mcb 186 circadian biology circadian photoreception uses different receptors and pathways from vision...
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MCB 186CIRCADIAN BIOLOGY
CIRCADIAN PHOTORECEPTION USES DIFFERENT RECEPTORS and PATHWAYS FROM VISION
October 26, 2005J. W. Hastings
HOW DOES LIGHT ENTRAIN THE CIRCADIAN CLOCK?
Action spectra should reveal the photoreceptor molecules involved
What is the “action”?
Phase shifts; Tau; Amplitude of Rhythms
DOES CIRCADIAN PHOTORECEPTION USE THE SAME MOLECULES AS FOR
OTHER PHOTORESPONSES?
e.g.,PHOTOTAXIS, PHOTOMOVEMENT, VISION
The HORSESHOE CRAB Limulus polyphemus
SEVERAL PAIRS of EYES; ALL PARTICIPATE in CLOCK
PHOTORECEPTION but TELSON (TAIL) RECEPTORS are DOMINANT
THE SEVERAL EYES and MANY
PHOTORECEPTORS of the HORSESHOE CRAB
Limulus
Barlow, Scientific American, April 1990
All receptors have phase shifting effects on circadian rhythm; most effective are those in the tail
Renniger et al.1988 J. Comp.Physiol 162: 127-140
PHASE SHIFTING by LIGHT ONLY to the TAILRenniger et al.1988 J. Comp.Physiol 162: 127-140
Horseshoe Crab Limulus
PHASE RESPONSE CURVE for LIGHT PULSES TO TAIL
Limulus Renniger et al.1988 J. Comp.Physiol 162: 127-140
Replace Vitamin A in Rhodopsin with an analog in Chlamydomonas Foster et al 1984 Nature 311: 756-759
Since the absorption spectra are different the action spectra should differ
Drosophila NO EFFECT of NO beta CAROTENE on CIRCADIAN PHOTORECEPTION Zimmerman & Goldsmith Science 1980
EYES REMOVED; LIGHT ENTRAINMENT VIA BRAIN (Menaker,1970)
feathers plucked
1. from back
2. from head
3. feathers growing back; replucked
4. India ink under skin on head
5. ink removed