Effects of dopamine and estrogen upon cortical neurons that express parvalbumin in vitro

The purpose of these experiments was to study the effects of dopamine (DA) and 17 beta-estradiol (EST) upon parvalbumin expression in rodent frontal cortex during development. Organotypic slice cultures of the frontal cortex were prepared from neonatal rats (postnatal day 2/3) and maintained for 14 days in vitro in serum-enriched medium and medium treated with either DA, EST or DA+EST. Cultured slices were then fixed and immunostained for parvalbumin immunoreactivity. Under control conditions, parvalbumin immunoreactive somata and fibers were primarily found in the deep laminae. In comparison, slices in all treatment groups exhibited a pattern of parvalbumin expression that was significantly different than controls. Specifically, DA treatment increased the percentage of parvalbumin immunoreactive somata, dendritic length and density in the deep cortical layers, but not in the superficial cortical layers. Both EST and DA+EST treatments induced similar changes in both the deep and the superficial cortical layers. These treatment induced changes represent more mature patterns of parvalbumin expression when compared to controls, indicating that both DA and EST enhance cortical expression of the protein.