Effects of prolactin on tyrosine hydroxylase activity of central dopaminergic neurons of male rats

Previous work from our laboratory has indicated that ovine prolactin can produce a rapid stimulation (within 1 h) of dopamine release from nigrostriatal and mesolimbic dopaminergic neurons of male rats. In the present experiment we attempted to determine whether this effect of prolactin was a function of an increase in the activation of dopamine synthesis. To examine this possibility we used the drug NSD 1015. This drug is a decarboxylase inhibitor that leads to dopa accumulation and is used as an index of in vivo tyrosine hydroxylase activity. Our results demonstrated that ovine prolactin increased turnover of dopamine but had no effect upon tyrosine hydroxylase activation (up to 4 h) in both dorsal and ventral striatal dopaminergic neurons. In contrast, ovine prolacting had a clear effect (within 4 h) on tyrosine hydroxylase activity in mediobasal hypothalamic dopaminergic neurons. These results suggest that ovine prolactin can differentially alter synthesis/release processes of dopamine from these sites.