The effects of inorganic lead on the spontaneous and potassium-evoked release of 3H-5-HT from rat cortical synaptosome interaction with calcium.

Interaction of lead with the serotonergic system has been studied in vitro in rat brain synaptosomal fraction prepared from cortical tissue. Synaptosomes were loaded with 3H-5-HT and spontaneous and K+-evoked release of the amine was examined in the presence and the absence of calcium. It was shown that lead itself induced the release of 3H-5-HT (EC50 = 27 microM). This effect decreased (40%) in the presence of calcium without modification of the EC50. Moreover, lead markedly inhibited the K+-evoked release of 3H-5-HT observed in the presence of calcium. This effect was obtained either in the presence of lead or using synaptosomes pretreated with lead and washed. These results indicate that lead interferes with neuronal 5-HT release by mechanism(s) involving calcium.