Subunit composition of strychnine-sensitive glycine receptors expressed by adult rat basolateral amygdala neurons

In neonatal rats, strychnine-sensitive glycine receptors are widely expressed in the spinal cord, brainstem and forebrain. During development, these 'neonatal' receptors are replaced by an adult isoform, the expression of which becomes restricted primarily to brain stem and spinal cord. Unlike most forebrain regions, functional strychnine-sensitive glycine receptors appear to persist within adult rat amygdala. However, the subunit composition of glycine receptors expressed by amygdala neurons and its relationship to the adult isoform in brain stem/spinal cord has not been defined precisely. In this report, we have utilized RT-PCR and single-cell RT-PCR to demonstrate that the 'neonatal' α₂-subunit mRNA persists in adult rat amygdala neurons and is the predominant α-subunit. We further demonstrate that native amygdala glycine receptors are relatively insensitive to the receptor antagonist picrotoxin, suggesting that α₂- and β-subunits may be present together in the same multisubunit complex. We further demonstrate that α₂- and β-subunits cloned from adult rat amygdala can form functional channels when expressed in a heterologous system. Together, these studies highlight both the unique characteristics of strychnine-sensitive glycine receptors in the adult rat amygdala as well as the possibility that α₂/β channels may represent the adult forebrain isoform of the strychnine-sensitive glycine receptor.