Comparative development of striatal opiate receptors and dopamine revealed by autoradiography and histofluorescence

The pattern alignment of dopamine and mu opiate receptors in the rat neostriatum during pre- and postnatal development was investigated by means of catecholamine histofluorescence and receptor autoradiography in alternate sections. On embryonic day (E) 14, dopamine and mu opiate receptors appear in the striatum, but neither is yet distributed in patches. On E19, patches and a lateral rim of intense, punctate dopamine fluorescence begin to form, while patches of dense opiate receptors within a less dense matrix are apparent on E20. From the emergence of patterns in the two systems until the disappearance of dopamine fluorescent patches after postnatal day (P) 16, dopamine and opiate receptor patches in the dorsal striatum are in topographic register. After P16, dopamine fluorescence is diffuse and homogeneous in the dorsal striatum, and opiate receptors continue to mature into their heterogeneous adult pattern. In the accumbens nucleus, opiate receptors appear on E18, whereas dopamine fluorescence is not discerned until E20. The patterning of the two systems in the accumbens nucleus lags behind that of the caudate-putamen, and from P6 through adulthood, areas of dim fluorescence correspond to dense opiate receptor patches. The register of dorsal striatal dopamine and opiate receptors and their negative association in the accumbens nucleus are discussed in relation to dual dopamine and opiate systems. The role that these systems play as developmental determinants is discussed.