Ovariectomy (OVX) has been widely used to explore the effect of ovarian hormones on brain regions. It has been observed that estrogen in OVX rats increases the dopaminergic function in nucleus accumbens (NAcc). To determine whether absence or presence of estradiol changes the dendritic structure of some dopaminergic neurons, we investigated the consequences of a daily injection for 2 weeks of 17-beta estradiol (E2) on the dendritic morphology of NAcc neurons in two groups of rats, immediately or 10 weeks administered after OVX. The structure of dendrites was measured by using the Golgi-Cox procedure followed by a Sholl analysis. We found a reduction in the number of spiny dendrites of the medium spiny neurons of the NAcc in animals in which E2 was administrated without delay after OVX. However, when the same treatment was administered 10 weeks after OVX, not any difference was observed. Independently of the hormone treatment, rats from the group of 10 weeks after OVX showed a reduction in the number of spiny dendrites of the medium spiny neurons when compared with their counterparts at 2 weeks. Data suggest that estrogens or their absence regulate synaptogenesis in the NAcc.