Perinatal distribution of galanin and galanin receptor-1 mRNA in the rat hindbrain

In situ hybridisation was used to determine the distribution and levels of mRNA for galanin precursor preprogalanin (ppGAL) and galanin receptor-1 (GA L-R1) in the rat hindbrain before and after birth. Quantification of mRNA l evels was performed from E21. Also, immunohistochemistry was used to study GAL-like immunoreactivity (GAL-LI) prenatally. On E16, no expression of ppG AL mRNA could be detected in any areas examined, whereas on E19 low transcr ipt levels were observed. GAL-LI, however, was seen at relatively high leve ls in nerve fibres already on E16, mainly in the areas receiving primary af ferents. Also, GAL-RI mRNA was expressed at high levels in discrete areas o f the hindbrain on E16. On E21 ppGAL mRNA was found in the locus coeruleus (LC), the nucleus of the solitary tract, the dorsal motor nucleus of the va gus (nX), the lateral reticular nucleus (LRn) and superficially along the v entral medullary surface. Expression increased postnatally in all these are as except in nX and LRn. GAL-Ri mRNA, on the other hand, was found to be ex pressed at high levels on E21 in the LC, where levels then decreased on P1. Expression of GAL-RI mRNA was also found in other areas of the brainstem, but here no changes were detected around birth. These findings demonstrate that ppGAL and GAL-RI mRNAs, as well as CAL-LI, are present in the brainste m in the rat fetus and that the changes in expression after birth could be of importance for the newborn in the transition from pre- to postnatal life . (C) 2000 Elsevier Science B.V. All rights reserved.