore donor period Electrical stimulation of the SCN resets phase of CR in feeding activity Transplants do not, however, restore endocrine rhythms |
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Welsh et al. (1995)
SCN electrode tray |
Lay fetal SCN tissue on an electrode tray. Electrodes pierced some cells as they grew, allowed measurement of phase. cells out of phase with each other.
led to research showing nonclock cells dictate the phase of nearby clock cells. |
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SCN core
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retino-recipient
NON-oscillatory CalB+ |
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SCN shell
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not retino-recipient
oscillatory VP+ |
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GRP
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synchronizing chemical for SCN
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Silver et al.
ziplocs |
Put SCN transplant into diffusible tiny bags
Periodograms show that animals regain rhythmicity without having the possibility of any neurogenesis |
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Yamazaki et al. (2000)
glow rats |
Made rats that produce luciferase whenever they produce per1.
Rhythmicity dampened in periphery, has a lag in circadian oscillators in the body as compared to the SCN. |
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Guo et al. (2005)
parabiosis |
Sewed two animals together. Showed that having one unlesioned animal with one SCNx animal restored some rhythms, but not others.
Does not establish neural connections, but makes strong argument. |
