The effects of partial and complete masculinization on the sexual differentiation of nuclei that control lordotic behavior in the male rat.
Level 5 - mechanism / opinion, no new human data
Animal laboratory experiment
PubMed 18929601 · doi:10.1016/j.bbr.2008.09.017
What was done
Researchers evaluated the morphological differentiation of brain structures controlling female sexual receptivity (lordosis) across four groups of rats: males castrated neonatally and injected with vehicle oil (GxM+oil), males castrated neonatally and treated with androstenedione (GxM+AND), sham-operated control males (CM), and control females (CF). In adulthood, the animals were tested for lordotic behavior, and the volume or neuronal counts were measured in facilitatory structures (ventromedial nucleus of the hypothalamus [VMN], ventrolateral VMN [VMNvl]) and inhibitory structures (intermediate region of the lateral septum [LSi], accessory olfactory bulb [AOB]).
What was found
The abstract reports no numerical values, sample sizes, or test statistics. Qualitatively, neonatal testosterone presence was associated with morphological masculinization of the VMN, VMNvl, LSi, and AOB, which corresponded with the behavioral inhibition of lordosis in adult male rats.
Why it matters
This study outlines the structural neuroanatomy underlying sexual differentiation of sexual reflexes in rodents, suggesting that neonatal androgen-driven changes in both facilitatory and inhibitory brain nuclei act together to suppress female-typical sexual behavior in males.
Limits
Findings are limited to an animal model and cannot be directly applied to human sexual behavior or neuroanatomy. The abstract does not provide specific sample sizes, effect sizes, variance estimates, or statistical significance metrics for the morphological or behavioral changes.
Cited by
- supports Male rats castrated on the day of birth and treated with estrogen and progesterone in adulthood display female-typical lordosis posture when mounted.