ReviewSexual differentiation of the adolescent rodent brain: Hormonal influences and developmental mechanisms
Section snippets
Sexual differentiation of hypothalamic regions during adolescence: the anteroventral periventricular nucleus (AVPV) and sexually dimorphic nucleus of the preoptic area (SDN)
The AVPV and SDN of adult rats are sexually dimorphic, with the AVPV being larger in females than in males (female-biased) and the SDN being larger in males (male- biased). The AVPV is essential for the generation of the sexually differentiated pattern of gonadotropin releasing hormone (GnRH) secretion, as it coordinates the preovulatory GnRH and luteinizing hormone (LH) surge (Petersen and Barraclough, 1989, Wiegand and Terasawa, 1982), a neuroendocrine event displayed by female rats only
Sexual differentiation of the posterodorsal medial amygdala (MePD) during adolescence
The rodent MePD evaluates chemosensory stimuli from conspecifics and integrates this information with the internal hormonal milieu, thereby coordinating the external and internal signals that regulate social behaviors. MePD volume is larger in adult male rats than in female rats, with this sex difference being more pronounced in the right hemisphere than in the left (Cooke and Woolley, 2005, Cooke et al., 2007, Morris et al., 2008). This adult sexual dimorphism is the product of two successive
Sexual differentiation of the cerebral cortex and its connectivity during adolescence
Structural sex differences in the cerebral cortex are not as visually prominent or as large in magnitude as those in the hypothalamus where the earliest investigations of sexual differentiation of the nervous system were focused. Nevertheless, there are sex differences in the cortex and in its connections. Notably, many of the sex differences emerge during puberty as the result of exposure to ovarian hormones in females.
Sexual differentiation of the locus coeruleus (LC) during adolescence
The LC is a group of midbrain neurons that are the primary source of norepinephrine in the central nervous system and therefore this cell group has a pivotal role in the regulation of mood, basal arousal, and anxiety. The adult female rat LC is larger in volume and has more neurons than the LC of the adult male rat (Guillamon et al., 1988). This sex difference arises as the result of two postnatal periods during which growth of the female LC outpaces that of the male: the first period occurs
Conclusions
It is now clear that the creation of structural sex differences during perinatal development is just the first phase of morphological sexual differentiation of the nervous system. A second phase of sexual differentiation occurs during puberty, when gonadal hormones are once again elevated, this time in both the developing male and female. This second, pubertal, phase of sexual differentiation may be a mechanism for maintaining or establishing for the first time structural and functional sexual
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