Adenosine and dopamine receptor antagonist binding in the rat ventral and dorsal striatum:: lack of changes after a neonatal bilateral lesion of the ventral hippocampus

There is experimental evidence from radioligand binding experiments for the existence of strong antagonistic interactions between different subtypes of adenosine and dopamine receptors in the striatum, mainly between adenosine Al and dopamine D-1 and between adenosine A(2A) and dopamine D-2 receptors. These interactions seem to be more powerful in the ventral compared to the dorsal striatum, which might have some implications for the treatment of schizophrenia. The binding characteristics of different dopamine and adenosine receptor subtypes were analysed in the different striatal compartments (dorsolateral striatum and shell and core of the nucleus accumbens), by performing saturation experiments with the dopamine DI receptor antagonist [I-125]SCH-23982. the dopamine D2-3 receptor antagonist [H-3]raclopride, the adenosine Al receptor antagonist [H-3]DPCPX and the adenosine A(2A) receptor antagonist [H-3]SCH 58261. The experiments were also performed in rats with a neonatal bilateral lesion of the ventral hippocampus (VH), a possible animal model of schizophrenia. Both dopamine D2-3 and adenosine A(2A) receptors follow a similar pattern, with a lower density of receptors (40%) in the shell of the nucleus accumbens compared with the dorsolateral caudate-putamen. A lower density of adenosine A(1) receptors (20%) was also found in the shell of the nucleus accumbens compared with the caudate-putamen. On the other hand, dopamine D-1 receptors showed a similar density in the different striatal compartments. Therefore, differences in receptor densities cannot explain the stronger interactions between adenosine and dopamine receptors found in the ventral, compared to the dorsal striatum. No statistical differences in the binding characteristics of any of the different adenosine and dopamine receptor antagonists used were found between sham-operated and V-H-lesioned rats. (C) 1999 Elsevier Science Ltd. All rights reserved.