Dendritic spines of the medial amygdala: plasticity, density, shape, and subcellular modulation by sex steroids
Alberto A. Rasia-Filho1,2, Francine Dalpian1, Itiana C. Menezes2, Janaína Brusco3,4, Jorge E. Moreira3,4 and Rochelle S. Cohen5
1Department of Basic Sciences/Physiology, Graduation Program in Pathology, Federal University of Health Sciences of Porto Alegre, Brazil, 2Graduation Program in Neurosciences, Federal University of Rio Grande do Sul, Brazil, 3Department of Cell, Molecular Biology and Biopathogens, Ribeirão Preto School of Medicine, University of São Paulo, Brazil, 4Department of Neuroscience and Behavior, Ribeirão Preto School of Medicine, University of São Paulo, SP, Brazil and 5Department of Anatomy and Cell Biology, University of Illinois at Chicago, USA.
Offprint requests to: Prof. Alberto A. Rasia-Filho, UFCSPA/Physiology, R. Sarmento Leite 245, Porto Alegre 90170-050 RS, Brazil. e-mail: rasiafilho@pq.cnpq.br
Summary. The medial nucleus of the amygdala (MeA) is a complex component of the “extended amygdala” in rats. Its posterodorsal subnucleus (MePD) has a remarkable expression of gonadal hormone receptors, is sexually dimorphic or affected by sex steroids, and modulates various social behaviors. Dendritic spines show remarkable changes relevant for synaptic strength and plasticity. Adult males have more spines than females, the density of dendritic spines changes in the course of hours to a few days and is lower in proestrous and estrous phases of the ovarian cycle, or is affected by both sex steroid withdrawal and hormonal replacement therapy in the MePD. Males also have more thin spines than mushroom-like or stubby/wide ones. The presence of dendritic fillopodia and axonal protusions in the MePD neuropil of adult animals reinforces the evidence for local plasticity. Estrogen affects synaptic and cellular growth and neuroprotection in the MeA by regulating the activity of the cyclic AMP response element-binding protein (CREB)-related gene products, brain-derived neurotrophic factor (BDNF), the anti-apoptotic protein B-cell lymphoma-2 (Bcl-2) and the activity-regulated cytoskeleton-related protein (Arc). These effects on signal transduction cascades can also lead to local protein synthesis and/or rearrangement of the cytoskeleton and subsequent numerical/morphological alterations in dendritic spines. Various working hypotheses are raised from these experimental data and reveal the MePD as a relevant region to study the effects of sex steroids in the rat brain. Histol Histopathol 27, 985-1011 (2012)
Key words: Amygdala/cytology, CREB, Gonadal hormones, Neural pathways/axonal network, Sexual dimorphism
DOI: 10.14670/HH-27.985