[Capture and fixation of tritiated serotonin by chick embryo notochord]

The 3 day old Chick notochord capacity to fix tritiated serotonin is maximal in its axis and in cephalic region. Our observations permitting us to find, the intracellular serotonin binding sites, contribute to an explanation of the capture mechanism and suggest a special direct role of the notochord on the monoaminergic neuron cytodifferentiation.