The inhibitory effects of some adenosine analogues on transmitter release at the mammalian neuromuscular junction.
An electrophysiological study was made of the effects of four adenosine analogues, 2-chloroadenosine (2-CIA), 5'-N-ethylcarboxamidoadenosine (NECA), L-N6-phenylisopropyladenosine (L-PIA), and 2-(p-methoxyphenyl)-adenosine (CV-1674) on neurotransmitter release in the mouse phrenic nerve - hemidiaphragm preparation. All four drugs decreased miniature end-plate potential frequency in a dose-dependent manner. Evoked transmitter release in the cut diaphragm preparation was depressed by 2-CIA and CV-1674 to a similar extent. The ability of theophylline to antagonize the inhibitory effect of CV-1674 on spontaneous transmitter release was also established. On the basis of these results, the rank order of potencies was: L-PIA greater than NECA greater than 2-CIA greater than CV-1674. A clear classification of receptor type could not be made, since the ratio of potencies of L-PIA and NECA was narrow. Different slopes of the concentration-effect curves for 2-CIA and CV-1674 compared with L-PIA and NECA suggest an additional component to simple agonist action in their overall effects.
D015762:2-Chloroadenosine; D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009469:Neuromuscular Junction / Q000187:drug effects*; D011983:Receptors, Purinergic / Q000145:classification / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects*; D013806:Theophylline / Q000494:pharmacology
D011983:Receptors, Purinergic; D015762:2-Chloroadenosine; C015606:2-(p-methoxyphenyl)adenosine; D013806:Theophylline; D000241:Adenosine