Expression levels of adenosine receptors in hippocampus and frontal cortex in argyrophilic grain disease

Expression of adenosine receptors of the A1, A2A and A2B type has been examined in the post-mortem frontal cortex and hippocampus in argyrophilic grain disease (AGD), a tauopathy affecting the hippocampus but usually not the frontal cortex, in an attempt to learn about the modulation of the adenosine pathway in this disorder. Significant increased levels of A1, but not of A2A and A2B, have been observed in AGD in the hippocampus but not in the frontal cortex, when compared with age-matched controls. This is accompanied by increased levels of adenylyl cyclase (AC), an effector of A1, and by increased (although not significant) percentage of inhibition of forskolin-stimulated AC by the A1 agonist cyclohexyladenosine in the hippocampus in AGD. These findings indicate sensitization of A1/AC in the hippocampus in AGD, and support a putative activation of the A1/AC pathway that may facilitate protection of this preferentially involved region in AGD.