Involvement of intracellular Ca2+ stores in 3,4-diaminopyridine-evoked [3H]norepinephrine release.
OBJECTIVE
To study the mechanism for 3, 4-diaminopyridine (DAP) evoking external Ca(2+)-independent release of [3H] norepinephrine ([3H] NE).


METHODS
Rat hippocampal slices were preincubated with [3H] NE and superfused with medium. [3H] NE release was determined.


RESULTS
Under Ca(2+)-free conditions, DAP evoked [3H] NE release. In rats pretreated by reserpine, the effect of DAP was no longer detectable. Ca2+ chelator BAPTA-AM potently inhibited DAP-evoked [3H] NE release. Desipramine 100-500 mumol.L-1 strongly induced [3H] NE release in a concentration-dependent manner, whereas caffeine 30-70 mmol.L-1 was slightly effective on [3H]NE release. The blocker of Ca(2+)-induced Ca2+ releasable stores, dantrolene sodium did not attenuate DAP-evoked [3H]NE release.


CONCLUSIONS
In the absence of extracellular Ca2+, DAP evokes exocytotic release of [3H]NE from synaptic vesicles through liberation of internal Ca2+ from inositol 1, 4, 5-trisphosphate-sensitive Ca2+ stores.
Huang
H Y
HY
Shanghai Institute of Physiology, Chinese Academy of Sciences, China.
Zhou
C W
CW
D015761:4-Aminopyridine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000077770:Amifampridine; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D003891:Desipramine / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006624:Hippocampus / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012110:Reserpine / Q000494:pharmacology
D002614:Chelating Agents; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D012110:Reserpine; D015761:4-Aminopyridine; D000077770:Amifampridine; D002118:Calcium; D003891:Desipramine; D009638:Norepinephrine