The roles of α 1A -a nd α 1B -adrenergic receptors in heart: insights from studies of genetically modified mice

Summary 1. An umber of mouse strains have been prepared in which different subtypes of the α 1 -adrenergic receptor (α 1 -AR) are overexpressed or deleted. The phenotypes of the animals generated vary depending on whether the receptors are expressed specifically in heart or generally throughout the animal, but some overall conclusions can be drawn. 2. Heightened activity of α 1B -ARs by overexpressing the receptors leads to depressed contractile responses to β-AR activation, which may be related to acti vation of the inhibitory G protein, Gi. In contrast, α 1A -AR cause substantially heightened contractility when o verexpressed