Gender Differences in the Neurobiology of Anxiety: Focus on Adult Hippocampal Neurogenesis

Box 1

Estrous cycle.

The estrous cycle consists of the reproductive cycle of females. It lasts four to five days

and is divided into four phases: proestrus, estrous, metaestrus, and diestrus [103]. It can be

identified by cytological analysis according to the proportion and cell types in the

vaginal secretion [104].

Each phase of the cycle lasts around 24 hours and is mainly linked to fluctuations in

estradiol levels, which begins at puberty and ends in senescence (about 12 months in

female rats). The metaestrus and diestrus phases have low level concentrations of serum

estradiol. The proestrus is characterized by the highest level of estradiol followed by the

estrous phase, where levels of the hormone start to decrease, coinciding with ovulation

and corpus luteum formation [105].