Differential effect of alpha-latrotoxin on exocytosis from small synaptic vesicles and from large dense-core vesicles containing calcitonin gene-related peptide at the frog neuromuscular junction.

Abstract

The regulatory peptide called calcitonin gene-related peptide (CGRP) was detected by immunofluorescence in frog motor neurons and motor nerve terminals. In motor nerve terminals, CGRP-like immunoreactivity was found to be segregated within large dense-core vesicles. To determine whether exocytosis from acetylcholine-containing small synaptic vesicles and from CGRP-containing large dense-core vesicles can be independently stimulated, nerve-muscle preparations were exposed to alpha-latrotoxin. This toxin induced complete depletion of acetylcholine-containing small synaptic vesicles but did not induce a parallel depletion of CGRP-like immunoreactivity and of large dense-core vesicles. These effects were independent of the presence of extracellular Ca2+ and occurred both at room temperature and at low temperature (1-3 degrees C). These findings suggest that exocytosis from the two vesicle populations is mediated by distinct biochemical mechanisms, which might be differentially regulated by physiological stimuli.

From the Golgi–Cajal mapping to the transmitter-based characterization of the neuronal networks leading to two modes of brain communication: Wiring and volume transmission

“…After 1986, the ultrastructural analysis in several studies strengthened the evidence that large dense core vesicles rich in neuropeptides were preferentially associated with nonsynaptic membranes (Matteoli et al, 1988;Sossin et al, 1989;Thureson-Klein and Klein, 1990;Barinaga, 1993;see Koob et al, 1990). Thus, the release of peptides commonly occurs extrasynaptically (Golding, 1994).…”

Ryanodine‐ and CaMKII‐dependent release of endogenous CGRP induces an increase in acetylcholine quantal size in neuromuscular junctions of mice

“…Of these, CGRP is of special interest because this 37‐amino acid neuropeptide has been found in large dense‐core vesicles (LDCVs) in mammalian motor nerve terminals (Csillik et al., 1993; Matteoli et al., 1988) and is reported to be released as a co‐transmitter in response to sustained depolarization or intense nerve stimulation (Sakaguchi, Inaishi, Kashihara, & Kuno, 1991; Sala, Andreose, Fumagalli, & Lømo, 1995; Uchida et al., 1990) providing the wide spectrum of acute and neurotrophic influences (Buffelli, Pasino, & Cangiano, 2001; Changeux, Duclert, & Sekine, 1992; Correia‐de‐Sá & Ribeiro, 1994; Fernandez, Ross, & Nadelhaft, 1999; Kimura, Okazaki, & Nojima, 1997; Machado et al., 2016; Rossi, Dickerson, & Rotundo, 2003; Salim, Dezaki, Tsuneki, Abdel‐Zaher, & Kimura, 1998). Possible release of endogenous CGRP in response to ryanodine application at resting motor synapses and acute physiological consequences of this release on quantal ACh secretion have not been described yet.…”

Sustained synaptic-vesicle recycling by bulk endocytosis contributes to the maintenance of high-rate neurotransmitter release stimulated by glycerotoxin

“…Other excitatory neurotoxins, such as -LTX or trachynilysin, have been shown to promote the selective depletion of small synaptic vesicles Matteoli et al, 1988). These two neurotoxins stimulate asynchronous neurotransmitter release at a similar rate to GLTx, but this rapidly results in a full blockade of neurotransmitter release caused by the depletion of synaptic vesicles Tsang et al, 2000).…”