Key result
UK42620 drives inotropic and chronotropic responses via tyramine-like noradrenaline release and prejunctional alpha-2 activity.
Why the study?
The pharmacological actions of the morpholinocatechol compound UK42620, including its clonidine- and tyramine-like effects, were studied to characterize its effects on noradrenaline release and atrial function.
UK42620 is a morpholinocatechol compound that exhibits dual pharmacological actions, acting both as a tyramine-like noradrenaline releaser and a clonidine-like prejunctional alpha2-adrenoceptor agonist in rat atria.
The actions of a morpholinocatechol (UK42620) were studied in rat isolated atria preparations consisting of spontaneously beating left and right atrial pairs. 2. UK42620 produced positive inotropic and chronotropic responses and, in atria that were incubated with [(3)H]-noradrenaline, it also produced a massive increase in the release of radioactivity. 3. These actions of UK42620 were similar to those of tyramine and were blocked by the beta-adrenoceptor antagonist propranolol (0.3 microM) and by the neuronal uptake blocker desipramine (1 microM). 4. In the presence of desipramine, UK42620 but not tyramine produced a decrease in the stimulation-induced efflux of radioactivity that was antagonized by idazoxan. 5. Thus, UK42620 had prejunctional alpha(2)-adrenoceptor activity like that of clonidine- and tyramine-like activity releasing large amounts of noradrenaline.
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Thaina et al. (2001) studied this question. UK42620 vs. Tyramine was evaluated on Inotropic and chronotropic responses, and release of radioactivity. UK42620 produced positive inotropic and chronotropic responses and massive release of noradrenaline, exhibiting both tyramine-like and prejunctional alpha(2)-adrenoceptor activity.
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