Developmentally Regulated Expression of HDNF/NT‐3 mRNA in Rat Spinal Cord Motoneurons and Expression of BDNF mRNA in Embryonic Dorsal Root Ganglion

Publisher Website
Google Scholar
Abstract
Northern blot analysis was used to demonstrate high levels of hippocampus-derived neurotrophic factor/ neurotrophin-3 (HDNF/NT-3) mRNA in the embryonic day (E) 13–14 and 15–16 spinal cord. The level decreased at E18–19 and remained the same until postnatal day (P) 1, after which it decreased further to a level below the detection limit in the adult. In situ hybridization revealed that the NT-3 mRNA detected in the developing spinal cord was derived from motoneurons and the decrease seen at E18–19 was caused by a reduction in the number of motoneurons expressing NT-3 mRNA. The distribution of NT-3 mRNA-expressing cells in the E15 spinal cord was very similar to the distribution of cells expressing choline acetyltransferase or nerve growth factor receptor (NGFR) mRNA. Moreover, a striking similarity between the developmentally regulated expression of NT-3 and NGFR mRNA was noted in spinal cord motoneurons. A subpopulation of all neurons in the dorsal root ganglia expressed brain-derived neurotrophic factor (BDNF) mRNA from E13, the earliest time examined, to adulthood. These results are consistent with a trophic role of NT-3 for proprioceptive sensory neurons innervating the ventral horn, and imply a local action of BDNF for developing sensory neurons within the dorsal root ganglia.