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PSY397 Oct 15

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Martin Ralph

Lecture 9 10/15/2012 7:06:00 AM Slide 3 – MISSED STUFF  Circadian rhythms are good at determining seasonality o used to capture birds – sparrow (doesn’t migrate all the time)  Does the sparrow have a clock? Slide 4 Slide 5 – Demonstrates perch hopping  Strongly diurnal  If you know where they are, then you can capture them at night  In the daytime you have them hopping around  they don’t re-entrain instantaneously  Therefore, there is an oscillator  They remain rhythmic in DD  Where is the clock located?  Arnold – did an number of experiements taking a look at the eyes o Looking for clock in the eyes o in birds: only obvious photoreceptors o Looked at lateral eyes  he took the eyes out – found: o Put the animals back in: still synchronized with the light o Initial response: photoreceptors not in the eyes o then after a week , the animals started free-running, suggesting that he did take the photoreceptors out  photoreceptors in the eyes, clock in the brain (disconnected from entraining center)  Eyes are the photoreceptors  Why did the animal behave as though synchronized with light cycle? o Maybe he did a surgery and cleaned off feathers and then feathers grew back o Maybe another photoreceptor hidden by feathers o Then eyes have something to do with entrainment o But there is something else in the animal that has something to do with the top of the head and you can change entrainment patterns by shaving the animal’s head again Slide 6 – Sue Gaston looked at anatomy of the bird  there is only one thing on the top of the head that could possibility have something to do with photoreceptors  noticed pineal gland Slide 7 – Removed pineal gland  Hypothesis_ this is the photoreceptor  Animals already free running in the dark, become arrhythmic Slide 8 – top: animals free running in the dark and put them in the light again  Found they still synchronize with the light cycle even though they were arrhythmic in the dark  Maybe there is another osciallator that can synchronize with the light cycle  Or there is another photorrecptor  Both are correct Sldie 9 – Pineal removed in light cycle  Bottom – in DD and is arrhythmic  Middle – put back into DD where arrow is, but it takes 5 or 6 days to become arrhythmic  Thereofre, there is evidence for another oscillator expressed in the DD that can be synchronized with the light cycle o not a persistent oscillator when pineal gland is not there o Pineal gland is necessary for normal expression of free run in DD o But you also find evidence of another clock Slide 10 – Is the pineal gland a clock  Natille Zimmerman – transplant experiment  Moved the clock from one animal to another Slide 11 – First step – show that you can do a transplant  this animal is arrhythmic in DD and gets a new pineal and it produces a rhythm  Transplanted into the eye (to protect it from the immune system of the host) Slide 12 - now did phase transplant experiment  second section: pineal glands removed  Thrid section: received new pineal gland o Phase reflects the phase of the donor o therefore, the pineal gland can carry information of phase, maybe not period, but phase Slide 13 - now we need to know about pineal gland itself (it can still contain an oscillator, but maybe not the main oscillator)  SCN – required to expressing circadian rhythms  Is there another oscillator somewhere else?  Found if you lesion SCN, the birds beco
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