Bolus intravenous injection of obestatin does not change blood pressure level of spontaneously hypertensive rat

Ghrelin, an endogenous ligand for the GH secretagogue receptor, has been shown to decrease arterial pressure. Obestatin, a sibling of ghrelin derived from preproghrelin, opposes several physiological actions of ghrelin. The aim of this study was to determine the effects of bolus intravenous injection of obestatin on blood pressure in spontaneously hypertensive rats. Three different dosages of obestatin (10, 50, and 100 mu g/kg) and one dosage of ghrelin (10 mu g/kg) were applied. The mean arterial pressure and heart period were continuously recorded for 30 min after injection of drugs. Baroreflex sensitivity was also investigated. In this study, we first demonstrated that intravenous injection of obestatin showed no significant effects on mean blood pressure (10 mu g/kg: 113.8 +/- 2.0 mmHg vs. 114.4 +/- 1.6 mmHg; 50 mu g/kg: 110 +/- 2.4 mmHg vs. 109 +/- 3.2 mmHg; 100 mu g/kg: 115.9 +/- 1.5 mmHg vs. 115.8 +/- 2.4 mmHg; all P > 0.05), heart period (10 mu g/kg: 184.7 +/- 3.9 ms vs. 185.5 +/- 4.1 ms: 50 mu g/kg: 185.9 +/- 4.1 ms vs. 193.4 +/- 4.5 ms; 100 mu g/kg: 137.7 +/- 4.5 ms vs. 143.9 +/- 5.6 ms; all P>0.05), or baroreflex sensitivity (10 mu g/kg: 0.414 +/- 0.03 ms/mmHg vs. 0.442 +/- 0.02 ms/mmHg; 50 mu g/kg: 0.453 +/- 0.04 ms/mmHg vs. 0.439 +/- 0.01 ms/mmHg: 100 mu g/kg: 0.398 +/- 0.02 ms/mmHg vs. 0.401 +/- 0.01 ms/mmHg; all P>0.05), however, intravenous injection of ghrelin could decrease mean arterial pressure (115.9 1.5 mmHg vs. 108.6 +/- 3.6 mmHg, P < 0.01) and increase heart period (132.4 +/- 2.8 ms vs. 152.6 +/- 7.4 ms, P < 0.05), but did not change baroreflex sensitivity (0.36 +/- 0.009 ms/mmHg, P > 0.05) in spontaneously hypertensive rats. (C) 2009 Elsevier Inc. All rights reserved.