Circadian Rhythms

Question 1

SCN neuropeptides

Answer 1

• SCN = core and shell subdomains
• core uses VIP and GRP
• shell uses AVP
• AVP signalling is necessary for SCN robustness = prevents swaying of circadian rhythm in response to minor environmental changes
• AVP KO prevents jet lag

Question 2

SCN signals - nocturnal versus diurnal

Answer 2

• SCN signals in mice and humans are the same
• nocturnal animals must have an invertor somewhere
• to cause behavioural rhythms to be offset by 12 hours

Question 3

SCN

Answer 3

• suprachiasmatic nucleus
• the mammalian master clock
• SCN is in the hypothalamus
• ablation of SCN in mice = recover fine but have no endogenous rhythm in constant conditions
• SCN exhibits circadian rhythms in gene expression ex vivo
• fetal SCN grafts partially restore circadian behaviours = intrinsic period restored is determined by the genotype of the graft, not the host!
• SCN is sufficient and necessary for circadian behaviours