subunit of the GABAAA/BZ receptor complex are significantly higher in the amygdala and locus ceruleus of high-LG compared with low-LG offspring. The α1 subunit appears to confer higher affinity for GABA, providing the most efficient form of the GABAA receptor complex, through increased receptor affinity for GABA. The adult offspring of the low-LG mothers actually show increased expression of the mRNAs for the α3 and α4 subunits in the amygdala and the locus ceruleus. Interestingly, the GABAA/BZ receptor composed of the α3 and α4 subunits show reduced affinity for GABA, by comparison with those containing an α subunit. Moreover, the α4 subunit does not contribute to the formation of a BZ receptor site. These differences in subunit expression are highly specific to the amygdala and the locus ceruleus; no such differences are apparent in the hippocampus, hypothalamus, or cortex. Thus, differences in GABAA/BZ receptor binding are not simply due to a deficit in subunit expression in the offspring of the low-LG mothers, but of an apparently “active” attempt to maintain a specific GABAA/BZ receptor profile in selected brain regions.
