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Nerve cell rearrangement in neocortical layers of MAM treated foetal mice
S Ciaroni1, T Cecchini, P Ambrogini
1Istituto Scienze Morfologiche Università-Urbino.
Abstract:
In this study we examined the changes in cortical layers when Methylazoxymethanol-acetate (MAM) was injected on 13th, 15th and 17th day of gestation (MAM13, MAM15, MAM17). Prenatal MAM administration prevents neuron precursor proliferation; the subsequent cell number decrease is followed by an increase in size of surviving cells. When MAM was injected on 13th or 15th day of gestation the significant decrease in cell density, in II and III zone (MAM13) and in the upper layers (MAM15), was compensated by a proportional increase in cell size and synaptic density. When MAM was injected on 17th embryonal day it did not cause a significant change in the neuron density and soma size was not altered while the distribution of cell size among layers showed significant differences with respect to the controls. Our findings of some area and synaptic density show that the cell surface increase is proportional to the decrease in cell number and that in the surviving cells there is a rearrangement in synaptic connections that compensate for the cellular density decrease.
Insights
Prenatal exposure to Methylazoxymethanol-acetate (MAM) alters cortical layer development. Surviving neurons increase in size and synaptic density, compensating for reduced cell numbers in developing brains.
Area of Science:
- Neuroscience
- Developmental Biology
- Toxicology
Background:
- Prenatal exposure to toxins can disrupt normal brain development.
- Methylazoxymethanol-acetate (MAM) is a known neuroteratogen affecting neuron proliferation.
Purpose of the Study:
- To investigate the effects of prenatal MAM administration on cortical layer development at different gestational days.
- To analyze changes in neuronal density, size, and synaptic organization in response to MAM exposure.
Main Methods:
- Pregnant rats were administered MAM on embryonic days 13, 15, or 17.
- Cortical layers were analyzed for cell density, soma size, and synaptic density.
- Comparisons were made between MAM-exposed groups and control groups.
Main Results:
- MAM administration on gestation days 13 and 15 led to decreased cell density, compensated by increased cell size and synaptic density in specific cortical layers.
- MAM administration on gestation day 17 did not significantly alter neuron density or soma size, but affected cell size distribution.
- Findings suggest a compensatory mechanism involving cell enlargement and synaptic rearrangement in surviving neurons.
Conclusions:
- Prenatal MAM exposure differentially impacts cortical development depending on the timing of administration.
- Surviving neurons exhibit plasticity, increasing in size and modifying synaptic connections to compensate for reduced cell numbers.
- These findings provide insights into the long-term consequences of developmental neurotoxicity on brain structure and function.