Predicted cross-reactivity based on sequence identity: Mouse, Rat, Bovine.

Opioid is the term used to designate a group of compounds that are opium-like in their properties. These drugs have effects on perception of pain, consciousness, motor control, mood, and autonomic function, and can induce physical dependence. Pharmacologic studies suggested that there are at least 3 major classes of opioid receptors, designated delta, kappa, and mu. They differ in their affinity for various opioid ligands and in their cellular distribution. Studies of the receptors in the mouse and rat show that they are structurally related and are members of the family of 7 transmembrane-spanning G protein-coupled receptors.

Human and rat.

G protein-coupled receptors (GPCRs) are the largest family of membrane receptors that activate intracellular signaling cascades and undergo endocytosis, recycling, or degradation upon stimulation. The (mu), delta and kappa opioid receptors are GPCRs of the nervous system, which control pain, stress, and addictive behaviors. The kappa opioid receptor (KOR-1) plays a role in arousal and regulation of autonomic and neuroendocrine functions and is the receptor for dynorphins. KOR-1 inhibits neurotransmitter release by reducing calcium ion currents and increasing potassium ion conductance.