Localization of dopamine D1A and D1B receptor mRNAs in the forebrain and midbrain of the domestic chick

The distribution and cellular localization of dopamine D1A and D1B receptor mRNAs in the forebrain and midbrain of the domestic chick were examined us ing in situ hybridization histochemistry with (35)[S]-dATP labeled oligonuc leotide probes, visualized with film and emulsion autoradiography. Labeling for DIA receptor mRNA was intense in the medial and lateral striatum, and moderately abundant in the pallial regions termed the archistriatum and the neostriatum, in the hypothalamic paraventricular nucleus region, and in th e superficial gray layer of optic tectum of the midbrain. D1B receptor mRNA was abundant in the medial and lateral striatum, and in the pallial region termed the hyperstriatum ventrale, and moderately abundant in the intralam inar dorsal and posterior thalamus and in the superficial gray of the optic tectum. At the cellular level, about 75% of neurons in the medial striatum and 59% of neurons in the lateral striatum were labeled for D1A receptor m RNA, whereas about 39% of the neurons in the medial striatum and 21% in the lateral striatum were labeled for DIB receptor mRNA. Large striatal neuron s were not labeled for D1A or D1B receptor mRNA. The data suggest that whil e both D1A and D1B receptors mediate dopaminergic responses in many neurons of the avian striatum, primarily DIA receptors mediate dopaminergic respon ses in the archistriatum and the neostriatum, while primarily DIB receptors mediate dopaminergic responses in the hyperstriatum ventrale and the thala mus. (C) 2000 Elsevier Science B.V. All rights reserved.