The objective of this study was to characterize the effects of the adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) and its low efficacy derivatives 2′-deoxy-CPA (2DCPA), 3′-deoxy-CPA (3DCPA), 8-ethylamino-CPA (8ECPA) and 8-butylamino-CPA (8BCPA) on the release of acetylcholine (ACh) using intrastriatal microdialysis. These low efficacy agonists exhibited lower effects on the cardiovascular system than CPA. A concentration-dependent inhibition of ACh release was observed with a maximum of 60.5±2.4% for CPA, 42.5±2.3% for 2DCPA, 45.3±5.8% for 3DCPA, 57.1±1.4% for 8ECPA and 93.1±10.9% for 8BCPA, respectively. This effect was counteracted by the adenosine A1 receptor antagonist 8-cyclopentyltheophylline. These findings show that low efficacy adenosine A1 agonists inhibit striatal ACh release equally effective as CPA, suggesting that central nervous system-selective actions can be obtained with these compounds. © 2003 Elsevier Science Ireland Ltd. All rights reserved.