4. -> After exposure to an agonist, the initially maximum response is seen. -> Now if we continue to administer agonist it shows decrease in response due to desensitization of receptors. -> Removal of the drug for a more extended period allows the cell to recover its capacity to respond.
5.
6. -> When agonist is administered continuously,desensitization of the receptor results ; when agonist falls below a certain threshold,the system again becomes sensitive. -> E.G. Think of whathappens to your visual transduction system when you walk from bright sunlight into a darkened room or from darkness into the light. Lehninger principles of biochemistry 4th Edition pg.427
7. Five ways by which target cells can become desensitized to a signal molecule. http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mboc4.figgrp.2792
20. Desensitization of the β –adrenergic receptor in the continued presence of epinephrine. This process is mediated by two proteins: - Β - adrenergic protein kinase (ARK) & β -arrestin (arr ; arrestin 2). Lehninger principles of biochemistry 4th Edition pg.440
34. imaging of endogeneous adenosine receptors internalization Department of Phsyiology & Pharmacology Receptor Biology & SignalingKarolinska Institutet, Stockholm