TABLE 1

Summary of the pharmacological effects mediated by imidazoline receptors

Receptor Type	Common Ligands	Pharmacological Effects
Receptor Type	Common Ligands	Cellular Effect	Cellular Action	In Vivo Effect	In Vivo Action
I₁	LNP509, LNP599, LNP91, LNP911	Cell viability	Is antiproliferative; protects cell viability	Blood pressure	Reduces blood pressure and heart rate
		Insulin and adiponectin	Stimulates the secretion of adiponectin; increases insulin sensitivity; is insulinotropic	Heart arrhythmia	Has an antiarrhythmic effect
		Neurons	Increases MAPK activity; decreases GABA_A receptor–mediated inhibitory postsynaptic currents	Heart failure	Improves cardiac performance in congestive heart failure; prevents ventral hypertrophy
				Glucose and lipid metabolism	Reduces insulin resistance, hyperinsulinemia, hypertension, and metabolic syndrome
I₂	2-BFI, BU224, CR4056, tracizoline, idazoxan, phenyzoline			Pain	Is antinociceptive in multiple models of chronic pain; enhances the antinociceptive effects of opioids; reduces antinociceptive tolerance and physical dependence of opioids
				Subjective effects	Produces characteristic discriminative stimulus effects specific to I₂ receptor activation
				Neuroprotection	Is neuroprotective in a rat cerebral ischemia model
				Body temperature	Reduces body temperature and may involve temperature regulation
I₃	KU-14R	Insulin secretion	Facilitates insulin secretion