Effect of chemical sympathectomy on (−)‐isoprenaline‐induced changes in cardiac β‐adrenoceptor subtypes in the guinea‐pig and rat

Andrew R. Kompa, Peter Molenaar, Roger J. Summers

Research output: Contribution to journalArticleResearchpeer-review

10 Citations (Scopus)

Abstract

1 Quantitative autoradiography was used to determine β‐adrenoceptor densities in cardiac regions of guinea‐pigs and rats after chemical sympathectomy with 6‐hydroxydopamine, and to examine how chemical sympathectomy affected β‐adrenoceptor changes following infusion of (‐)‐isoprenaline (400 μg kg−1 hr−1, 7 days). 2 Seven days after 6‐hydroxydopamine (100 mg kg−1, i.v.), cardiac tissue levels of noradrenaline were reduced by 94.0± 3.5% (guinea‐pig) and 86.0 ± 7.0% (rat). The blood pressure increase in rats to tyramine (0.5 mg, i.v.) was reduced from 118 mmHg in 6‐hydroxydopamine‐treated animals. 3 There were no changes 7 and 14 days after 6‐hydroxydopamine treatment in total, β1‐ and β2‐adrenoceptor density in the atrioventricular conducting system and atrial and ventricular myocardium in both species. 4 In control animals, (‐)‐isoprenaline infusion produced selective reductions in β2‐adrenoceptor density, whilst β1‐adrenoceptor density remained unchanged. 5 In 6‐hydroxydopamine treated guinea‐pigs or rats, (‐)‐isoprenaline infusion caused no change in β1‐radrenoceptors except in the right bundle branch whilst β2‐adrenoceptors were reduced in the atrioventricular conducting system (atrioventricular node, bundle of His, right and left bundle branches) and myocardium (interventricular septum and atria). 6 The differential effect of (‐)‐isoprenaline on β1‐and β2‐adrenoceptors is not therefore due to the occupation of β1‐adrenoceptors by noradrenaline or to prior down‐regulation of β1‐adrenoceptors by noradrenaline, since it persists after depletion of noradrenaline.

Original languageEnglish
Pages (from-to)411-423
Number of pages13
JournalJournal of Autonomic Pharmacology
Volume14
Issue number6
DOIs
Publication statusPublished - 1 Jan 1994

Cite this