Cirazoline is a nonselective agonist

Agonist

An agonist is a chemical that binds to a receptor of a cell and triggers a response by that cell. Agonists often mimic the action of a naturally occurring substance...

 of the alpha-1 adrenergic receptor

Alpha-1 adrenergic receptor

The alpha-1 adrenergic receptor is a G protein-coupled receptor associated with the Gq heterotrimeric G-protein. It consists of three highly homologous subtypes, including α1A-, α1B-, and α1D-adrenergic...

 (α1-AR), and an antagonist

Antagonist

An antagonist is a character, group of characters, or institution, that represents the opposition against which the protagonist must contend...

 to the alpha-2 adrenergic receptor

Alpha-2 adrenergic receptor

The alpha-2 adrenergic receptor is a G protein-coupled receptor associated with the Gi heterotrimeric G-protein. It consists of three highly homologous subtypes, including α2A-, α2B-, and α2C-adrenergic. Some species other than humans express a fourth α2D-adrenergic receptor as well...

. It is believed that this combination of properties could make cirazoline an effective vasoconstricting agent.

Cirazoline has also been shown to decrease food intake in rats, purportedly through activation of alpha 1-adrenoceptors in the paraventricular nucleus

Paraventricular nucleus

The paraventricular nucleus is a neuronal nucleus in the hypothalamus. It contains multiple subpopulations of neurons that are activated by a variety of stressful and/or physiological changes. Many PVN neurons project directly to the posterior pituitary where they release oxytocin or vasopressin...

in the hypothalamus of the brain.