Key points are not available for this paper at this time.
In 1948 Ahlquist suggested that there were two types of catechol amine receptor, which he designated a and 8. The first compound shown to block selectively the ,8-receptors was dichloroisoprenaline They also found that dichloroisoprenaline itself increased heart rate and cardiac contractile force and reduced arterial pressure. These effects were attributed to a sympathomimetic action, which has been demonstrated in isolated heart preparations, conscious and anaesthetized animals and in man (Furchgott, 1959; Black Glover, Greenfield & Shanks, 1962). Recent studies suggest that pronethalol may possess intrinsic sympathomimetic activity, but to a much lesser extent than dichloroisoprenaline. Donald, Kvale & Shepherd (1964) found that in anaesthetized dogs pronethalol increased cardiac output and stroke volume, and in conscious dogs with cardiac denervation it increased heart rate. In all dogs there was a fall in arterial pressure. Similar results were obtained in anaesthetized dogs by
R.G. Shanks (1966) studied this question.