α-adrenergic receptors and pacemaker current in cardiac Purkinje fibres

IN recent years, membrane phenomena in cardiac fibres have been analysed with increasing accuracy, by the use of electronic feedback. Ionic transmembrane currents have now been measured and analysed for their rectifier properties, their time constants and their activation ranges. One of the current components analysed in much detail is the pacemaker current in cardiac Purkinje fibres. Evidence is now accumulating that this and other current systems are related to adrenergic receptors. Strong evidence has been put forward that this current is dependent on β-adrenergic receptors. In this paper we report results of tests carried out to investigate the involvement of α-adrenoceptors in controlling this process and to show that they are not directly involved.