Table 1

Physiological effects of altering α₂-adrenergic receptor gene expression in mice

Physiological Effect	Genetic Alterations
Physiological Effect	α_2A-D79N	α_2A-KO	α_2B-KO	α_2C-KO
Hypotensive effects of α₂-adrenergic receptor agonist	X	X	↑	−
Bradycardic effects of α₂-adrenergic receptor agonist	↓	↓	−	−
Hypertensive effects of α₂-adrenergic receptor agonist	↓^1-a	−	X	−
Cardiovascular effects of imidazoline agonist	X
Resting heart rate	−	↑	−	−
Resting blood pressure	−	−	−	−
Salt-induced hypertension			X^1-b	−
Sedative effects of dexmedetomidine	X		−	−
Antinociceptive effects of α₂-adrenergic receptor agonist	X/↓^1-c		−	−
Antinociceptive effects of moxonidine	↓
Adrenergic-opioid synergy in spinal antinociception	X
Anesthetic-sparing effects of dexmedetomidine	X
Hypothermic effects of dexmedetomidine	X		−	−/↓
Antiepileptogenic effects of endogenous norepinephrine	X
Presynaptic inhibition of norepinephrine release	−	↓	−	↓^1-d
Autoinhibition of locus coeruleus	X

The α_2A-subtype mediates most of the classical effects of α₂-adrenergic receptor agonists.

X, abolished; −, no effect; ↑, accentuated; ↓, attenuated; and blank, not studied.
↵1-a Dependent on site of agonist administration.
↵1-b Mice were heterozygous (+/−) for α_2B-null mutation.
↵1-c Extent of attenuation depended on test used.
↵1-d In α_2AC-double KO mice.