Release of zinc sulphide accumulations into synaptic clefts after in vivo injection of sodium sulphide.

The fate of sulphide-bound zinc was studied in synaptic boutons of the telencephalon after intracerebral injection of sodium sulphide. After short survival times (30 min), zinc was found in boutons located in synaptic vesicles, later in vesicles and in the synaptic clefts, and at long survival times (48 h) zinc was located solely in the extracellular space. The present data suggest that: zinc, when bound to sulphide, is released into the synaptic cleft in a time dependent way; and different zinc-containing boutons have different turnover periods, the hippocampal giant mossy fiber boutons being the tardiest to empty their zinc sulphide content.