Quick Facts
Dense-core vesicles are membrane-bound structures behind a presynaptic membrane, containing neuropeptides.
Structure
Besides typical synaptic vesicles, many axons contain larger vesicles (about 100 nm in diameter) called secretory vesicles. When viewed with the electron microscope, these vesicles appear dark as they contain a soluble protein. Hence, they are referred to as “dense-core vesicles”.
Function
Chemically, neurotransmitters are either amino acids, amines, or peptides. Amine and amino acid neurotransmitters are stored in synaptic vesicles, whereas peptide neurotransmitters are found in dense-core vesicles.
Secretory granules that release peptide neurotransmitters require a much greater influx of Ca2+ ions (and so a high frequency of action potentials) and often the release is away from the active zones (Bear, Connors and Paradiso, 2007).
References
Bear, M. F., Connors, B. W. and Paradiso, M. A. (2007) Neuroscience. Lippincott Williams & Wilkins.
