Development of the human cingulate cortex in the perinatal period: an experimental study

DEVELOPMENT OF THE HUMAN CINGULATE CORTEX IN THE PERINATAL PERIOD: AN EXPERIMENTAL STUDY (ABSTRACT)^*. THESIS. RIO DE JANEIRO, 2000.

LEONARDO C. DE AZEVEDO^**

The development of the cerebral cortex in humans has seldom been the subject of experimental studies, for lack of appropriate techniques.

We approached this issue by associating modern postmortem tracing with histochemistry and immunohistochemistry, applied to the cingulate cortex (CgC) of fetuses in the second half of gestation. (1) In order to identify developing callosal neurons in the CgC, we inserted DiI crystals into the bisected midsagital callosal surface of fetuses at 25-32 weeks post-ovulatory (wpo). After 4-6 months, blocks of the CgC were cut and analysed under a fluorescence microscope. (2) In order to establish the nitridergic (NO – nitric oxide positive cells) phenotype of developing neurons of 18-35 wpo fetuses, sections were reacted histochemically for diaphorase. (3) In order to follow the development of radial glial cells (RGCs) in the CgC of fetuses at 24-40 wpo, we inserted DiI and DiA crystals into the pial and ventricular surfaces, and processed adjacent blocks for vimentin and GFAP.

Our results showed that: (1) callosal cells were detected in the transient subplate (SP) with different dendritic morphologies, indicating an advanced degree of differentiation; (2) many cingulate SP neurons were positive for diaphorase, with similar morphologies as callosal cells, suggesting that some of the latter may be nitridergic; (3) pially and ventricularly inserted DiI/DiA revealed RGCs were seen to detach first from the ventricular surface, starting their transformation into astrocytes; (4) RG fibers presented a depth-correlated morphology, being smooth at the cortical plate (CP), covered with varicosities and spines in the upper SP and progressively rougher close to the cell body, suggesting that this transitory layer and other local factors might be influencing glial transformation.

We concluded that the developing cingulate cortex in the perinatal period is the site of dynamic transformations of radial glial cells and contains transient neurons at the SP that display an unexpected hodological and neurochemical complexity.

KEY WORDS: human brain, cortical development, limbic system, corpus callosum, cortical plate, subplate, nitric oxide, radialglia, astrocytes.

**Address: Rua Sorocaba, 477 / 1003, 22271-110 Rio de Janeiro RJ, Brasil. E-mail: [e-mail]

*

Desenvolvimento do córtex cerebral humano no período perinatal: um estudo experimental (Resumo). Tese de Doutorado, Instituto de Ciências Biomédicas da Universidade Federal do Rio de Janeiro / Pós-Graduação em Ciências Morfológicas (Área: Neurociências). Orientador: Roberto Lent.

Publication Dates

• Publication in this collection
  07 June 2001
• Date of issue
  June 2001