Visualization of dopamine D2 binding sites on human inferior vagal ganglia.

The present study used in vitro autoradiography to assess whether high affinity D2 binding sites are present on sections of human inferior vagal ganglia, where arterial baroreceptor primary afferent cell bodies are located. Incubation of tissue sections with [125I]NCQ 298 (0.5 nM) revealed dense but non-uniform binding, with a well-defined topography, consistent with the localization of binding sites over cell bodies rather than nerve axons. Coincubation with the D2 antagonist raclopride (10 microM) completely abolished binding of [125I]NCQ 298. Densitometric quantification of autoradiograms estimated 82 +/- 4% specific binding for [125I]NCQ 298 (0.5 nM). These observations indicate the presence of D2 binding sites on sensory ganglia involved in cardiovascular control pathways in the human, and may help to explain some of the documented cardiovascular effects of dopamine.