Distribution of Receptors and Characteristic Responses Mediated by Adrenoceptors
Distribution of receptors:
Adrenergically innervated organs and tissues tend to have a predominance of one type of receptor.
1 tissues such as the vasculature to skeletal muscle have both α1 and β2 receptors,
but the β2 receptors predominate.
Other tissues may have one type of receptor exclusively, with practically no signif cant numbers of other types of adrenergic receptors.
- 2 the heart contains
- predominantly β1 receptors.
4. Characteristic responses mediated by adrenoceptors:
It is use-ful to organize the physiologic responses to adrenergic stimulation according to receptor type,
because many drugs preferentially stim-ulate or block one type of receptor.
Figure 6.6 summarizes the most prominent ef ects mediated by the adrenoceptors.
As a generaliza-tion,
1 stimulation of α1 receptors characteristically produces
vasocon-striction (particularly in skin and abdominal viscera)
and an increase in total peripheral resistance
and blood pressure.
Conversely, stimu-lation of β1 receptors characteristically causes
whereas stimulation of β2 receptors produces
vasodilation (in skel-etal vascular beds) and