RESUMO
The human cortical amygdaloid nucleus (CoA) receives exteroceptive sensory stimuli, modulates the functions coded by the intrinsic amygdaloid circuit, and constitutes the beginning of the limbic lobe continuum with direct and indirect connections toward subcortical, allocortical, and higher order neocortical areas. To provide basic data on the human CoA, we characterized and classified the neurons using the thionin and the "single-section" Golgi method adapted for postmortem brain tissue and light microscopy. We found 10 different types of neurons named according to the morphological features of the cell body, dendritic branches, and spine distribution. Most cells are multipolar spiny neurons with two or more primary dendrites, including pyramidal-like ones. Three-dimensional reconstructions evidenced the types and diversity of the dendritic spines in each neuron. The unlike density of spines along dendritic branches, from proximal to distal ones, indicate that the synaptic processing and plasticity can be different in each CoA neuron. Our study provides novel data on the neuronal composition of the human CoA indicating that the variety of cells in this region can have phylogenetic, ontogenetic, morphological, and likely functional implications for the integrated human brain function. This can reflect both a more complex subcortical synaptic processing of sensory and emotional information and an adaptation for species-specific social behavior display.
Assuntos
Complexo Nuclear Corticomedial/citologia , Neurônios/fisiologia , Adulto , Idoso , Dendritos/ultraestrutura , Espinhas Dendríticas/ultraestrutura , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Pessoa de Meia-Idade , Plasticidade Neuronal/fisiologia , Células Piramidais/fisiologia , Células Piramidais/ultraestrutura , Olfato/fisiologia , Sinapses/fisiologiaRESUMO
The posterodorsal medial amygdala (MePD) is a sexually dimorphic area and plays a central role in the social behavior network of rats. Dendritic spines modulate synaptic processing and plasticity. Here, we compared the number and structure of dendritic spines in the MePD of prepubertal males and females and postpubertal males with and without sexual experience. Spines were classified and measured after three-dimensional image reconstruction using DiI fluorescent labeling and confocal microscopy. Significantly differences are as follows: (a) Prepubertal males have more proximal spines, stubby/wide spines with long length and large head diameter and thin and mushroom spines with wide neck and head diameters than prepubertal females, whereas (b) prepubertal females have more mushroom spines with long neck length than age-matched males. (c) In males, the number of thin spines reduces after puberty and, compared to sexually experienced counterparts, (d) naive males have short stubby/wide spines as well as mushroom spines with reduced neck diameter. In addition, (e) sexually experienced males have an increase in the number of mushroom spines, the length of stubby/wide spines, the head diameter of thin and stubby/wide spines and the neck diameter of thin and mushroom spines. These data indicate that a sexual dimorphism in the MePD dendritic spines is evident before adulthood and a spine-specific remodeling of number and shape can be brought about by both puberty and sexual experience. These fine-tuned ontogenetic, hormonally and experience-dependent changes in the MePD are relevant for plastic synaptic processing and the reproductive behavior of adult rats.
Assuntos
Complexo Nuclear Corticomedial/citologia , Espinhas Dendríticas/ultraestrutura , Plasticidade Neuronal/fisiologia , Caracteres Sexuais , Comportamento Sexual Animal/fisiologia , Maturidade Sexual/fisiologia , Fatores Etários , Animais , Feminino , Masculino , Ratos , Ratos WistarRESUMO
Oxytocin has central actions that modulate synaptic plasticity and the occurrence of social behavior in rodents. The posterodorsal medial amygdala (MePD) composes a sexually dimorphic neural circuit for the display of male sexual behavior. Local dendritic spines are notably plastic and affected by context-dependent social stimuli. Here, we examined the effects of the selective deletion of the OT gene (OTKO) in the number and shape of Golgi-impregnated dendritic spines in the MePD of näive and sexually experienced (SexExp) male mice (n=6 each group). Compared to the control wild-type mice (WT), OTKO näive mice did not differ in the density of dendritic spines, but there was a significant and more intense reduction in the number of spines in the WT/SexExp (â¼40%) than in the OTKO/SexExp (â¼25%). This structural change had a spine-specific feature. That is, sexual experience induced a decrease in the number of thin (â¼50%) and mushroom-like spines (â¼35%) at the same time that increased (â¼30%) the number of stubby/wide spines. In addition, the OTKO/SexExp animals have more thin and mushroom spines than the WT/SexExp ones (â¼25% and 55%, respectively; p <0.01 in all cases). In conjunction, these novel data indicate that OT participates in the spine remodeling, synaptic refinement, and social stimuli-dependent plasticity in the MePD of male mice.
Assuntos
Complexo Nuclear Corticomedial/fisiologia , Espinhas Dendríticas/fisiologia , Ocitocina/fisiologia , Comportamento Sexual , Animais , Complexo Nuclear Corticomedial/citologia , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Ocitocina/genéticaRESUMO
Aromatase, which converts testosterone in estradiol, is involved in the generation of brain sex dimorphisms. Here we used the "four core genotypes" mouse model, in which the effect of gonadal sex and sex chromosome complement is dissociated, to determine if sex chromosomes influence the expression of brain aromatase. The brain of 16 days old XY mouse embryos showed higher aromatase expression in the stria terminalis and the anterior amygdaloid area than the brain of XX embryos, independent of gonadal sex. Furthermore, estradiol or dihydrotestosterone increased aromatase expression in cultures of anterior amygdala neurons derived from XX embryos, but not in those derived from XY embryos. This effect was also independent of gonadal sex. The expression of other steroidogenic molecules, estrogen receptor-α and androgen receptor was not influenced by sex chromosomes. In conclusion, sex chromosomes determine sex dimorphisms in aromatase expression and regulation in the developing mouse brain.