Altered levels of synapsin I, dopamine transporter, dynorphin A, and neuropeptide Y in the nucleus accumbens and striatum at post-puberty in rats treated neonatally with pregnenolone or DHEA

It is well documented that neonatal neurosteroid administration influences brain development. In our previous studies, administration of pregnenolone, the precursor of neurosteroids, during the neonatal period altered the activity of dopamine (DA) in the striatum. Furthermore, neonatal treatment with pregnenolone or dehydroepiandrosterone (DHEA) increased synapse-related protein synapsin I as well as neuropeptide Y (NPY) in the hippocampus. The present study examined the effects of neonatal treatment with pregnenolone or DHEA on synapsin I, DA transporter (DAT), dynorphin A, and NPY in the striatum and the core and shell of the nucleus accumbens at post-puberty. Administration of pregnenolone or DHEA during the neonatal period increased immunodensity of synapsin I in the dorsomedial or ventrolateral striatum. DAT immunodensity in the striatum and the nucleus accumbens core as well as dynorphin A immunodensity in the nucleus accumbens core were increased in DHEA-treated but not in pregnenolone-treated rats. In addition, the size, but not numbers, of NPY-positive cells in the nucleus accumbens core was increased in pregnenolone- and DHEA-treated rats. The results suggest that neurosteroid levels during the neonatal period have larger impact on synaptic formation, development of DA and NPY systems in the nigrostriatal rather than the mesolimbic pathway.