The Binding of Donepezil with External Mouth of K+-Channels of Molluscan Neurons

Donepezil attenuated oxygen-glucose deprivation insult by blocking Kv2.1 potassium channels

Excessive K(+) efflux via activated voltage-gated K(+) channels (Kv channels) and the consequent intracellular K(+) depletion during and after ischemia/hypoxia induced long-lasting membrane depolarization promotes neuronal apoptosis. Although it has been suggested as an important potassium channel subtype in oxidative stress induced neuron apoptosis, whether Kv2.1 mediates ischemic apoptosis remains undefined. In the present study, the role of Kv2.1 played in hypoxia/anoxia induced cell apoptosis and correlated protective effect of donepezil were evaluated. Kv2.1 transfected HEK293 cell line (Kv2.1/HEK293) was used to study oxygen-glucose deprivation (OGD) induced cell apoptosis. We found Kv2.1 transfection increased the vulnerability of HEK293 cells to OGD insult, blocking Kv2.1 potassium channel by tetraethylammonium (TEA, 10mM) could attenuated OGD induced Kv2.1/HEK293 cell apoptosis significantly. OGD slightly reduced Kv2.1 currents without affecting channel kinetic activity. However, the membrane potential of Kv2.1/HEK293 cells depolarized to around 0mV after OGD treatment, a potential which could activated Kv2.1 persistently. Donepezil blocked Kv2.1 currents in a dose-dependent manner (IC(50)=7.59μM). Under OGD condition, donepezil (30μM) effectively inhibited Kv2.1 currents by accelerating channel inactivation and decreased Kv2.1/HEK293 cell apoptosis rate. In conclusion, our study revealed both the conducting role of Kv2.1 in OGD induced cell apoptosis and the importance of Kv2.1 as a target for neuronal protection. In addition, besides anti-acetylcholinesterase activity, Kv2.1 blockade capability of donepezil may attribute to its neuroprotective effects against ischemic apoptosis.

Enhanced dendritic spine number of neurons of the prefrontal cortex, hippocampus, and nucleus accumbens in old rats after chronic donepezil administration

In Alzheimer's disease brains, morphological changes in the dendrites of pyramidal neurons of the prefrontal cortex (PFC) and hippocampus have been observed. These changes are particularly reflected in the decrement of both the dendritic tree and spine number. Donepezil is a potent and selective acetylcholinesterase inhibitor used in the treatment of Alzheimer's disease. We have studied the effect of oral administration of this drug on the morphology of neuronal cells from the brain of aged rats. We examined dendrites of pyramidal neurons of the PFC, dorsal or ventral hippocampus (VH), and medium spiny neurons of the nucleus accumbens (NAcc). Donepezil (1 mg/kg, vo) was administrated every day for 60 days to rats aged 10 and 18 months. Dendritic morphology was studied by the Golgi-Cox stain procedure followed by Sholl analysis at 12 and 20 months ages, respectively. In all Donepezil-treated rats, a significant increment of the dendritic spines number in pyramidal neurons of the PFC and dorsal hippocampus was observed. However, pyramidal neurons of the VH and medium spiny cells of the NAcc only showed an increase in the number of their spines in 12-month-old rats. Our results suggest that Donepezil prevents the alterations of the neuronal dendrite morphology caused by aging.