Lithium-induced norepinephrine release from hippocampal slices in the absence of extracellular Ca2+

Slices of rat hippocampus, preincubated with [3H] norepinephrine ([3H]NE) were superfused with Ca(2+)-free medium containing desipramine 1 mumol.L-1, Li+ (40-80 mmol.L-1) evoked [3H]NE release in a concentration dependent manner. It was enhanced by 4 beta-phorbol 12,13-dibutyrate (PDB) and inhibited by tetrodotoxin. Ca(2+)-chelator BAPTA-AM did not attenuate this Li-evoked [3H]NE release. After application of 3,4-diaminopyridine to evoke [3H]NE release and PDB to enhance this release, the Li(+)-evoked [3H]NE release was significantly inhibited. The findings suggest that the liberation of internal Ca2+ stores was not involved in this release process.