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Insights
Male and female rats show distinct cerebral cortex development patterns. Hormonal influences, particularly estrogen, play a role in these sex-based differences in cortical thickness and neuron distribution.
Area of Science:
- Neuroscience
- Developmental Biology
- Comparative Anatomy
Background:
- Cerebral cortex development exhibits sex-specific patterns in early postnatal life.
- Hormonal factors, including estrogen, are implicated in brain development and sexual dimorphism.
Purpose of the Study:
- To investigate sex differences in the developmental trajectories of cerebral cortical thickness in Long-Evans rats.
- To explore the role of gonadal hormones in establishing these sex-based cortical asymmetries.
Main Methods:
- Longitudinal analysis of cerebral cortical thickness in male and female rats during the first postnatal month.
- Assessment of cortical thickness following neonatal gonadectomy (ovariectomy in females, castration in males).
Main Results:
- Males exhibit uniform cortical development rates, with the right cortex thicker than the left. Females show variable development, with the left cortex typically thicker.
- Estrogen receptors are present at birth and diminish by one month; their concentration shows lateralization.
- Neonatal ovariectomy in females reverses the typical left-sided cortical thickness advantage, mimicking the male pattern.
Conclusions:
- Early postnatal cerebral cortex development is sexually dimorphic in rats, with distinct patterns of thickness and lateralization.
- Gonadal hormones, particularly estrogen, significantly influence the establishment of these sex-specific cortical asymmetries.
Abstract:
In the first postnatal month, the thickness of the cerebral cortex has different patterns of development in the male and female Long-Evans rat. All areas of the male cortex appear to develop at similar rates, very rapidly for the first 10 days, then more gradually reaching a peak somewhere between 30 and 40 days of age before beginning to decrease in thickness. The same is not true for the female; for example, at birth her medial frontal cortex is further developed than her lateral posterior parietal cortex and the rate of growth in the first weeks varies immensely. The male right cortex is thicker than the left from birth to 904 days of age, but the differences become less significant with age. The female cortex is thicker on the left side in the majority of the cases, from 7 to 400 days of age, but the differences are not in general statistically significant. Estrogen receptors are found in both male and female rat cerebral cortices at birth and apparently disappear after one month. In the male the greatest concentration of receptors is in the left cortex, and in the female, in the right. The number of neurons and glia per unit area is greater in the right cortex (area 39) in the male; and in the female, in the left cortex. Ninety days after ovariectomy at birth, the female right cortex is thicker than her left, establishing a pattern similar to that of the male. In the male gonadectomized at birth, the left cortex is thicker 90 days later in the frontal and somatosensory regions but not in the occipital or posterior region.(ABSTRACT TRUNCATED AT 250 WORDS)
