| Summary: | Hibernation is an adaptation that allows the Arctic ground squirrel (Urocitellus parryii) to survive the harsh arctic winter. Recently the activation of the Adenosine A1 receptor (A₁AR) has been shown to be necessary for entrance into hibernation during the winter but not summer season. In the current study we characterize the A₁AR in the forebrain, hippocampus and hypothalamus of summer and winter AGS. We also tested the hypothesis that increased A₁AR agonist efficacy is responsible for increased sensitization of the A₁AR during the winter season. The resulting ³⁵S-GTPγS binding data indicated an increase in agonist potency during the winter season in all three brain regions. A plausible explanation of our results is that increased potency in the forebrain during the winter season is due to an increase in efficacy as indicated by a greater number of receptors in the high affinity state. In addition ³⁵S-GTPγS binding, [³H] DPCPX saturation and competition assays establish for the first time pharmacological characteristics such as EC⁵⁰, Kd, Kilo and Kihi in AGS brain.
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