Evidence for corticotropin releasing factor and Leu-enkephalin in the neural projection from the lateral parabrachial nucleus to the median preoptic nucleus: a retrograde transport, immunohistochemical double labeling study in the rat.

Neurons in the lateral parabrachial nucleus of the pons were retrogradely labeled by True Blue deposited into the median preoptic nucleus. Immunohistochemical staining indicated that some 7% of these cells also contained corticotropin releasing factor, and another 5% were stained for Leu-enkephalin. Labeled cells were not found throughout the lateral parabrachial nucleus, but were confined to distinct cytoarchitectonically defined subdivisions. These findings suggest the presence of two peptides that have been implicated in central cardiovascular control within a neural projection between two cell groups that have been similarly implicated. The origins of the presently described pathways in distinct parts of the lateral parabrachial nucleus suggest an underlying topographical organization of this cell group that had not previously been appreciated.