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Release of Purines from Postsynaptic Structures of Amphibian Ganglia
Author(s) -
Rubio R.,
Bencherif M.,
Berne R. M.
Publication year - 1988
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.1471-4159.1988.tb01150.x
Subject(s) - postsynaptic potential , amphibian , purine metabolism , neuroscience , biology , chemistry , biochemistry , ecology , receptor , enzyme
Isolated sympathetic paravertebral ganglia of the frog were incubated for 1 h with [ 3 H]adenosine. Then, after washout of excess label, the contribution of pre‐ and postsynaptic activation on the release of 3 H‐labeled purines was studied. The ganglion was superfused with Ringer's solution at room temperature, and extracellular electrodes were used for stimulation and recording. Preganglionic stimulation enhanced overall release of 3 H‐labeled purines. At rest, the release of 3 H‐labeled purines per minute represented 0.62 ± 0.02% of the total 3 H‐label in the ganglion, and this fraction increased depending on the frequency of orthodromic stimulation. Analyses of the effluent from resting and stimulated ganglia showed that in both cases the nonnucleotide fractions constituted >97% of the total counts in the medium: adenosine (58.4 ± 10.1%); inosine (31.7 ± 12.9%); hypoxanthine (7.1 ± 2.4%); and AMP, ADP, and ATP together (1.6 ± 0.9%) (n = 11). Nucleotides were released, but their levels were not increased significantly during stimulation. Inclusion of ectophosphatase inhibitors slightly enhanced nucleotide release (from 1.1 ± 0.5 to 1.8 ± 0.7%; n = 5) but did not alter the amount of nucleosides. Hence, nucleosides are the main products released by the ganglion and do not arise from hydrolysis of extracellular ATP. Preganglionic stimulation enhanced release of labeled purines, which was frequency dependent from 1 to 20 Hz. Atropine (2 μM) and tubocurarine (150 μM) totally blocked the release of 3 H‐labeled purines associated with preganglionic stimulation. Antidromic stimulation was accompanied by a significant release of labeled purines. Carbachol (10 −6 ‐10 −2 M) induced a dose‐dependent release of 3 H‐labeled purines from the ganglion. These results indicate that the release of nucleosides during synaptic transmission is the result of activation of the postsynaptic structures.