Densities of dopamine D2 receptors are reduced in CNS regions of alcohol-preferring P rats.

The densities of dopamine D2 recognition sites labelled with [3H]sulpiride were determined in the caudate-putamen, nucleus accumbens (medial and lateral portions), olfactory tubercle, substantia nigra (pars reticulata and pars compacta), and ventral tegmental area (VTA) of alcohol-naive, selectively bred P (N = 7) and NP (N = 7) rats using quantitative autoradiography. The binding of [3H]sulpiride was 20-25% lower (P < 0.05) in the caudate-putamen, medial and lateral nucleus accumbens, and VTA of the P compared with the NP rats. No significant differences were observed between the P and NP rats in the olfactory tubercle or substantia nigra. [3H]Sulpiride binding, using standard membrane preparations, established with Scatchard analysis that the difference in the densities of D2 recognition sites in the caudate-putamen between the P and NP rats was due to lower Bmax values for the P line. The results indicate that the number of dopamine D2 receptor sites is lower in several central nervous system regions of the P rats compared to NP rats.