In pithed guinea-pigs, general characteristics and the origin of the tachycardia produced by intravenous injection of 5-hydroxytryptamine (5-HT) were analysed. The study was undertaken to provide evidence that the tachycardia results not only from the direct cardiac action of 5-HT, but also from its indirect sympathicomimetic action. The tachycardic response to 5-HT (25-200 μg/kg) was considerable, long-lasting and dose-dependent. During the depolarizing block of the sympathetic ganglia and the adrenal medulla evoked by nicotine, the 5-HT-induced tachycardia was significantly reduced. Moreover, in animals pretreated with reserpine, bretylium or 6-hydroxydopamine the tachycardia was significantly diminished. There was not a significant difference between the reduction of the tachycardic response to 5-HT produced by 6-hydroxydopamine and that produced by nicotine or reserpine. It is concluded that in guinea pigs the positive chronotropic effect of 5-HT is partly due to the release of noradrenaline from sympathetic nerve terminals as the consequence of the activation of cardiac sympathetic ganglia by 5-HT.
|Original language||English (US)|
|Number of pages||2|
|Journal||IRCS Medical Science|
|State||Published - Jan 1 1982|
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)