Comparison of dopamine binding sites in the rat superior cervical ganglion and caudate nucleus.

A comparison of morphological and biochemical characteristics of the D1-type dopamine receptor has been assessed in two experimental tissues, the superior cervical ganglion (SCG) and caudate nucleus of the rat. Correlation of the distribution of this dopaminergic binding site using in vitro autoradiographic localization of [3H]SCH 23390, a selective D1-binding antagonist, demonstrated no specific association of this receptor subtype with cyclic AMP immunoreactive structures in the superior cervical ganglion. In contrast, the caudate nucleus demonstrated specific D1-binding sites associated with cyclic AMP immunoreactive elements. Biochemical analyses of the D1-dopamine binding sites showed only 20% of the amount of radioligand bound in SCG homogenates as compared to the quantity bound in homogenates of the caudate nucleus. The non-cyclase linked dopaminergic receptor, assessed using D2-type radioligand binding, was much less prevalent than the binding of the D1-subtype in either experimental tissue. Only a small amount of [3H]sulpiride binding, indicative of the D2-receptor subtype, could be measured in the SCG as compared to the caudate nucleus. This work has demonstrated differences in the amount, and the cellular association of dopamine binding sites in peripheral versus central nervous system areas with dopamine sensitive adenylate cyclase mechanisms.