AGE-RELATED DEVELOPMENT OF GAMMA-AMINOBUTYRIC-ACID (GABA)(B) RECEPTORFUNCTIONS IN VARIOUS BRAIN-REGIONS OF SPONTANEOUSLY HYPERTENSIVE RATS

The age-related development of GABA(B) receptors and their coupling to adenylate cyclase were studied in the brains of spontaneously hyperte nsive (SHR) and normotensive Wistar-Kyoto (WKY) rats. Compared with WK Y rats, the specific [H-3]GABA binding to GABA(B) receptors showed a s ignificant decrease not only in the posterior hypothalamus, midbrain, hippocampus and striatum of eleven-week-old SHR, which maintain a hype rtensive state, but also in the posterior hypothalamus of four-week-ol d normotensive SHR. Similarly, the GABA(B) receptor agonists (baclofen and DN-2327)-induced suppression of adenylate cyclase activity showed a decrease in the posterior hypothalamus of four-week-old SHR as well as in the posterior hypothalamus and striatum of eleven-week-old SHR. These results suggest that the functions of the GABA(B) receptor in t he brain of SHR may be decreased independently from the occurrence of blood pressure elevation and that such changes may even be involved in the pathogenesis of SHR.