Developmental changes in the expression of GABA A receptor subunits α1, α2, and α3 in brain stem nuclei of rats

Abstract

Gamma-aminobutyric acid (GABA) A receptor subunit switching is a suggested postnatal mechanism for changes in GABA transmission from depolarization to hyperpolarization. Previously, we found an apparent switch between GABA A α3 and α1 subunit expression in the rat pre-Bötzinger complex (PBC) on postnatal day (P) 12, a presumed peak critical period of respiratory nuclei development. The present study aimed at determining if GABA A subunit switching occurred in another respiratory nucleus, the ventrolateral subnucleus of the solitary tract nucleus (NTS VL), and in a non-respiratory cuneate nucleus (CN) of P0 to P21 rats. In both nuclei: (1) the expression of GABA A α1 subunit was relatively low at birth but increased with development; (2) that of GABA A α3 was relatively high at birth but declined with age; and (3) GABA A α2 remained relatively low and constant throughout development. However, the specific patterns differed between the two nuclei, but were similar between the NTS VL and the PBC. In the NTS VL, GABA A α1 expression gradually increased from birth and peaked at P12, whereas that in the CN sharply rose from P7 and peaked at P10. GABA A α3 expression had a prominent decrease from P11 to P12 in the NTS VL, whereas that in the CN only gradually declined from P10 to P12. The developmental trends of α1 and α3 in the NTS VL intersected close to P12, whereas those in the CN intersected at P10. Despite differences in timing, GABA A α subunit switching may be a common theme in the brain stem that may mediate different functional properties of GABA transmission.