NK 2 receptor
Neurokinin A (NKA) and its truncated form NKA(4-10) are potent spasmogens of human colon circular muscle, an action mediated exclusively via tachykinin NK 2 receptors. A structure-activity study of the neurokinin A (NKA) fragment NKA(4-10) is performed to investigate the importance of amino acid residues for receptor efficacy, potency and affinity at the NK 2 receptor in human colon circular muscle. A high density of NK 2 receptors has been demonstrated in this tissue, using in vitro autoradiography and radioligand binding.