In vivo magnetic resonance imaging reveals the effect of gonadal hormones on morphological and functional brain sexual dimorphisms in adult sheep. (November 2019)

• Record Type: Journal Article
• Authors: Barrière, David André; Ella, Arsène; Adriaensen, Hans; Roselli, Charles E.; Chemineau, Philippe; Keller, Matthieu
• Is Part Of: Psychoneuroendocrinology. Volume 109(2019)
• Publication Date: 2019-11
• Subjects: Sex differences -- Sheep -- Voxel-based morphometry -- Resting state fMRI -- Gonadectomy; Psychoneuroendocrinology -- Periodicals; Endocrinology -- Periodicals; Neurology -- Periodicals; Psychiatry -- Periodicals; Neuropsychoendocrinologie -- Périodiques; 616.8
• DOI: 10.1016/j.psyneuen.2019.104387
• Languages: English
• ISSNs: 0306-4530

Abstract

Highlights: Brain sex differences can be observed by using MRI in sheep, a well-recognized model in neuroendocrinology. Adult male and female brains show important sexual dimorphisms. Gonadectomy reduces these differences, showing their dependence on adult circulating hormone levels. Abstract: Sex differences in the brain and behavior are produced by the perinatal action of testosterone, which is converted into estradiol by the enzyme aromatase in the brain. Although magnetic resonance imaging (MRI) has been widely used in humans to study these differences, the use of animal models, where hormonal status can be properly manipulated, is necessary to explore the mechanisms involved. We used sheep, a recognized model in the field of neuroendocrinology, to assess brain morphological and functional sex differences and their regulation by adult gonadal hormones. To this end, we performed voxel-based morphometry and a resting-state functional MRI approach to assess sex differences in gonadally intact animals. We demonstrated significant sex differences in gray matter concentration (GMC) at the level of the gonadotropic axis, i.e., not only within the hypothalamus and pituitary but also within the hippocampus and the amygdala of intact animals. We then performed the same analysis one month after gonadectomy and found that some of these differences were reduced, especially in the hypothalamus and amygdala. By contrast, we found few differences in the organization of the functional connectome between males and females either before or after gonadectomy. As a whole, our study identifies brain regions that are sexually dimorphic in the sheep brain at the resolution of the MRI and highlights the role of gonadal hormones in the maintenance of these differences.