Ca<scp>MKII</scp> activity is essential for improvement of memory‐related behaviors by chronic rivastigmine treatment

Abstract

Abstract Because the cholinergic system is down‐regulated in the brain of Alzheimer's disease patients, cognitive deficits in Alzheimer's disease patients are significantly improved by rivastigmine treatment. To address the mechanism underlying rivastigmine‐induced memory improvements, we chronically treated olfactory bulbectomized ( OBX ) mice with rivastigmine. The chronic rivastigmine treatments for 12–13 days starting at 10 days after OBX operation significantly improved memory‐related behaviors assessed by Y‐maze task, novel object recognition task, passive avoidance task, and Barnes maze task, whereas the single rivastigmine treatment failed to improve the memory. Consistent with the improved memory‐related behaviors, long‐term potentiation in the hippocampal CA 1 region was markedly restored by rivastigmine treatments. In immunoblotting analyses, the reductions of calcium/calmodulin‐dependent protein kinase II (CaMKII) autophosphorylation and calcium/calmodulin‐dependent protein kinase IV (CaMKIV) phosphorylation in the CA1 region in OBX mice were significantly restored by rivastigmine treatments. In addition, phosphorylation of AMPAR subunit glutamate receptor 1 (GluA1) (Ser‐831) and cAMP‐responsive element‐binding protein (Ser‐133) as downstream targets of CaMKII and CaMKIV, respectively, in the CA 1 region was also significantly restored by chronic rivastigmine treatments. Finally, we confirmed that rivastigmine‐induced improvements of memory‐related behaviors and long‐term potentiation were not obtained in CaMKIIα +/− mice. On the other hand, CaMKIV −/− mice did not exhibit the cognitive impairments. Taken together, the stimulation of CaMKII activity in the hippocampus is essential for rivastigmine‐induced memory improvement in OBX mice. image We performed that whether chronic rivastigmine treatments improve hippocampal LTP in CA1 from CaMKIIα +/− mice. Rivastigmine treatments failed to improve LTP in CA1. In immunoblotting analysis, rivastigmine did not affect autophosphorylation of CaMKIIα (Thr‐286) in CA1. Lack of rivastigmine effects in CaMKIIα +/− mice confirms that stimulation of CaMKII activity was critical for the rivastigmine‐induced memory improvement.