Lower GABAA receptor binding in the amygdala and hypothalamus of spontaneously hypertensive rats

The central GABAergic system is associated with normal blood pressure regulation, but the role of GAGA receptors in genetic hypertension remains unclear. This study was conducted to investigate GABA_A receptor binding in several brain regions of spontaneously hypertensive (SHR) rats during development of hypertension. GAGA_A receptor binding was labeled with [³⁵S]TBPS and was assessed by quantitative autoradiography with the aid of a computer-assisted image analysis system. Densities of GABA_A receptor binding sites were significantly lower in all hypothalamic and amygdaloid nuclei evaluated in 4-week-old SHR rats, when compared with their age-matched normotensive Wistar-Kyoto rats. At 12 weeks of age, GABA_A receptor binding remained significantly lower in the central amygdaloid nucleus and paraventricular hypothalamic nucleus of SHR rats. Collectively, the results suggest that GABA_A receptors in these nuclei are likely to be involved in the initiation and maintenance of hypertension. In conclusion, this study supports a notion that downregulation of GABA_A receptor binding occurs in the hypothalamus and amygdala of SHR rats and may play a role in genetic hypertension.