The imidazoline receptor is the main receptor for clonidine and other imidazoline interactions. There are three types of imidazoline receptors: I1 receptor - mediates the sympathetic inhibition of imidazoline on lowering blood pressure (NISCH or IRAS, imidazoline receptor antiserum selection), I2 receptor - allosteric binding site of monoamine oxidase and is involved in pain regulation and neuroprotection, and I3 receptor - regulates insulin secretion of islet β cells. Activated I1-imidazoline receptors initiate hydrolysis of phosphatidylcholine to DAG. Elevated DAG levels in turn trigger the synthesis of the second messenger arachidonic acid and hypocotyl. In addition, the sodium-hydrogen reverse transporter is inhibited and the enzyme catecholamine synthesis is induced. The I1-imidazoline receptor can belong to the neurocytokine receptor family because its signaling pathway is similar to interleukin.