Dynorphin A (1-10) an endogenous opioid neuropeptide, binds to extracellular loop 2 of the κ-opioid receptor. Dynorphin A (1-10) also blocks NMDA-activated current with an IC50 of 42.0 μM. κ-opioid receptor[1]NMDA receptor[2]

Dynorphin A (1-10) binds in the transmembrane domain of the κ-receptor[1]. The non-opioid actions of various forms of Dynorphin A (DynA) are examined on N-methyl-D-aspartate (NMDA) receptor channels in isolated rat trigeminal neurons using the whole-cell patch recording technique. All the dynorphins tested blocked NMDA-activated currents. The blocking actions are voltage-independent. The IC50 is 42.0 μM for DynA(1-10). To determine if shorter dynorphins have the similar blocking property, we examined the action of DynA(1-10) at different membrane potentials. DynA(1-10) blocks INMDA to a similar extent as the membrane potentials changed from -80 to +60 mV. Thus, despite a 160-fold difference in the apparent affinities, DynA(1-32) and DynA(1-10) both exert voltage-independent actions on NMDA receptors[2].

[1]. Paterlini G, et al. Molecular simulation of dynorphin A-(1-10) binding to extracellular loop 2 of the kappa-opioidreceptor. A model for receptor activation. J Med Chem. 1997 Sep 26;40(20):3254-62. [2]. Chen L, et al. Dynorphin block of N-methyl-D-aspartate channels increases with the peptide length. J Pharmacol Exp Ther. 1998 Mar;284(3):826-31.