Proinflammatory Peptides in Sensory Nerves of the Airways
Sami I. Said in Proinflammatory and Antiinflammatory Peptides, 2020
The airways are innervated by three sets of anatomically distinct pathways of sympathetic, parasympathetic, and sensory nerves. All three pathways contain neuropeptides, sometimes coexisting with nonpeptide transmitters, such as acetylcholine, norepinephrine, and nitric oxide. The postganglionic cell bodies of the sympathetic nerves are located in the superior cervical and stellate ganglia, whereas the post-ganglionic cell bodies of the parasympathetic nerves are located in small, local intrinsic ganglia embedded in the walls of the airways (10). Nerve degeneration studies and retrograde tracing studies show that the cell bodies of the tracheal sensory nerves are located in the jugular and nodose ganglion, while the upper thoracic dorsal root ganglia also contribute sensory fibers to the lungs (11–14). It has also been suggested recently that local interneurons or sensory neurons may exist within the intrinsic airway ganglia (15), similar to the intrinsic sensory neurons in enteric ganglia (16). Most sensory nerve fibers in the airways are long, branching, unmyelinated fibers with many varicosities or beads approximately 1–2 μm in diameter, connected by thinner intervaricose portions approximately 0.1–0.5 μm in diameter, thus making the entire nerve fiber within the resolution of the light microscope. Synaptic vesicles within the varicosities contain various transmitters. Some sensory nerve fibers, including those for stretch receptors, are myelinated (17).
Homeostasis of Dopamine
Nira Ben-Jonathan in Dopamine, 2020
Secretory vesicles of neuroendocrine cells (exemplified by adrenal medullary chromaffin granules) differ from synaptic vesicles of the CNS in size, morphology, content, biogenesis, and speed of release [57]. Secretory vesicles are larger; have a diameter of 270 nm; contain biogenic amines, ions, peptides, and proteins; are derived from the Golgi apparatus; and are retrieved after exocytosis, but they do not directly recycle. The condensed proteins within the secretory vesicles are visualized in electron micrographs as a solid core and have, therefore, been identified as dense core secretory granules or vesicles. On the other hand, synaptic vesicles are much smaller, have a diameter of 40–60 nm, contain only neurotransmitters, and appear as clear vesicles in electron micrographs. Synaptic vesicles are derived from the endosome, the major sorting compartment within the cell. Synaptic vesicles also release their content very rapidly, and they completely recycle by endocytosis after emptying. Given that synaptic vesicles are not formed at the Golgi complex, they do not contain newly synthesized proteins. Instead, they take up the neurotransmitters from the cytoplasm, using the VMAT intracellular transporters.
Histology and Pathology of the Human Neuromuscular Junction with a Description of the Clinical Features of the Myasthenic Syndromes
Marc H. De Baets, Hans J.G.H. Oosterhuis in Myasthenia Gravis, 2019
Synaptic vesicles are formed in the neuron cell body and transported by fast axonal transport to the the motor nerve terminal.21,22 Once arrived in the terminal they need to be translocated to the presynaptic membrane (Figure 5). Proteins in the vesicle wall assist in translocation and in fusion of the vesicles with the plasma membrane. Synapsin, a family of four, homologous, synaptic vesicle specific proteins helps in moving the vesicles along the cytoskeletal system in the nerve terminal towards the “active zones”, the docking areas of the presynaptic membrane. In frogs, the vesicles are accumulated near these active zones but this is not obvious on transmission electronmicrographs of human nerve terminals as the active zones are not easily identified. Close to the active zones, the vesicles become attached to an actin network which in its turn is linked to the plasma membrane by fodrin (brain spectrin). Synaptophysin, the most abundant of the vesicle wall proteins, may participate in forming fusion pores for synaptic vesicle exocytosis (see for review of vesicle wall and active zone proteins references 17 and 23 and Chapter 3).
The neurosciences at the Max Planck Institute for Biophysical Chemistry in Göttingen
Published in Journal of the History of the Neurosciences, 2023
Heinz Wässle, Sascha Topp
From 1959, Victor Whittaker carried out important and ground-breaking work on the function of the synaptic vesicles and on the role of acetylcholine as a neurotransmitter (Zimmermann and Fonnum 2016). Two technical innovations made this success possible: the availability of adequate centrifuges and introduction of electron microscopy (Zimmermann 2018). Whittaker managed to fractionate the brain tissue of mammals and to enrich different elements through centrifugation (Whittaker 1959). One of these fractions contained large quantities of organelles filled with synaptic vesicles. Under the electron microscope, it was shown that these were pinched off nerve terminals, and Whittaker named them synaptosomes (Gray and Whittaker 1962). The team was able to enrich vesicles from synaptosomes and to find that the neurotransmitter acetylcholine is stored in the vesicles.
Datumetine exposure alters hippocampal neurotransmitters system in C57BL/6 mice
Published in Drug and Chemical Toxicology, 2022
Azeez Olakunle Ishola, Aminu Imam, Moyosore Salihu Ajao
Electron microscopy studies on the synapse revealed that datumetine exposed animals showed a reduction in the number of viable synapses with 1.0 mg/kg Datumetine animals showing the greatest reduction compared to controls. It is on record that overactivation of NMDAR leads to synaptic loss (Talantova et al.2013, Zhou et al.2013, Lewerenz and Maher 2015). This observation may be due to the persistent interaction of datumetine with NMDAR (Ishola et al.2020). The postsynaptic density was thicker in datumetine exposed animals with a great reduction in presynaptic vesicles. Chemical neurotransmission is through the release of synaptic vesicles (Trkanjec and Demarin 2001, Ikeda and Bekkers 2009) which are tightly regulated by re-uptake back to the presynaptic neurons (Piedras-Renteria et al.2004, Dickman et al.2012, Davis and Muller 2015). Datumetine greatly reducing the number of synaptic vesicles showed that either reuptake of the vesicles is altered, or rate of production is not balanced with the rate of release (Wang et al.2016, Li and Kavalali 2017). Another possible explanation may be that NMDAR binding with datumetine increases the affinity of presynaptic NMDAR for glutamate thereby increasing the release of neurotransmitters (Reimer et al.1998, Takamori 2016).
The preventive and therapeutic effect of repetitive transcranial magnetic stimulation on radiation-induced brain injury in mice
Published in International Journal of Radiation Biology, 2022
Li-Yuan Liu, Tong-Zhou Qin, Ling Guo, Huang Rong-Rong, Yun-Tao Jing, Pan-Pan Lai, Yi-zhe Xue, Gui-Rong Ding
After blood was flushed with 0.9% sodium chloride, the brains were harvested, and the hippocampus was isolated. Small pieces of the hippocampus were rapidly placed into glutaraldehyde, fixed for at least 1 h at room temperature and then postfixed in osmium tetroxide, embedded in agar, dehydrated in graded concentrations of ethanol and propylene oxide, and embedded in Spurr's plastic. Semithin sections were cut from the blocks with a glass knife, and then blocks were selected to prepare thin sections. Thin sections (50 nm) were cut with diamond knives, placed on copper grids, impregnated with uranyl acetate and lead citrate, and visualized under a microscope. Tissues from 3 animals for each group were analyzed, the size of synapses and the number of synaptic vesicles were measured.
Related Knowledge Centers
- Action Potential
- Axon
- Axon Terminal
- Chemical Synapse
- Vesicle
- Neurotransmitter
- Exocytosis
- Neuron
- Voltage-Gated Calcium Channel
- Cell