Synaptic connections between serotoninergic axon terminals and tyrosine hydroxylase-immunoreactive neurons in the arcuate nucleus of the rat hypothalamus. A combination of electron microscopic autoradiography and immunocytochemistry.

A combination of electron microscopic autoradiography and immunocytochemistry was used to examine the connections between serotoninergic axons and dopaminergic neurons of the arcuate nucleus of the rat hypothalamus. The serotoninergic elements were identified after selective uptake of tritiated serotonin and the dopaminergic neurons with tyrosine hydroxylase cytochemistry. Synaptic junctions between labeled serotoninergic nerve endings and tyrosine hydroxylase-immunoreactive neurons were observed, providing a structural basis for a direct influence of serotoninergic elements on tuberoinfundibular dopaminergic neurons.