SCN Flashcards

1
Q

Evans (2016)

A

SCN = master clock. Self-sustained rhythms generated by 24h transcriptional-translational feedback loop (clock genes - molecular level). Coordinate rhythms in physiology and behaviour. Synced at tissue level via intercellular signalling (VIP).

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2
Q

Antle (2009)

A

Only some SCN endogenously rhythmic - intercellular signalling with neuropeptides e.g. NPY, also GABA. Possible pharmacological targets for circadian / sleep dysfunction?

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3
Q

Herzog 1997

A

SCN cells still generate rhythms when isolated

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4
Q

Prosser 2007

A

PK2 important signalling factor: syncs core SCN cells to shell. Peaks in day and suppresses locomotor activity in mice

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5
Q

SCN outputs

A

Other hypothalamic areas e.g. aVPN (melatonin release from pineal, CRH release), subventricular zone, DM nucleus, medial preoptic nucleus (GnRH)

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6
Q

DeCoursey 1989

A

SCN ablation and transplant of foetal tissue

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7
Q

DeCoursey 2000

A

Chipmunks

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8
Q

Lucas 2001

A

Blind people still entrain due to melanopsin RGCs

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9
Q

Hattar 2002

A

melanopsin tau:lacZ mouse and retrograde staining from SCN - down RHT to retina (1/100 RGCs)

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10
Q

Lucas 2003

A

Melanopsin RGCs intrinsically photoreceptive, emit APs in vitro. But cells from melanopsin K/O mice don’t show this

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11
Q

Melyan 2005

A

Put melanopsin into non-photoreceptive cell = becomes photoreceptive

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12
Q

Cholera toxin labelling

A

Stain RHT input to SCN: see tracts synapse in ventral pattern

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13
Q

Electromicrographs

A

Postsynaptic densities (RHT synapses) are Gray type I excitatory cells

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14
Q

PACAP immunostaining

A

Ventral pattern of PACAP staining in SCN: closely matches that of RHT innervation

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15
Q

Khalsa 2003

A

Similar pattern of PRC seen in humans e.g. light early in night = phase delay

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16
Q

van del pol 1998

A

Brief pulses (rather than continuous) of light = integrate and can cause even larger phase shifts

17
Q

Piggins and Guilding 2011

A

Photic and non-photic stimuli = differential PRCs

18
Q

Marston 2008

A

Rodents and arousal-promoting stimuli e.g. dark pulse late in subjective day = phase advance. 6h dark promotes arousal = less cFos expressed in SCN, higher activity in orexin neurons

19
Q

Harmar 2002

A

VPAC2R K/O mice = arrythmic in constant dark, no sync of SCN cells. Amp and synchrony of SCN cells impaired - need VIP signalling to synchronise

20
Q

Hughes 2015

A

VIP K/O mice in constant light = improved behavioural rhythms so shows light is crucial

21
Q

Yamaguchi 2013

A

AVPR K/O mice = resistant to jet lag. Entrain/phase shift much more rapidly, behavioural and molecular (clock gene expression)

22
Q

Mieda 2015

A

Also resistant to jet lag if no BMAL in AVP neurons. AVP tries to keep intact clock by resisting large changes in rhythm

23
Q

Piggins and Guilding 2011

A

Action of NTs e.g. Glu and PACAP activate VIP receptors in SCN to impact clock gene expression and set/reset phase

24
Q

Davis 2001

A

Higher breast cancer rates in night shift workers (constantly phase shifting / clock out of sync). Circadian dysfunction can lead to disease

25
van Someren 1997
BLT in care homes increases amp of circadian rhythms / improved entrainment (also helps with cognitive problems)
26
Lewy
Phase delay hypothesis for SAD
27
Murray 2003
Association between lowered/depressed mood in winter and winter phase delay
28
Mistlberger 2005
Opponent-process model. Lesion SCN = homeostatic only, short bouts of sleep/wake. Ignore sleep homeostat e.g. sleep deprivation = more tired in first night than third day Forced desynchrony - 28h day. Homeostasis always kept same but measured temp as output of circ clock = 24.3h, freerunning
29
VLPO
Light info travels down RHT to VLPO, forms excitatory synapses (can be seen with melanopsin tau:lacZ staining). VLPO is sleep-promoting (GABAergic neurons that switch off ARAS) so in mice = active during day (higher cFos expression). Lesion VLPO = disrupted sleep.
30
Roenneberg 2009
Chronotype: preferred phase of sleep/wake. Males later, changes with age etc. Social schedule interferes considerably with sleep/activity times so should try and change work/school schedules to suit chronotype! Social jet lag = wake up too early on weekdays, sleep deprived. Worse in young adults. Circadian clock controls sleep but according to solar cycle not social schedule!
31
LeGates 2014
Irregular light linked with depression.