THE EFFECT OF TETRODOTOXIN AND CADMIUM ON HIPPOCAMPAL NORADERNALINE AND 5-HYDROXYTRYPTAMINE RELEASE AND TURNOVER

Using the technique of in vivo microdialysis, we examined the relationship between neuronal firing and neurotransmitter release and metabolism in the hippocampus) The neurotoxin tetrodotoxin (TTX) was applied locally to block voltage-sensitive sodium channels) and extracellular Ca was replaced with cadmium (Cd ) to inhibit Ca dependant neurotransmitter release. The effectes of these drugs on both noradrenergic and serotonergic transmitter system were evaluated. The results show that 5-HT and NA release in hippocampal nerve terminal are active process and depend on the cell firing and influx of Ca ions prior to release. 5-HTand NA synthesis and turnover are also decreased by 1TX and Cd ) these decays are greater in the absence of Ca ions. this suggest an essential role of ca ions for hippocampal monaoamine synthesis and turnover.