Differential Expression of Prolactin Releasing Peptide and Tyrosine Hydroxylase in Fibers Derived from the Same Neurons in the Rat

We found differential expression of two neuronal markers in nerve fibers that came from the same neuronal somata. Prolactin releasing peptide (PrRP) and tyrosine hydroxylase (TH), a catecholamine synthesis rate-limiting enzyme, were differentially distributed in distinct fibers derived from the same neuronal cell body located in the rat medulla oblongata. All PrRP-immunoreactive neurons were catecholaminergic at the cell body level in the nucleus tractus solitarius (NTS) and in the ventral and lateral reticular nuclei (VLRN). However, in the terminal areas such as the bed nucleus of the stria terminalis (BNST) and paraventricular nucleus (PVN), where fibers are projected from both PrRP and TH positive neurons in the NTS and VLRN, dense PrRP immunoreactive fibers were observed that did not contain TH. In the medulla oblongata, proximal fibers near a neuronal cell body that contained both TH and PrRP were diverged into mainly PrRP-positive or mainly TH-positive fibers. These results suggest that TH and PrRP are differentially expressed between fibers from the same cell body. The fibers containing predominantly PrRP have been detected at birth, so the machinery to transport PrRP and TH separately may be established at an embryonic stage.