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[ 3 H]Dopamine Depletion from Osmotically Defined Storage Sites: Effects of Reserpine, 53 m M KC 1 , and d ‐Amphetamine
Author(s) -
Takimoto Glenn S.,
Stittsworth James D.,
Stephens Janet K.
Publication year - 1983
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.1471-4159.1983.tb11822.x
Subject(s) - reserpine , dopamine , chemistry , amphetamine , neurotransmitter , synaptosome , amine gas treating , endocrinology , medicine , chromatography , biophysics , in vitro , biochemistry , biology , receptor , organic chemistry
A crude synaptosome‐containing fraction (P 2 ′) prepared from rat striatal slices incubated with [ 3 H)dop‐amine was exposed to hypoosmotic conditions and rapidly subjected to Millipore filtration. P 2 ′‐associated [ 3 H]dopamine trapped on the filters was defined as hypoosmotic resistant, whereas P 2 ′‐associated [ 3 H]dop‐amine that washed through the filters was defined as hypoosmotic sensitive. Electron microscopic examination of sections prepared from a P 2 ’pellet that had been exposed to hypoosmotic conditions revealed extensive synaptosomal lysis. [ 3 H]Dopamine accumulation and retention by the hypoosmotic‐resistant fraction were reduced by reserpine. The proportional distribution of [ 3 H]dopamine between hypoosmotic‐resistant and ‐sensitive fractions was measured following in vitro exposure of the preloaded P 2 ’fraction to reserpine, 53 mM KC 1 , and d ‐amphetamine. Each of these treatments resulted in a time‐dependent loss of [ 3 H]dopamine from the loaded P 2 ’fraction without eliciting an alteration in the proportional distribution of [ 3 H]dopamine between hypoosmotic‐resistant and ‐sensitive fractions. Release induced by reserpine and d ‐amphetamine was independent of extrasyn‐aptosomal Ca 2+ , whereas 53 m M KCl‐induced release was dependent on extrasynaptosomal Ca 2+ . These results suggest that dopamine may be rapidly equilibrated between osmotically defined storage compartments, and thus specific compartmental depletion of loaded [ 3 H)dop‐amine cannot be identified on the basis of osmotic lability.