Table 1.
Summary of α1-adrenoceptor subtype characteristics
| Receptor subtype | α1A | α1B | α1D |
|---|---|---|---|
| Functional responses |
Control of blood pressure; vasoconstriction; smooth muscle contraction |
Regulatory;
minor contractile role |
Control of blood pressure; vasoconstriction; smooth muscle contraction |
| Location (relative to innervation) | Junctional and non-junctional | Junctional (mainly?) | |
| Functional response (model systems) | Rat vas deferens contraction | Rat spleen contraction | Rat aorta contraction |
| Ligand-binding assay (other than transfected) | Rat submandibular gland | Rat spleen | (None) |
| Noradrenaline potency | Moderate | Moderate | High |
| Selective agonists | A61603 | / | / |
| Selective antagonists | RS 100329 | / | BMY 7378 |
| Sensitivity to CECa | + | ++ | + |
| Second messengers systems | Gq/11, PI turnover | Gq/11, PI turnover | Gq/11, PI turnover |
aCEC affects all subtypes
A 61603, (N-[5-(4,5-dihydro-1H-imidazol-2yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl]-methanesulfonamide); BMY 7378, (8-[2-(4-(2-methoxyphenyl) piperazin-1-yl)ethyl]-8-azaspiro[4,5]decane-7,9-dione); CEC, chloroethylclonidine; Gq/11, G-protein; PI, phosphoinositol