gamma-Aminobutyric acid receptor (GABA(A)) subunits in rat nucleus tractussolitarii (NTS) revealed by polymerase chain reaction (PCR) and immunohistochemistry

Expression of mRNAs encoding seven GABA, receptor subunits (alpha (1), alph a (2), alpha (3), alpha (5), beta (2), beta (3), gamma (2)) in the nucleus tractus solitarii (NTS) of rat medulla oblongata was examined by reverse tr anscription-polymerase chain reaction (RT-PCR). All subunit mRNAs, except a lpha (5) were clearly detected. Band densities produced by alpha (1), alpha (3), beta (3), and gamma (2) subunits were greater than those correspondin g to beta (2) and alpha (2) transcripts. The localization of these subunits in tissue sections through NTS was examined by immunohistochemistry. The d ifferential patterns of immunoreactivity in neuronal somata and dendrites o f NTS neurons were generally in agreement with the PCR results, confirming that mRNA expression is correlated with receptor protein synthesis. At ultr astructural level, alpha (1), alpha (3), beta (2/3), and gamma (2) subunits were localized in both cytoplasmic and subsynaptic sites, the latter often apposed to GABA immunoreactive synapses. These results suggest that ionotr opic receptors comprising the alpha (1), alpha (3), beta (2/3), and gamma ( 2) may mediate inhibitory GABA responses in the NTS.