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Vasoactive intestinal polypeptide in brain: localization in and release from isolated nerve terminals
Summary
Vasoactive intestinal polypeptide (VIP) is concentrated in rat brain nerve endings. Its release from these synaptosomes is calcium-dependent, suggesting VIP acts as a neurotransmitter or modulator.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Vasoactive intestinal polypeptide (VIP) is a peptide found in various tissues, including the brain.
- Its precise role in synaptic function has been under investigation.
Purpose of the Study:
- To investigate the localization and release of VIP in rat brain synaptosomes.
- To explore the potential role of VIP as a neurotransmitter or neuromodulator.
Main Methods:
- Synaptosomal preparations from rat cerebral cortex, hypothalamus, and striatum were analyzed for VIP content.
- Peptide purification and analysis of synaptosomal fractions were performed.
- VIP release from synaptosomal pellets was induced and measured under varying conditions, including K+ concentration and Ca2+ dependency.
Main Results:
- VIP was found in higher concentrations in synaptosomal preparations compared to whole brain tissues.
- VIP content and specific activity increased with synaptosomal fraction purification, correlating with known synaptosomal markers like dopamine and norepinephrine.
- Potassium-stimulated release of VIP from synaptosomes was observed, and this release was dependent on the presence of calcium ions.
Conclusions:
- The findings strongly suggest that VIP is localized within nerve endings (synaptosomes) in specific rat brain regions.
- The calcium-dependent release of VIP from synaptosomes indicates its potential function as a neurotransmitter or modulator in synaptic transmission.
- VIP's presence and release characteristics support its role in regulating neuronal activity.