Premium
Mobilization of a Vesamicol‐Insensitive Pool of Acetylcholine from a Sympathetic Ganglion by Ouabain
Author(s) -
Prado Marco Antonio M.,
Gomez Marcus V.,
Collier Brian
Publication year - 1993
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1993.tb03536.x
Subject(s) - ouabain , acetylcholine , synaptic vesicle , superior cervical ganglion , chemistry , sympathetic ganglion , biophysics , egta , vesicle , endocrinology , medicine , biology , calcium , biochemistry , membrane , sodium , organic chemistry
These experiments investigate the release of transmitter from the perfused superior cervical ganglia of cats induced by ouabain in the absence or presence of 2‐(4‐phenylpiperidino)cyclohexanol (vesamicol), a blocker of acetylcholine (ACh) uptake. Ouabain, perfused through the ganglia, released ACh in a Ca 2+ ‐dependent way. Vesamicol caused some inhibition of the release of ACh by ouabain; however, under this condition, the Na + , K + ‐ATPase inhibitor released five times more transmitter than did preganglionic stimulation at 5 Hz. Also, when ganglia exposed to vesamicol were depleted of the impulse‐releasable pool of ACh, subsequent perfusion with ouabain released ACh, and this included ACh newly synthesized in the presence of vesamicol; this phenomenon could be inhibited by the lack of Ca 2+ and presence of EGTA, and was completely abolished by perfusion with a medium containing 18 m M Mg 2+ . To test whether the release of this vesamicol‐insensitive Ca 2+ ‐dependent pool by ouabain is associated with a decrease in the number of synaptic vesicles, ganglia treated with the ATPase inhibitor after the depletion of the impulse‐releasable pool of ACh were fixed for electron microscopy. In the presence of Ca 2+ , coincident with the release of the vesamicol‐insensitive pool of ACh, nerve terminals were almost depleted of synaptic vesicles; ganglia treated similarly, but with medium containing 18 m M Mg 2+ instead of Ca 2+ , were not depleted of synaptic vesicles. These results suggest that ouabain releases a vesamicol‐insensitive pool of ACh from the sympathetic ganglion and also support the notion that this compartment is vesicular and its exocytosis depends on extracellular Ca 2+ . It is suggested that empty‐vesicle recycling in the presence of vesamicol restricts mobilization of full vesicles to release sites.