The pyramidal neuron in cerebral cortex following prenatal X-irradiation
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X-irradiation during pregnancy caused abnormal brain tissue (ectopic cortex) in rat offspring. Despite abnormal location, these ectopic cortical neurons showed normal synapse structures, suggesting potential functionality.
Area of Science:
- Neuroscience
- Developmental Biology
- Radiology
Background:
- Prenatal exposure to radiation can impact brain development.
- Ectopic neural tissue formation is a potential consequence of developmental disruption.
- Understanding the cellular and synaptic integrity of ectopic brain regions is crucial.
Purpose of the Study:
- To investigate the structural and synaptic characteristics of ectopic cortex in rats exposed to X-irradiation in utero.
- To compare dendritic spine density and synapse morphology in ectopic versus normally located cortical neurons.
Main Methods:
- Pregnant rats were exposed to 125 R whole body X-irradiation on gestational day 15.
- Offspring were examined at postnatal weeks and months using light microscopy (Golgi stain) and electron microscopy.
- Dendritic spine counts and synapse morphology were analyzed in pyramidal neurons of both ectopic and normally located cortex.
Main Results:
- All irradiated rats developed ectopic cortex in the forebrain.
- Ectopic pyramidal neurons exhibited sparser dendritic spines compared to normally located neurons.
- Electron microscopy revealed morphologically normal axodendritic and axosomatic synapses in the ectopic cortex.
Conclusions:
- Prenatal X-irradiation leads to the formation of ectopic cortex in rat offspring.
- Despite altered dendritic spine density, the ectopic cortex contains structurally normal synapses.
- The presence of functional synapses suggests that ectopic cortical tissue may retain functional capabilities.
Abstract:
Pregnant rats were subjected to whole body X-irradiation amounting to 125 R, on gestational day 15. Cortical pyramidal neurons were examined in irradiated and control offspring at 4 weeks and 4 to 6 months postnatally. All gestationally irradiated rats developed ectopic cortex located below the corpus callosum adjacent to the caudate nucleus in the forebrain. With the rapid Golgi stain, counts were made of dendritic spines on the apical dendrites of layer 5 pyramidal cells in the normally-located cortex and compared with similar neurons in the ectopias. Dendritic spines were present on all pyramidal cells but spines were more sparse on ectopic pyramidal cells. Electron microscopic examination of ectopic and layered cortex in irradiated rats showed axodendritic synapses on the spines and shafts of the dendrites and axosomatic synapses, all of which were indistinguishable morphologically from synapses in control cortex. As a result of the observations made with the light and electron microscopes, it is concluded that the ectopic cortex may contain functional cells in spite of the abnormal location of the tissue.