Differential long‐term neurotoxicity of HIV‐1 proteins in the rat hippocampal formation: A design‐based stereological study

Amaral

et al. 2012

111

Abnormal development of the amygdala has been linked to several neurodevelopmental disorders, including schizophrenia and autism. However, the postnatal development of the amygdala is not easily explored at the cellular level in humans. Here we performed a stereological analysis of the macaque monkey amygdala in order to characterize the cellular changes underlying its normal structural development in primates. The lateral, basal, and accessory basal nuclei exhibited the same developmental pattern, with a large increase in volume between birth and 3 months of age, followed by slower growth continuing beyond 1 year of age. In contrast, the medial nucleus was near adult size at birth. At birth, the volume of the central nucleus was half of the adult value; this nucleus exhibited significant growth even after 1 year of age. Neither neuronal soma size, nor neuron or astrocyte numbers changed during postnatal development. In contrast, oligodendrocyte numbers increased substantially, in parallel with an increase in amygdala volume, after 3 months of age. At birth, the paralaminar nucleus contained a large pool of immature neurons that gradually developed into mature neurons, leading to a late increase in the volume of this nucleus. Our findings revealed that distinct amygdala nuclei exhibit different developmental profiles and that the amygdala is not fully mature for some time postnatally. We identified different periods during which pathogenic factors might lead to the abnormal development of distinct amygdala circuits, which may contribute to different human neurodevelopmental disorders associated with alterations of amygdala structure and functions.

Section: Methodsmentioning

confidence: 99%

Postnatal development of the amygdala: A stereological study in macaque monkeys

Amaral

et al. 2012

111

“…3). We refer the reader to the original publications by (Palackal et al, 1993; Grady et al, 2003; Hamidi et al, 2004; Fitting et al, 2008) for detailed descriptions. Neurons are heavily stained with a large and single nucleolus (Fig.…”

Section: Methodsmentioning

confidence: 99%

Stereological analysis of the rat and monkey amygdala

Amaral

et al. 2011

121

156

The amygdala is part of a neural network that contributes to the regulation of emotional behaviors. Rodents, especially rats, are used extensively as model organisms to decipher the functions of specific amygdala nuclei, in particular in relation to fear and emotional learning. Analysis of the role of the nonhuman primate amygdala in these functions has lagged work in the rodent but provides evidence for conservation of basic functions across species. Here we provide quantitative information regarding the morphological characteristics of the main amygdala nuclei in rats and monkeys, including neuron and glial cell numbers, neuronal soma size, and individual nuclei volumes. The volumes of the lateral, basal, and accessory basal nuclei were, respectively, 32, 39, and 39 times larger in monkeys than in rats. In contrast, the central and medial nuclei were only 8 and 4 times larger in monkeys than in rats. The numbers of neurons in the lateral, basal, and accessory basal nuclei were 14, 11, and 16 times greater in monkeys than in rats, whereas the numbers of neurons in the central and medial nuclei were only 2.3 and 1.5 times greater in monkeys than in rats. Neuron density was between 2.4 and 3.7 times lower in monkeys than in rats, whereas glial density was only between 1.1 and 1.7 times lower in monkeys than in rats. We compare our data in rats and monkeys with those previously published in humans and discuss the theoretical and functional implications that derive from our quantitative structural findings.

“…2). We refer the reader to original publications (Fitting et al, 2008;Grady et al, 2003;Hamidi et al, 2004;Palackal et al, 1993) for detailed descriptions. Briefly, neurons are darkly stained and make up a single large nucleolus.…”

Section: Stereological Analysesmentioning

confidence: 99%

Postnatal development of the amygdala: A stereological study in rats

2012

The amygdala is the central component of a functional brain system regulating fear and emotional behaviors. Studies of the ontogeny of fear behaviors reveal the emergence of distinct fear responses at different postnatal ages. Here, we performed a stereological analysis of the rat amygdala to characterize the cellular changes underlying its normal structural development. Distinct amygdala nuclei exhibited different patterns of postnatal development, which were largely similar to those we have previously shown in monkeys. The combined volume of the lateral, basal, and accessory basal nuclei increased by 113% from 1 to 3 weeks of age and by an additional 33% by 7 months of age. The volume of the central nucleus increased only 37% from 1 to 2 weeks of age and 38% from 2 weeks to 7 months. At 1 week of age, the medial nucleus was 77% of the 7-monthold's volume and exhibited a constant, marginal increase until 7 months. Neuron number did not differ in the amygdala from 1 week to 7 months of age. In contrast, astrocyte number decreased from 3 weeks to 2 months of age in the whole amygdala. Oligodendrocyte number increased in all amygdala nuclei from 3 weeks to 7 months of age. Our findings revealed that distinct amygdala nuclei exhibit different developmental profiles and that the rat amygdala is not fully mature for an extended period postnatally. We identified different periods of postnatal development of distinct amygdala nuclei and cellular components, which are concomitant with the ontogeny of different fear and emotional behaviors.