Gene expression of OGFr in the developing and adult rat brain and cerebellum

The native opioid peptide, [Met⁵]-enkephalin (termed opioid growth factor (OGF)), is a tonically active negative growth factor targeted to cell proliferation in the developing nervous system. OGF action is mediated by the OGF receptor (OGFr). The present study investigates gene expression of OGFr in the developing and adult brain and cerebellum of the rat using Northern blot analysis and normalization to GAPDH. OGFr was detected in whole brain at embryonic day 20 and birth, and was at least twofold greater than neonatal levels during the first week of life. From postnatal day 15 onwards to adulthood, levels of OGFr mRNA in the whole brain were detectable but less than those at birth. OGFr mRNA in cerebellum was found on embryonic day 20, and remained relatively constant until postnatal day 12 when a sharp increase was recorded. In the third week of life and continuing into adulthood, cerebellar OGFr mRNA was detected at levels comparable to those in postnatal week 1. These results show that message for OGFr is developmentally regulated prior to and after birth, is ubiquitously expressed during development, and is present in the adult brain and cerebellum even though OGF receptor binding is not recorded.