Distribution of prolactin-releasing peptide mRNA in the rat brain

In order to identify the distribution of prolactin-releasing peptide (PrRP) mRNA in the rat brain, we independently cloned cDNA of PrRP. Brains were r emoved from three adult males, and brains from three females each at 0200 a nd 1400 h on day 7 of pregnancy were obtained. By the non-radioactive in si te hybridization method, the location of PrRP mRNA was detected in very res tricted brain areas. The distribution of PrRP mRNA signals was very similar in both sexes. In the hypothalamus, only the ventral part of the caudal do rsomedial nucleus had PrRP mRNA signals. Other forebrain areas did not show any positive signals. In the medulla oblongata, two discrete areas contain ed PrRP mRNA signals. No positive signal was found in the rostral part of t he medulla oblongata extending to the anterior part of the area postrema. T he caudal part of the nucleus of the solitary tract (NTS) had neurons with very strong signals of PrRP mRNA. The reticular nucleus showed a few PrRP m RNA positive neurons. The number of PrRP mRNA positive cells in the NTS was not different between experimental groups, although plasma prolactin level s in these animals were different. This anatomical information on the locat ion of PrRP mRNA in the brain provides the framework to understand the phys iological functions of PrRP in vivo. (C) 2000 Elsevier Science Inc.