Extra-SCN brain oscillators Flashcards
What was observed when measuring locomotor activity in the common vole?
What does this mean?
How was this cycle observed in newborns?
Ultradian feeding behavoiur
Voles eat grass which is hard to do and takes time due to their size, cannot sustain 12 hour fasting period
Voles will come out to eat at the same time to avoid predation
BUT Voles with lesioned SCN / subjected to food deprivation maintained rhythmicity
Must be driven by an oscillator not in the SCN
Newborns displayed this ultradian rhythmicity as soon as they were born
Evovled from SCN to ‘smooth out’ slight differences in cycles, much more labile than SCN
Describe the rhythms observed in the Svalbard reindeer at 78 degrees N
A circadian pattern was vaguely visible during the times of the month when an LD period was present, but this pattern vanishes as soon as constant light/dark is established (often when so far north)
No light entrainment means any slight differences in FRP would lead to total herd desynchrony
However, another, ultradian clock is going on to synchronize
What was ovserved when knocking out Bmal1, Cry1/2, and Clk individually in mice?
Loss of circadian rhythm during DD, but some ultradian rhythmicity (nothing definitive proven)
Describe the presence and role of monoamines in the ascending arousal system
Which is most important?
DA, His, 5-HT and NA are all found in the ascending arousal system
Pertubation here leads to psychopathology
Removing any of these leads to mild phenotypes EXCEPT for Dopamine, which the animal cannot live without
What is the role of DAT and what happens when it is knocked out in mice?
Dopamine transporter, shuttles DA back into presynaptic neuron after it is released
DAT KO mice have increased levels of DA all the time
DATKO mice don’t eat and die off easily
Seemingly short FRP, but possible second ultradian clock?
What causes a two-phase oscillation in hamsters?
What happens to the acrogram of a rat exposed to a 22-hour day? What causes this?
What mutation erases this phenomena?
Constant light exposure causes two SCN to become antiphasic
Two locomotor activity rhythms emerge
Due to desynchronization of ventrolateral SCN and dorsomedial SCN neurons
Both SCN are in phase, but the vental and dorsal regions are out of phase (recall ventral SCN receives light input, dorsal is in true FRP as it is not entrained by light)
Neither of these phenomena are observed in DAT KO mice (the SCN appears to be functioning normally)
What was observed when measuring running wheel activity in SCNx-DAT-/- mice in DD?
Removal of DAT removes ultradian oscillation (independent of SCN)
image: Slc6a3 is the gene encoding DAT
What increases extracellular dopamine in brains with healthy DATs?
(meth)amphetamine treatment and DAT disruption
What happens when measuring locomotor activity in Bmal1 -/- mice during DD, while receiving methamphetamine??
Methamphetamine lengthens ultradian locomotor period in a dose-dependent manner
How are dopamine and activity related in Bmal1-/- mice?
Activity is followed closely by dopamine
image, dopamine is the dialysate used in this assay
Describe the Dopaminergic Ultradian Oscillator (DUO) and the Methamphetamine Sensitive Circadian Oscillator (MASCO)
DUO
DA is the period determinant and the principal oscillator output
The period ranges from 2 - 110 hours
MASCO
Just one slide, no info (check image)
From NCBI: little is known about mechanism but there’s something (SCN-independent) that responds to meth and extends the circadian period of locomotor activity
Describe the model of circadian and ultradian oscillato output integration in health and during hyperdopaminergia
Normal:
24 hour SCN cycle and 4 hour DUO cycle integrate leading to activity peaks during the day and troughs at night
Hyperdopaminergia:
24 hour SCN cycle and 48 hour DUO cycle integrate leading to nighly activity with activity during every second day
When is DUO not phase aligned with the circadian timer/light dark cycle?
When extracellular dopamine levels are altered
Who do DUO dysregulated mice most similar to in terms of temporal patterns of rest:arousal and mood?
Psychopathological patients
What is one representation of the MASCO?
A long-period manifestation of the DUO
