Abstract
Adenosine promotes a concentration-dependent hydrolysis of [ 3H]glycogen newly synthesised from [ 3H]glucose by rabbit retinal slices. The EC 50 is 15 μM. Theophylline and 8-phenyltheophylline antagonise the glycogenolysis induced by adenosine. The rank order of efficacy of adenosine agonists is chloroadenosine (CLA) and adenosine > d- phenylisopropyl- adenosine ( d- PIA) > l- PIA > N- ethyl- carboxamidoadenosine ( NECA) > cyclohexyladenosine (CHA), suggesting that adenosine promotes glycogenolysis via receptors of the A 2 type. This is supported by the finding that the rank order of effectiveness of adenosine agonists for stimulating C-AMP production is similar to that found for glycogenolysis though NECA is more efficacious than d-PIA and l-PIA. In addition, the weak stereospecificity observed for the glycogenolytic action d-PIA and l-PIA provides further support. It is suggested that some A 2-receptors exist on Müller cells of the retina and that adenosine has a modulatory role in the retina, coupling neuronal activity and energy metabolism in the Müller cells.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
