Question

What are some of the differences between small, clear vesicle and large dense-core vesicles (content, synthesis, activity characteristics associated with release)?

Answer 1

Small core vesicles are the synaptic vesicles whose middle portion appears clear in the electron micrograph. These are about 40 to 60 nm in diameter and small molecule neurotransmitters like acetylcholine or amino acids neurotransmitters are packed in such type of vesicles.

Large core vesicles are the synaptic vesicles whose middle portion appears quite dense in the electron micrograph hence these are called large dense vesicles. They are about 90–250 nm in diameter. Larger molecules like neuropeptides are packed in these vesicles. These vesicles are apparently large as other molecules like proteases and other peptide chains that have been cleaved from the active neurotransmitter are also present along with the main neurotransmitter.

As far as packing is considered large dense core vesicles are stored in cages in bouton away from the synapse in comparison to small core vesicles which means that the release of neuropeptide neurotransmitters generally has a longer delay than the release of small molecule neurotransmitters.