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.
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.
D000818:Animals; D001180:Arthropod Venoms / Q000494:pharmacology*; D015740:Calcitonin Gene-Related Peptide; D005089:Exocytosis / Q000187:drug effects*; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D009469:Neuromuscular Junction / Q000032:analysis*; D009479:Neuropeptides / Q000032:analysis*; D011894:Rana pipiens; D013111:Spider Venoms / Q000494:pharmacology*; D013572:Synaptic Vesicles / Q000166:cytology*
D001180:Arthropod Venoms; D009479:Neuropeptides; D013111:Spider Venoms; C020763:alpha-latrotoxin; D015740:Calcitonin Gene-Related Peptide