Identification of dopamine and growth hormone-releasing factor-containing neurons projecting to the median eminence of the rat by combined retrograde tracing and immunohistochemistry.

The topographical location of tyrosine hydroxylase (TH) neurons, a marker for dopamine neurons in the hypothalamus, that project to the median eminence was identified with immunofluorescence staining in combination with retrograde transblue, indicating that they projected to the median eminence. Only a few retrogradely labeled TH cells were observed in the periventricular nucleus and the lateral basal hypothalamus. The elution restaining procedure revealed that an average of 32% of the labeled TH cells in the ventrolateral portion of the ARC contained GRF. These findings support the hypothesis of co-expression of dopamine with GRF from the ARC.