Adenosine A₁ receptors (A₁ARs) are promising imaging biomarkers and targets for the treatment of stroke. Nevertheless, the role of A₁ARs on ischemic damage and its subsequent neuroinflammatory response has been scarcely explored so far.

Methods: In this study, the expression of A₁ARs after transient middle cerebral artery occlusion (MCAO) was evaluated by positron emission tomography (PET) with [¹⁸F]CPFPX and immunohistochemistry (IHC). In addition, the role of A₁ARs on stroke inflammation using pharmacological modulation was assessed with magnetic resonance imaging (MRI), PET imaging with [¹⁸F]DPA-714 (TSPO) and [¹⁸F]FLT (cellular proliferation), as well as IHC and neurofunctional studies.

Results: In the ischemic territory, [¹⁸F]CPFPX signal and IHC showed the overexpression of A₁ARs in microglia and infiltrated leukocytes after cerebral ischemia. Ischemic rats treated with the A₁AR agonist ENBA showed a significant decrease in both [¹⁸F]DPA-714 and [¹⁸F]FLT signal intensities at day 7 after cerebral ischemia, a feature that was confirmed by IHC results. Besides, the activation of A₁ARs promoted the reduction of the brain lesion, as measured with T2W-MRI, and the improvement of neurological outcome including motor, sensory and reflex responses. These results show for the first time the in vivo PET imaging of A₁ARs expression after cerebral ischemia in rats and the application of [¹⁸F]FLT to evaluate glial proliferation in response to treatment.

Conclusion: Notably, these data provide evidence for A₁ARs playing a key role in the control of both the activation of resident glia and the de novo proliferation of microglia and macrophages after experimental stroke in rats.