Pineal methoxyindoles depress calcium uptake by rat brain synaptosomes

The effect of several pineal methoxyindoles on 45Ca 2+-uptake was examined in a crude synaptosome preparation from adult rat brains. 5-Methoxytryptol, 5-methoxytryptamine, melatonin and 6-chloromelatonin (10 −8–10 −6 M) depressed significantly the K +- stimulated increase in Ca 2+-uptake, without affecting the basal, unstimulated Ca 2+-uptake by synaptosomes. At 10 −6 M concentration the following order of potency was found: 6-chloromelatonin⩾5-methoxytruptamine>5-methoxytryptophol⩾melatonin. Serotanin did not affect significantly either basal or stimulated Ca 2+-uptake.