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Exocytosis and nerve terminal pseudopodia
Federation Proceedings
|April 1, 1982
Summary
Reciprocal pseudopodial indentations (PSIs) form between abutted nerve terminals in the rat brain, potentially leading to action potential block in GABAergic pathways due to potassium accumulation.
Area of Science:
- Neuroscience
- Cell Biology
- Neuroanatomy
Background:
- Synaptic vesicle exocytosis alters nerve terminal membrane geometry.
- Previous studies in electric rays showed reciprocal pseudopodial indentations (PSIs) between stimulated nerve terminals.
- The necessity of direct nerve terminal abutment for PSI formation was investigated.
Purpose of the Study:
- To examine rat brain limbic system nuclei for PSI configurations.
- To investigate the role of PSIs in gamma-aminobutyric acid (GABA) afferent pathways.
- To understand the regulation of PSI generation and its impact on neuronal function.
Main Methods:
- Microscopic examination of nerve terminal configurations in rat brain limbic system nuclei.
- Analysis of synaptic connections, particularly between GABAergic afferents and smooth dendrites.
- Computational modeling of extracellular potassium (K+) accumulation at PSI tips.
Main Results:
- PSIs are abundant in the globus pallidus and substantia nigra, primarily between abutted terminals synapsing with smooth dendrites.
- These PSIs are likely formed by GABAergic afferents from the caudate-putamen.
- Calculations indicate that extracellular K+ concentrations could reach 15 mM at 150 Hz firing rates, potentially causing action potential block.
Conclusions:
- PSI formation and associated K+ accumulation may lower the safety factor for action potential conduction in GABAergic pathways.
- This phenomenon could impact inhibitory tone in the substantia nigra.
- Further research is needed to understand synaptic vesicle behavior during depolarization and its regulation of PSI generation.