Opioid receptor changes in weaver mouse striatum

The dopaminergic projection from the substantia nigra to the patch and matrix compartments of the caudate-putamen undergoes a spontaneous, early postnatal degeneration in mice which carry the weaver gene. The projection to nucleus accumbens is relatively spared. Dopaminergic afferents have been shown to be important modulators of striatal opioid receptor expression. In the present study, opioid receptor localization in the caudate-putamen and nucleus accumbens of control and weaver mice was examined by quantitative autoradiography. Mu, delta and kappa opioid receptors were differentially distributed in nucleus accumbens and in patch and matrix compartments of the caudate-putamen. In animals which were homozygous for the weaver gene, the density of mu opioid receptors in both patch and matrix compartments was unchanged with respect to control mice. In contrast, the density of delta and kappa opioid receptors was significantly decreased in weaver caudate-putamen and nucleus accumbens. The significance of these results with respect to opioid receptor expression and Parkinson's disease is discussed.