Morphological sex differences and laterality in the prepubertal medial amygdala

The medial amygdala (MeA) is crucial in the expression of sex‐specific social behaviors. In adult rats the regional volume of the MeA posterodorsal subnucleus (MeApd) is ≈50% larger in males than in females. The MeApd is also sexually dimorphic in prepubertal rats. We have recently shown that the le...

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Published in:	Journal of comparative neurology (1911) Vol. 501; no. 6; pp. 904 - 915
Main Authors:	Cooke, Bradley M., Stokas, Michael R., Woolley, Catherine S.
Format:	Journal Article
Language:	English
Published:	Hoboken Wiley Subscription Services, Inc., A Wiley Company 20-04-2007
Subjects:	Amygdala - cytology Amygdala - physiology Animals axon Cell Count dendrite Dendrites - physiology electron microscopy Female Functional Laterality - physiology glia Male Neurons - cytology Neurons - physiology Organ Size Rats Rats, Sprague-Dawley Sex Characteristics Sexual Maturation - physiology stereology synapse
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Summary:	The medial amygdala (MeA) is crucial in the expression of sex‐specific social behaviors. In adult rats the regional volume of the MeA posterodorsal subnucleus (MeApd) is ≈50% larger in males than in females. The MeApd is also sexually dimorphic in prepubertal rats. We have recently shown that the left MeApd is significantly larger in prepubertal males than females. In contrast with volumetric sex differences elsewhere in the brain, however, we found no sex difference in the number of left MeApd neurons. In the present study we investigated the cellular bases of the sex difference in MeApd regional volume by quantifying the volume occupied by dendrites, axons, synapses, or glia, and by measuring MeApd dendritic morphology in 26–29‐day‐old male and female rats. We find that the volume occupied by dendritic shafts and glia completely accounts for the sex difference in left MeApd regional volume. Dendritic length measurements in the left hemisphere confirm that males have greater overall dendritic length, which is due to greater branching rather than to longer dendrite segments. In the right hemisphere the pattern of sex differences was different: Males have more MeApd neurons than females, whereas the dendritic morphology of individual neurons is not sexually dimorphic. These results highlight the importance of evaluating laterality in the MeA and suggest that the left and right MeA could play different roles in neuroendocrine regulation and sexually dimorphic social behaviors. J. Comp. Neurol. 501:904–915, 2007. © 2007 Wiley‐Liss, Inc.
Bibliography:	istex:33832501708151BAA0B123A949C8D452ABDB0237 ark:/67375/WNG-X0LFRL9R-V National Institute on Neurological Disorders and Stroke - No. R01 NS37324 National Center for Research Resources - No. C06 RR015497 ArticleID:CNE21281 W.M. Keck Foundation - No. MH073335 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0021-9967 1096-9861
DOI:	10.1002/cne.21281