Hipothalamic Beta Adrenergic Blockade: Cardiovascular Effects and Actions on the Aminergic Neutotransmission

pp 188-193

Abstract

The aim of this work was to study the intrahypothalamic actions of metoprolol on blood pressure and dopaminergic and serotoninergic neurotransmission in sham operated (SO) and aortic coarctated (ACo) rats by using the microdialysis perfusion technique. Wistar urethane anesthetized rats were used. A canula was inserted in the carotid artery. A concentric microdialys is probe was implanted into the anterior hypothalamus (AH) and metoprolol (6 pg/ml) was perfused through the probe. Change on mean arterial pressure (MAP)and heart rate (HR) were measured. DOPAC and5-HIAA levels were measured in dialysate samples by HPLC-EC. Perfusion of metoprolol in AH cause a significant decrease of MAP in ACo rats (AMAP:-12 ± 1 mm Hg; n = 5; p < 0.05 versus SO rats) but not in SO group. We also found a significant de-crease of HR in ACo rats (\HR: -22 ± 6 bpm; n = 5;p < 0.05 versus SO rats) but not in SO rats. In theAH dialysate of ACo rats we observed a significant increase of DOPAC levels (16 ± 4%; n = 5; p <0.05 versus SO rats). On the other hand, in the AH dialysate we not found significative change of 5-HIAA levels in both experimental groups. The results suggest that the intrahypothalamic perfusion of metoprolol produce cardiovascular actions in the ACo rats. On the other hand, the perfusion produce changes in the dopaminergic neurotransmission in ACo rats, but not in the serotoninergic neurotransmission of both experimental groups.