Non-Selective Effects of Adenosine A 1 Receptor Ligands on Energy Metabolism and Macromolecular Biosynthesis in Cultured Central Neurons

Abstract

To investigate the effects of adenosine A 1 receptor activation on energy metabolism and RNA and protein biosynthesis in central neurons, cultured neurons from the rat forebrain were exposed for 1 hr to 72 hr to various concentrations (10 nM–100 μM) of the selective A 1 receptor agonist 2-chloro- N 6-cyclopentyladenosine (CCPA) or the A 1 receptor antagonist 8-cyclopentyltheophylline (CPT). At all concentrations tested, the adenosinergic compounds did not affect cell viability within 72 hr of treatment, except for CPT, which reduced viability by 19.7% when used at the concentration of 100 μM. Energy metabolism was analysed by studying the specific uptake of 2-D-[ 3H]deoxyglucose ([ 3H]2DG). Rates of RNA and protein biosynthesis were assessed by the measurement of [ 3H]uridine and [ 3H]leucine incorporation, respectively. Neuronal [ 3H]2DG uptake was increased by 16% ( P < 0.01) after 8 hr in the presence of 100 μM CCPA, whereas 100 μM CPT for 24 hr also increased [ 3H]2DG uptake (8%, P < 0.01). At these concentrations, both ligands inhibited [ 3H]uridine incorporation after a 3-hr treatment by 92% and 30%, respectively. CCPA never altered [ 3H]leucine incorporation when compared to controls, and CPT significantly inhibited protein synthesis only at 10–100 μM. Additional experiments to analyse the influence of A 1 ligands on the transport of [ 3H]2DG, [ 3H]leucine and [ 3H]uridine suggested that CCPA and CPT, which interact functionally with adenosine receptors by regulating cyclic AMP production in this model, are able to alter energy metabolism and RNA synthesis in central neurons in a nonspecific manner by interacting with glucose and uridine transporters.