Ovariectomy reduces the dendritic spine density of the dorsal raphe neurons in the adult rat

Background – The sex steroid hormones play a significant role in modulating postnatal neuronal maturation, synaptology, and neural circuit formation. Female gonadal steroids are known to influence serotonergic system physiology in adulthood. We aimed at finding out if gonadal steroids influence the morphology of dorsal raphe neurons in the intact adult rat brain. Methods – Golgi impregnation was performed on brainstems of ovariectomized (OVX) rats to determine whether female sex hormones influence dorsal raphe neuronal morphology in the intact adult rat brain. Results – Removal of circulating gonadal sex steroids by ovariectomy resulted in significant decrease in primary and secondary dendritic spine density of the dorsal raphe neurons in adult female rats. These findings demonstrate that gonadal steroids are necessary for the maintenance of normal adult cell structure and plasticity of dorsal raphe nucleus. Conclusion – It is suggested that the gonadal steroids are able to affect the synaptic organization, connectivity, and plasticity, and also exert a generalized action on the serotonergic system, thereby influencing a number of brain functions and behaviors.