Postnatal developmental regulation of neuronal nicotinic receptor subunit α7 and multiple α4 and β2 mRNA species in the rat

Abstract This study examined the postnatal development of neuronal nicotinic receptor (nAChR) α 7, α 4 and β 2 subunit mRNA in the Sprague Dawley rat brain. The hippocampus, septum and cortex were removed on postnatal day 1 (P1), P7, P14, or P28 and analyzed by sex. Northern analysis of cortical and pooled hippocampal and septal total RNA with 32 P - α -dCTP-labeled α 7, α 4 (recognizing α 4.1 and α 4.2 mRNA), and β 2 nAChR cDNA probes identified three (2.4, 3.8 and 8.0 kb) α 4, four (3.5, 5.0, 7.5 and 10.0 kb) β 2 and a single 5.7 kb α 7 mRNA species. Cortical α 4 mRNA peaked on P14 and remained high on P28, whereas hippocampal/septal α 4 mRNA was higher on P7 and P14 than on P1 and P28. Expression of cortical and hippocampal/septal β 2 mRNAs decreased on P7, followed by a dramatic peak on P14. α 7 mRNA peaked on P7. Throughout development, 2.4 kb α 4 mRNA was more intense than 3.8 kb α 4 mRNA, whereas 5.0 kb β 2 mRNA was the most intense cortical and hippocampal/septal β 2 mRNA species. The α 4.1-specific cDNA probe detected similar-sized α 4 bands as the pan-specific α 4 cDNA probe, therefore precluding the identification of any band as α 4.2-specific. These results suggest that postnatal expression of α 4 and α 7 but not β 2 mRNAs is brain region-specific, and that the contribution of multiple nAChR subunit mRNA species in development may vary.