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BioMed Research International
Volume 2015 (2015), Article ID 872684, 9 pages
http://dx.doi.org/10.1155/2015/872684
Research Article

The Combined Inhibitory Effect of the Adenosine A1 and Cannabinoid CB1 Receptors on cAMP Accumulation in the Hippocampus Is Additive and Independent of A1 Receptor Desensitization

1Health Sciences Research Center, University of Beira Interior (CICS-UBI), Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal
2Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Avenida Professor Egas Moniz, 1649-028 Lisbon, Portugal
3Unit of Neurosciences, Institute of Molecular Medicine, University of Lisbon, Avenida Professor Egas Moniz, 1649-028 Lisbon, Portugal
4Department of Chemistry, University of Beira Interior, Rua Marquês D’Ávila e Bolama, 6201-001 Covilhã, Portugal

Received 5 September 2014; Revised 5 December 2014; Accepted 21 December 2014

Academic Editor: George Perry

Copyright © 2015 André Serpa et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Adenosine A1 and cannabinoid CB1 receptors are highly expressed in hippocampus where they trigger similar transduction pathways. We investigated how the combined acute activation of A1 and CB1 receptors modulates cAMP accumulation in rat hippocampal slices. The CB1 agonist WIN55212-2 (0.3–30 M) decreased forskolin-stimulated cAMP accumulation with an EC50 of 6.6 ± 2.7 M and an of 31% ± 2%, whereas for the A1 agonist, N6-cyclopentyladenosine (CPA, 10–150 nM), an EC50 of 35 ± 19 nM, and an of 29% ± 5 were obtained. The combined inhibitory effect of WIN55212-2 (30 M) and CPA (100 nM) on cAMP accumulation was 41% ± 6% (), which did not differ () from the sum of the individual effects of each agonist (43% ± 8%) but was different () from the effects of CPA or WIN55212-2 alone. Preincubation with CPA (100 nM) for 95 min caused desensitization of adenosine A1 activity, which did not modify the effect of WIN55212-2 (30 M) on cAMP accumulation. In conclusion, the combined effect of CB1 and A1 receptors on cAMP formation is additive and CB1 receptor activity is not affected by short-term A1 receptor desensitization.