Small dense-core vesicles

Ca2+-Induced Exocytosis of Small Dense-Core Vesicles and LDCVs. 18... 

Monoaminergic neurotransmitters (dopamine, noradrenaline, adrenaline, histamine, and serotonin) are released by exocytosis of small dense-core vesicles from... 

Catecholamines are stored in several types of vesicular granules that differ in size and type of protein and peptide components. In rat and bovine adrenal medulla there are two populations of chromaffin cells with morphologically distinct vesicles that preferentially store either norepinephrine or epinephrine and that release the two catecholamines differentially in response to different stimuli. In sympathetic nerves there are large and small dense core vesicles, the latter believed to be formed by retrieval of membranes of large dense core vesicles after exocytosis. ... 

Figure 3 Schematic diagram of open-type neuroepithelial body in salamander lung. T3 pe I cells (I) have small, dense core vesicles and are surrounded by goblet cells (G). T3 pe II cells (II) have large, dense core vesicles, are in contact with the respiratory surface of the airway (A) by a single modified cilium, and are surrounded by ciliated cells (CL). Innervation is in the base (star). (From Ref 30.)...

Synaptic vesicles are the organelles in axon terminals that store neurotransmitters and release them by exocytosis. There are two types, the large dense-core vesicles, diameter about 90 nm, that contain neuropeptides, and the small synaptic vesicles, diameter about 50nm, that contain non-peptide transmitters. About ten vesicles per synapse are docked to the plasma membrane and ready for release, the readily releasable pool . Many more vesicles per synapse are stored farther away from the plasma membrane, the resting pool . When needed, the latter vesicles may be recruited into the readily releasable pool. Neuronal depolarization and activation of voltage-sensitive Ca2+... 

Figure 4.10 An electron micrograph of a terminal varicosity containing a large dense-core vesicle (LDCV), indicated by the arrow and many small synaptic vesicles (SSVs), some of which contain an electron dense core. Calibration mark 250 nM. (Figure kindly supplied by M. Fillenz)...

FIGURE18-4 Neuropeptides and conventional neurotransmitters are released from different parts of the nerve terminal. A neuromuscular junction containing both large dense-core vesicles (containing the neuropeptide SCP) and also small synaptic vesicles (containing acetylcholine) was stimulated for 30 min at 12 Hz (3.5 s every 7 s). Depletion of the small clear vesicles at the muscle face and of the peptide granules at the nonmuscle face of the nerve terminal was observed. After stimulation, there was an increase in the number of large dense-core vesicles within one vesicle diameter of the membrane. (Adapted from reference [37].)... 

The terminals of cholinergic neurons contain large numbers of small membrane-bound vesicles concentrated near the synaptic portion of the cell membrane (Figure 6-3) as well as a smaller number of large dense-cored vesicles located farther from the synaptic membrane. The large vesicles contain a high concentration of peptide cotransmitters (Table 6-1), while the smaller clear vesicles contain most of the acetylcholine. Vesicles are initially synthesized in the neuron soma and transported to the terminal. They may also be recycled several times within the terminal. 

Fora basic account of synapses in general, see the text by Threadgold 877). Synapses have been examined in a number of genera, e.g. Diphyllobothrium, Echinococcus and Hymenolepis 277, 726,936,941,943). In the plerocercoid of Diphyllobothrium dendriticum, synapses are formed between neurites in which the presynaptic neurite contains (a) both dense-core vesicles and clear vesicles or b) small clear vesicles only (Fig. 2.10). The former correspond closely to the dense-core vesicles of aminergic neurones, and have been tentatively classified as aminergic synapses (277), whilst the latter are classified as cholinergic synapses. These neurones are discussed further below. 

Local modulation through the dendritic release of DA occurs in both the SN and the VTA. Ultrastructural observations have been made with immunolocalization of the vesicular monoamine transporter-2 as marker for sites of intracellular monoamine storage within SN and VTA dopaminergic neurons identified by TH immunoreactivity (Nirenberg et al., 1996a). This study has reported that DA is stored in and may be released from dendritic small synaptic vesicles or large dense-core vesicles, while the smooth endoplasmic reticulum represents the main site for the DA storage. 

Ahnert-Hilger G, Schafer T, Spicher K, Grund C, Schultz G, Wiedenmann B (1994) Detection of G-protein heterotrimers on large dense core and small synaptic vesicles of neuroendocrine and neuronal cells. Eur J Cell Biol 65 26-38... 

In cestodes, most, perhaps all, of the neural elements are found in the ganglia of the scolex and the main nerve tracts. In these, the cell bodies are arranged peripherally around a core made up of a tangled mass of neuronal processes often referred to as neurites because it is impossible to distinguish between axons and dendrites. This mass constitutes the so-called neuropile . Like all differentiated cells in cestodes - and probably in all invertebrates - nerve cells are incapable of mitosis and hence new nerve cells must arise directly from the germinative ( = stem) cells (276). In D. dendriticum, the neuropile is composed of a dense network of unmyelinated nerve fibres with no extracellular stroma between the fibres (277). The fibres differ mainly in the content of different types of vesicles, which can be dense-core, small clear or large clear vesicles. The structure of synapses is discussed further on pp. 25—7. 

Fig. 2.10. Diphyllobothrium dendriticum types of single and shared synaptic contacts. The nerve terminals are filled with dense-core and small clear vesicles, (a) Single synapse. (b) Shared synapse, (c) Single synapse on nerve fibre with dense-core and small clear vesicles, (d) Single shared synapse on large lucent nerve with mixed vesicle content and of presumed sensory nature. (e) Shared synapse on peptidergic nerve fibre and fibre lacking special characteristics. (/) Shared synapse on glycogen-rich parenchyma cells. The postsynaptic densities (bold arrows) and the synaptic clefts (thin arrows) are well developed in all synapses. (After Gustafsson, 1984.)...

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