Pindolol increases plasma norepinephrine concentration by stimulation of beta 2-adrenoceptors in conscious spontaneously hypertensive rats.
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| Abstract |
The beta-adrenoceptor antagonist pindolol [10-1,000 micrograms/kg subcutaneously (s.c.)] caused dose-related decreases in mean arterial pressure (MAP) and increased heart rate (HR) in conscious spontaneously hypertensive rats (SHR). The lowest dose of pindolol (10 micrograms/kg) decreased MAP by 25 mm Hg (-16%) without affecting plasma norepinephrine (NE) or plasma renin concentration (PRC). However, higher doses of pindolol elicited dose-related increases in plasma NE concentration and PRC. Plasma epinephrine concentration was not altered by pindolol. The selective beta 2-adrenoceptor antagonist ICI 118,551 (3 mg/kg, s.c.) prevented the tachycardia but not the increase in PRC caused by 100 micrograms/kg pindolol. Treatment with ICI 118,551 completely eliminated the 45% increase in plasma NE elicited by 100 micrograms/kg of pindolol even though the decrease in MAP caused by this dose of pindolol was the same in the presence (-33 mm Hg) and absence (-34 mm Hg) of beta 2-adrenoceptor blockade. These results indicate that the vasodepressor action of pindolol in SHR does not result from an agonistic effect at postjunctional beta 2-adrenoceptors in the vasculature. In addition, the increases in plasma NE concentration produced by pindolol result from stimulation of beta 2-adrenoceptors. These beta 2-adrenoceptors may be located prejunctionally on sympathetic neurons.
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| Authors | T K Keeton |
| Journal | Journal of cardiovascular pharmacology (J Cardiovasc Pharmacol) Vol. 16 Issue 3 Pg. 354-9 (Sep 1990) ISSN: 0160-2446 [Print] United States |
| PMID | 1700204 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.) |
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