Adenosine deaminase-containing hypothalamic neurons accumulate 5-hydroxytryptophan: a dual-colour immunofluorescence...

Neurons of the posterior hypothalamic magnocellular nucleus (PHMN) in the rat are immunoreactive for adenosine deaminase (ADA) and cells coextensive with this nucleus show immunoreactivity for serotonin after pretreatment with 5-hydroxytryptophan (5-HTP). The degree to which ADA coexists in cells having 5-HTP uptake capability was analyzed by a new double immunohistofluorescence procedure employing diethylaminocoumarin (DAMC). It was determined that 5-HTP accumulating cells of the PHMN represent a subpopulation of those immunoreactive for ADA. These results add further to the neurochemical characterization of this globally projecting hypothalamic cell group and point out the utility of DAMC as a new immunohistofluorescence marker.