Immunohistochemical observation of serotonin neurons in newborn mouse and rat brainstem cultures.

Serotonin neurons in newborn mouse and rat brainstem cultures were studied by peroxidase-antiperoxidase immunohistochemistry using a serotonin antibody. The intensity of the immunohistochemical reaction in the neuronal somata decreased gradually with time and was hardly detectable after one month of culturing. On the other hand, the immunoreactivity of the processes noted at the early stages later on became more intense and covered the full extent of the fibers. From the early stages of the cultures, the axon of each serotonin neuron formed not only a network by branching, but also a true anastomosis with the axonal networks of the other serotonin neurons.