Neurotensin and growth hormone-releasing factor-containing neurons projecting to the median eminence of the rat: a combined retrograde tracing and immunohistochemical study.

The origins of the neurotensin (NT)-containing nerve terminals in the median eminence were determined in rats by a combination of retrograde labeling with True blue and immunofluorescence staining. Moreover, the distribution of NT and growth hormone-releasing factor (GRF) was analyzed in the arcuate nucleus (ARC) with an elution-restaining procedure. The retrogradely labeled NT neurons were found mainly in the ARC. Only a few labeled NT neurons were seen in the periventricular and the paraventricular nuclei. The elution restaining procedure demonstrated that an average of 43% of the labeled NT cells in the ventral part of the ARC restained for GRF. These findings support the hypothesis of co-expression of NT with GRF from the ARC.