Kappa Opioid Receptor Agonist Administration in Olfactory Bulbectomized Mice Restores Cognitive Impairment through Cholinergic Neuron Activation.

Olfactory bulbectomized (OBX) mice are characterized by impaired performance in the passive avoidance test and decreased number of cholinergic neurons in the hippocampus. Several studies have reported that κ-opioid receptor agonists improve cognitive function in mice. However, their influence on OBX-induced cognitive dysfunction remains unclear. To address this question, we evaluated the effects of the endogenous κ-opioid receptor agonist dynorphin A (Dyn A) and the selective agonist trans-(-)-U-50488 on the behavior of OBX mice in the passive avoidance test. The cognitive dysfunction of OBX mice was significantly recovered by the intracerebroventricular administration of Dyn A or trans-(-)-U-50488. The effects of these two agonists were counteracted by the selective κ-opioid receptor antagonist nor-binaltorphimine or the inhibitor of acetylcholine release β-bungarotoxin. These findings suggest that κ-opioid receptor agonists produce anti-dementia effects through activation of cholinergic neurons in OBX mice.