[Transplantation of serotonin neurons in the olfactory bulb of the adult rat].

Serotonergic neurons have their perikaraya concentrated in the raphe nuclei. In the present experiment, pieces of raphe nuclei containing serotonergic neuroblasts were dissected from 14 days rat embryos, mechanically dissociated, and 1 microliter of a cell suspension containing 30,000 cells was injected slowly under stereotaxic control in the olfactory bulb of adult rats. Three weeks after transplantation, the brain of the rats were processed for immunocytochemical detection of 5-HT. In all of the grafted animals, 5-HT neurons were found in the olfactory bulb. They exhibited the morphology of adult neurons, with well developed axon and dendrites, extending far from the injection site. Ultrastructural immunocytochemistry disclosed afferent and efferent synapses to the grafted neurons. Three preliminary results indicates that the transplanted neurons have been integrated in the host's neuronal circuitry. Ongoing electrophysiological studies are now directed at investigating the functional status of these grafted neurons.