Table 2

Pharmacological characterization of α2-adrenoceptor subtypes

α2A2-aα2Bα2C
Potency orderadrenaline > noradrenaline
Selective agonistsOxymetazoline2-b
Selective antagonistsBRL 44408 (8.0)ARC 239 (8.0)ARC 239 (8.0)
Prazosin (7.5)Prazosin (7.5)
Imiloxan (7.3)
  • Antagonist affinities (number in parentheses) are expressed as approximate −log K i values. Adapted from Alexander and Peters (1999).

  • 2-a α2A-adrenoceptors from rats, mice, and cows have a ≈20-fold lower affinity for yohimbine, rauwolscine, and oxymetazoline than do their human orthologs.

  • 2-b Reduced efficacy agonist.