Reduced DAT- and DBH-immunostaining in the limbic system of Sardinian alcohol-preferring rats

We have recently shown that tyrosine-hydroxylase immunostaining (TH-IM) is selectively decreased in the cingulate cortex and in the shell of the nucleus accumbens (nAcc) of Sardinian alcohol-preferring rats (sP) when compared with Sardinian alcohol-non preferring (sNP) and Wistar (W) rats. Since these regions contain both dopamine and noradrenaline (NA) fibers, clarification of the dopaminergic and noradrenergic contribution to the decreased TH-immunoreactivity was needed. To this aim, we carried out the present immunohistochemistry study using two antibodies raised against dopamine beta-hydroxylase (DBH), the enzyme responsible for the conversion of dopamine into noradrenaline, and against the dopamine transporter (DAT), as markers for noradrenergic and dopaminergic fibers, respectively. The results show that DBH-immunostaining (DBH-IM) and DAT-immunostaining (DAT-IM) were both lower in the cingulate cortex of the sP rats with respect to sNP and W rats. In the shell of the nAcc a reduced DAT-IM in sP rats was found, while the DBH-IM did not differ between the three lines of rats. The analysis of the cell-body area of noradrenergic neurons in the locus coeruleus, revealed no differences between sP, sNP and W rats. These results indicate a selective reduction of the terminal innervation in the mesocorticolimbic dopamine and NA systems in sP rats. This genetically-determined difference may be involved in the opposite alcohol preference and consumption of sP and sNP rats.