Pregnancy results in attenuated baroreflex mediated sympathoexcitatory responses which may be due to potentiation of γ-aminobutyric acid (GABA) inhibition in the rostral ventrolateral medulla (RVLM). The major metabolite of progesterone, 3α-hydroxy-dihydroprogesterone (3α-OH-DHP), which is elevated in pregnancy, is a potent neurosteroid positive modulator of GABAA receptors, and sensitivity of GABAA receptors to 3α-OH-DHP is dependent on the receptor subunit composition. The purpose of this study was to evaluate the GABAA α1 and α2 receptor subunit mRNA and protein expression in the RVLM of nonpregnant and late term pregnant rats. Micropunches of RVLM were collected from nonpregnant and late term pregnant rats and the expression levels of GABAA α1 and α2 receptor subunits were analyzed using quantitative competitive reverse transcriptase polymerase chain reaction (RT-PCR) and immunoblot techniques. The competitive RT-PCR analysis allows comparison of expression levels between different mRNA, and the mRNA expression level of GABAA α1 was several hundred fold greater than GABAA α2 in both groups. However, this relative distribution of GABAA α1 and α2 receptor subunits protein or mRNA expression was not altered in late term pregnant compared to nonpregnant rats. These data demonstrate, that within the RVLM of both nonpregnant and late term pregnant rats, the relative expression levels of GABAA α1,2 receptor subunits favor GABAA receptors susceptible to positive modulation by progesterone metabolites.
- Competitive RT-PCR
- Gene expression
- Reverse transcriptase polymerase chain reaction
- Western blot analysis
- γ-Aminobutyric acid receptor