Characterization of the locomotor depression produced by an A2-selective adenosine agonist.
Adenosine analogs, such as N6-cyclohexyladenosine (CHA) that are selective for A1-adenosine receptors, and analogs, such as 5'-N-ethylcarboxamidoadenosine (NECA) that are active at both A1 and A2 receptors, cause a profound depression of locomotor activity in mice via a central mechanism. The depression is effectively reversed by non-selective adenosine antagonists such as theophylline. We report that 2-([2-aminoethylamino) carbonylethylphenylethylamino]-5'-N-ethylcarboxamidoadenosine (APEC), an amine derivative of the A2-selective agonist, CGS21680, is a potent locomotor depressant in mice. The in vivo pharmacology is consistent with A2-selectivity at a central site of action. Two parameters indicative of locomotor activity, horizontal activity and total distance travelled, were measured using a computerized activity monitor. From dose-response curves it was found that APEC (ED50 16 micrograms/kg) is more potent than CHA (ED50 60 micrograms/kg) and less potent than NECA (ED50 2 micrograms/kg). The locomotor depression by APEC was reversible by theophylline, but not by the A1-selective antagonists 8-cyclopentyltheophylline (CPT) and 8-cyclopentyl-1, 3-dipropyl-2-thioxanthine, nor by the peripheral antagonists 8-p-sulfophenyltheophylline (8-PST) and 1,3-dipropyl-8-p-sulfophenylxanthine. The locomotor activity depression elicited by NECA and CHA was reversed by A1-selective antagonists. These results suggest that the effects of APEC are due to stimulation of A2 adenosine receptors in the brain.
Nikodijević
O
O
Laboratory of Chemistry, National Inst. of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
Daly
J W
JW
Jacobson
K A
KA
D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide); D000818:Animals; D008297:Male; D051379:Mice; D015394:Molecular Structure; D009043:Motor Activity / Q000187:drug effects*; D010627:Phenethylamines / Q000494:pharmacology*; D011983:Receptors, Purinergic / Q000187:drug effects / Q000502:physiology*; D013806:Theophylline / Q000494:pharmacology
D010627:Phenethylamines; D011983:Receptors, Purinergic; C063208:2-((2-aminoethylamino)carbonylethylphenylethylamino)-5'-N-ethylcarboxamidoadenosine; D019830:Adenosine-5'-(N-ethylcarboxamide); C027513:N(6)-cyclohexyladenosine; D013806:Theophylline; D000241:Adenosine