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Ultrastructure of developing substantia nigra in humans
1Department of Anatomy, All India Institute of Medical Sciences, New Delhi, India.
Summary
Synaptogenesis in the human substantia nigra begins by 8 weeks gestation. This process of neural development continues past 24 weeks, with increasing synapse complexity and neuronal maturation observed.
Area of Science:
- Neuroscience
- Developmental Biology
- Electron Microscopy
Background:
- The substantia nigra is crucial for motor control, and its development is vital.
- Understanding the timeline of neuronal and synaptic maturation is key to comprehending early brain development.
Purpose of the Study:
- To investigate the early stages of neuronal and synaptic development in the human substantia nigra.
- To characterize the morphological changes during synaptogenesis from 8 to 24 weeks of gestation.
Main Methods:
- Utilized electron microscopy to examine neuronal and synaptic development.
- Analyzed tissue from 14 human embryos/foetuses aged 8-24 weeks of gestation.
Main Results:
- Immature neurons and electron-dense contacts observed at 8 weeks.
- Identifiable neurons and asymmetric synapses present by 12 weeks, with nigro-striatal and Substance P fiber involvement.
- Increased number and maturation of synapses, including appearance of symmetric synapses, by 15-16 weeks.
- Neurons exhibit mature cytological features by 24 weeks, with increased synapse number and variety.
Conclusions:
- Synaptogenesis in the human substantia nigra commences around 8 weeks gestation.
- The development of both asymmetric and symmetric synapses occurs during gestation.
- Neuronal maturation and synaptogenesis continue beyond 24 weeks of gestation.