Suprachiasmatic Nucleus Flashcards
How was the SCN established as the circadian pacemaker?
Lesions in SCN disrupted circadian rhythm in mice
Graft of an animal with a FRP of 24 hours (instead of 22) shows resuming of circadian rhythm with new FRP of 24 hours
What proteins/hormones are released by the SCN?
VP VIP CalB GRP 'Cap'
Are all SCN proteins/hormones released homogeneously?
No, different regions secrete different protein
When is Per1 expressed the most in the Dorsomedial region? The Ventrolateral region?
DM: Peak at late day
VL: Peak early morning
When is Per2 expressed the most in the Dorsomedial region? The Ventrolateral region?
DM: Peak at late day
VL: Peak around noon
How does a LD cycle shift affect Per1 RNA expression in the SCN?
Gradual shift of about 1 hr per day
discrepancy between DM and VL regions in terms of catchup time
Does an isolated neuron from the SCN display circadian rhythm? What does this prove?
Yes
Proves that A clock can be contained within a single cell
What was observed when a Cyclohexamide “wedge” experiment was carried out on the SCN?
On a pulse longer than 6 hours protein synthesis stopped, then restarted itself (somehow)
The proteins are able to communicate somehow
What was noticed in Cry1 -/- mice that was not noticed in Cry2 -/- mice?
Dispersed neurons lost their phase whereas cry2 KO still retained some phase
(grouping neurons together rescued wt phenotype though)
What happens to a VIP-Knockout mouse’s Per2 expression? What happens when a healthy SCN is grafted onto the knockout mouse? What does that imply?
VIP KO: amplitude steadily decreases
SCN Graft: Amplitude is restored
Implies that something in the healthy SCN rescues the wild type, and the difference was a VIP KO
In terms of Per expression, the dorsal recion of the SCN expresses Per (before/after) the middle and ventral regions
Before
A lesion of the dorsal and ventromedial SCN showed what activity pattern in each segment?
Dorsal segment was all over the place, Ventromedial segment was completely fine
The dorsal cells themselves are still rhythmic, but they are all out of phase
What SCN region secretes VIP?
Ventral
What happens when VIP receptors are knocked out?
Cells are still rhythmic but desynchronised
How does cAMP factor in with VIP?
Clock has a tight feedback mechanism regulated by VIP
Removing cAMP desynchronizes cells
