N6-cyclohexyl[3H]adenosine, ([3H]CHA), was used to label adenosine a1 receptors in crude synaptic membranes prepared from rat and guinea pig brain. The density of [3H]CHA binding sites was highest in the rat hippocampus and cerebellum and in the guinea-pig hippocampus. A microdissection of coronal sections of guinea-pig hippocampus revealed that the specific binding capacity for [3H]CHA in area CA-1 was 20-30% higher than in area CA-3, dentate gyrus and subiculum. Selective neuronal lesions of serotonergic, noradrenergic and cholinergic afferents to the hippocampus failed to alter [3H]CHA binding to hippocampal membranes. These results suggest that [3H]CHA binding sites are not associated with axons or terminals of these neurones in the hippocampus. Intrahippocampal injection of kainic acid reduced the number of [3H]CHA recognition sites by 30% with no alteration in the affinity of [3H]CHA for these receptors. Thus, a significant portion of A1 receptors may be associated with intrinsic neurones of the hippocampus which do not appear to be innervated by noradrenergic, cholinergic or serotonergic axons.
All Science Journal Classification (ASJC) codes
- Cellular and Molecular Neuroscience