Neurotransmitter receptors in the avian brain. I. Dopamine receptors

The distribution of dopamine D1 and D2 receptors was investigated in the pigeon brain using in vitro receptor autoradiography. D1 receptors were labeled in slide-mounted tissue sections with [3H]SCH 23390. The agonist [3H]CV 205-502 and the antagonist [3H]spiroperidol were used to label D2 receptors. The highest densities of both D1 and D2 receptors were concentrated in the paleostriatum augmentatum, lobus paraolfactorius and olfactory tubercle. D1 receptors were in addition enriched in the entire pigeon telencephalon with exception of the ectostriatum. In contrast, no significant densities of D2 receptors were observed in the pallium. D2 but not D1 receptors were present in the tectum and nucleus pretectalis. The cerebellum presented D1 but not D2 receptors. These results demonstrate that in the avian brain, like in the mammalian one, both dopamine D1 and D2 receptors are concentrated in 'striatal' areas, while the telencephalon is rich in D1 but not D2 receptors.