GABAa α1 and α2 receptor subunit expression in rostral ventrolateral medulla in nonpregnant and pregnant rats

As most of you already know the RVLM contains the neurons responsible for excitatory input to preganglionic sympathetic neurons that produce vasoconstriction and increases in heart rate and contractility--- and you all definitely know that the neurotransmitter GABA inhibits sympathetic transmission in the RVLM. GABA_A receptors are heteroligomeric proteins that form ligand gated Cl^- channels. Expression of the different subunits can be regulated by numerous physiologic and pathophysiologic conditions. In this study the effects of pregnancy hormones (specifically estrogen and progesterone) on the expression of GABA_A subunits α_1-3. Foley et al. hypothesized that GABA_A receptors in the RVLM of late term pregnant rats may have higher expression of α₁GABA_A receptor subunit than the expression of α₂ or α₃ subunits.

Using PCR, quantitative PCR and immunoblots as their methods they set out to identify if there was indeed an effect by the progesterone metabolite 3α -OH-DHP (3α -hydroxy-dihydroprogesterone) on the α₁ receptor. The results showed that in the RVLM, the levels of GABA_A α₁ and α₂ receptor subunit mRNA and protein were similar between nonpregnant and late term pregnant rats, and the ration of GABA_A α₁ and α₂ receptor subunit mRNA expression was not different between groups. It seems that further studies have to be conducted on different GABA subunits that can be affected by neurosteroids.