Alpha-blockade and vasodilatation induced by nipradilol, arotinolol and labetalol in pithed rats.

Abstract

In pithed rats two recently-introduced beta-blockers, nipradilol and arotinolol, as well as labetalol shifted the pressor dose-response curve for phenylephrine to the right. Labetalol and arotinolol did not modify the pressor dose-response curve for clonidine, while nipradilol induced a definite rightward shift. These results indicate that labetalol and arotinolol are selective alpha 1-blockers, while nipradilol is a non-selective one. In addition, all the three beta-blockers produced complex changes in the blood pressure in pithed rats. A fall of the diastolic blood pressure induced by labetalol and nipradilol was preceded by a slight rise, while arotinolol produced a fall at lower doses and a rise at higher ones. The hypotension by labetalol was abolished after propranolol, while the hypertension was suppressed by prazosin, indicating that labetalol has an intrinsic beta- and alpha 1-sympathomimetic effect. The hypertension and the hypotension produced by nipradilol and arotinolol persisted even in the presence of propranolol and prazosin or propranolol and yohimbine.

• Authors: Y Nakagawa, H Nakahara, W P Chin, S Imai
• Journal: Japanese journal of pharmacology (Jpn J Pharmacol) Vol. 39 Issue 4 Pg. 481-5 (Dec 1985) ISSN: 0021-5198 [Print] Japan
• PMID: 2419612 (Publication Type: Journal Article)

Chemical References

• Adrenergic alpha-Antagonists
• Adrenergic beta-Antagonists
• Propanolamines
• Phenylephrine
• Yohimbine
• arotinolol
• nipradilol
• Clonidine
• Labetalol
• Prazosin

Topics

• Adrenergic alpha-Antagonists (pharmacology)
• Adrenergic beta-Antagonists (pharmacology)
• Animals
• Blood Pressure (drug effects)
• Clonidine (pharmacology)
• Decerebrate State
• Labetalol (pharmacology)
• Male
• Phenylephrine (pharmacology)
• Prazosin (pharmacology)
• Propanolamines (pharmacology)
• Rats
• Rats, Inbred Strains
• Vasodilation (drug effects)
• Yohimbine (pharmacology)