Synapse Homework Part II Slides 2009

Synapse Homework Part II Slides 2009 - Synapse Homework...

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Synapse Homework Part II John Troy and Aaron Cunningham * Biomedical Engineering Department Northwestern University (* VaNTH REU student from Cornell University, summer 2006)
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In the brain caffeine acts as an antagonist to adenosine. Adenosine is generally considered a neuromodulator. Once absorbed caffeine, moves in the blood stream, crosses the blood-brain barrier and enters the brain’s interstitial space. Because adenosine is not released via a calcium dependent process or packaged in synaptic vesicles we cannot consider adenosine to be a neurotransmitter. Picture taken from http://www.fi.edu/brain/index.htm From http://www.donotgiveup.net/coffee%20addiction.jpg
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Caffeine and adenosine Caffeine Adenosine From Chemfinder The adenine portion of adenosine has a chemical structure like that of caffeine. Thus caffeine can bind to and block adenosine receptors. ATP in cells is their main source of biochemical energy. The energy is released by converting ATP to first ADP, then AMP and finally adenosine. As we will see, adenosine is not simply a waste product.
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Adenosine is produced intracellularly by the hydrolysis of AMP. The hydrolysis of S-adenosyl- homocysteine (SAH) by SAH hydrolase also contributes to intracellular adenosine, but this contribution is relatively minor. Adenosine From Chemfinder Adapted from Dunwidde, T.V. and Masino, S.A. (2001) The role and regulation of adenosine in the central nervous system. Annual Review of Neuroscience 24 31-55.
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Adenosine is also synthesized outside the cell by ATP degradation through an ecto – nucleotidase chain. Ecto- nucleoside triphosphate diphosphohydrolases (E- NTPDases) cause the extracellular degradation of ATP. NTPDase1 reduces ATP to AMP and AMP is reduced to adenosine by ecto 5’-nucleotidase. Extracellular adenosine production More than 90% of total adenosine production occurs Intracellularly.
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Due to high intracellular rates of rephosphorylation and deamination [adenosine] inside is less than [adenosine] outside , creating a concentration gradient. This gradient causes adenosine to enter the cell by facilitated diffusion. Adenosine production intracellularly and extracellularly is counter-balanced by degradation pathways
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extracellular adenosine results from ATP degradation following vesicular release. 1. Equilibrative transport proteins act by facilitative diffusion allowing adenosine to move down its concentration gradient. 2. Concentrative transporters use the sodium concentration gradient to actively transport adenosine, generally against the adenosine concentration gradient. ATP
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This note was uploaded on 01/12/2011 for the course BME 301 taught by Professor Li during the Fall '10 term at Northwestern.

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Synapse Homework Part II Slides 2009 - Synapse Homework...

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