Kappa Opioid Receptor

Three types of opioid receptors have been cloned -- mu, delta, and kappa. Opioid receptors are seven transmembrane G-protein coupled receptors. They share a high degree of homology and are most divergent at the N- and C-termini. Activation of mu opioid receptors leads to a decrease in neuronal excitability.

Kappa Opioid Receptor (KOR) is a 45 kDa 7TM opioid receptor that is primarily expressed in the central nervous system and peripheral visceral pain sensory nerves. Following ligation by dynorphin peptides, KOR signaling induces analgesia, dysphoria, diuresis, and increased feeding desire. KOR also exerts neuroprotective and anti-inflammatory effects.

Image: KOR staining of paraffin embedded human brainstem (medulla) tissue. Tissue was stained using anti-mouse HRP-DAB (brown) and counterstained with hematoxylin (blue).