Distribution and developmental changes in metabotropic glutamate receptor messenger RNA expression in the rat lumbar spinal cord

Using in situ hybridisation, the regional distribution of primary transcrip ts and splice variants of all metabotropic glutamate receptor subtypes (mGl uR) currently known to be expressed in the spinal cord have been studied in the lumbar enlargement of the rat spinal cord. In adult animals, the messe nger RNA of the mGluR subtypes 1, 5, 3, 4 and 7 were differentially express ed. The transcripts of mGluR1 and 5 were most abundant with mGluR5 messenge r RNA being concentrated in the superficial dorsal horn. In contrast, the m GluR2 transcript was not detectable with the sensitivity of the method. Sec ondly, age related changes (postnatal days 1, 7, 12, 21) in the postnatal e xpression of mGluR1-5 and 7 transcripts have been investigated. mGluR 1 and 7 messenger RNA showed a general decrease in spinal expression from postna tal day 1 to day 21. Quantitative densitometry showed high mGluR3 and 5 mes senger RNA levels especially in the superficial dorsal horn at birth, howev er these levels decreased with age. In addition to changes in density, the regional distribution of mGluR3 messenger RNA was altered with postnatal de velopment. Up to postnatal day 12, mGluR3 messenger RNA expression was almo st exclusively restricted to the spinal grey matter, but with postnatal day 21 a strong additional expression in the white matter occurred. Distributi on of mGluR4 messenger RNA showed little change in the dorsal horn, however motoneuronal expression emerged during development. These changes may sugg est different roles for mGluRs in the maturation of spinal transmission of the rat nervous system (C) 1999 Elsevier Science B.V. All rights reserved.