Expression of adenosine A1 receptors in cultured neurons from fetal rat brain.

The expression of adenosine A1 receptors was investigated using [3H]2-chloro-N6-cyclopentyladenosine (CCPA) in 8-day-old cultured neurons from fetal rat forebrain grown in serum-free medium. [3H]CCPA bound specifically and with high affinity (Kd = 2.9 nM) to a homogeneous population of sites. Displacement of CCPA binding by various adenosine derivatives indicated that A1 receptors were selectively labeled. The presence of Gpp(NH)p, a GTP analogue, reduced significantly the binding affinity (Kd = 12.2 nM), suggesting that A1 receptors detected in intact cultured cells are linked to associated G proteins.