2), much higher than that observed when the two compounds were administered separately. Figure 2 Protective effects afforded by combined treatments with memantine, ifenprodil, and galantamine

against NMDA neurotoxicity in cultured rat cortical neurons. Treatment with galantamine (1 μmol/L)/memantine (0.1 μmol/L) or galantamine (1 … Galantamine exerts its neuroprotective effect via α7 and α4β2 nicotinic acetylcholine receptors Galantamine does not bind to NMDARs (Simoni et al. 2012). Therefore, the reported effect against the NMDA-induced toxicity cannot be ascribed to the inhibition of these receptors. Galantamine increases Inhibitors,research,lifescience,medical ACh concentration via inhibition of AChE. Inhibitors,research,lifescience,medical In addition, it has been reported that galantamine is an allosteric modulator of nAChRs (Maelicke and Albuquerque 2000; Samochocki et al. 2003). Therefore, we assessed the role of nAChRs by blocking the α7 and α4β2 nAChRs, which are the most affected nAChRs subtypes in AD. Administration of MCC, an α7 nAChR antagonist, partially blocked the neuroprotective effect of galantamine (5 μmol/L) in a concentration-dependent manner, reaching a maximal effect at 10 nmol/L (Fig. 3A). Similarly, DHBE, an α4β2 nAChR antagonist, attenuated

the protective effect of galantamine, although to a lesser extent than did MCC (Fig. 3B). To further test the possible role of α7 nAChR, we evaluated the effect of the α7 agonist ARR in directly potentiating the Inhibitors,research,lifescience,medical neuroprotective effect Inhibitors,research,lifescience,medical of memantine or ifenprodil (Fig. 3C). Our data show that ARR potentiated the effect of both memantine and ifenprodil, although to a lesser extent when compared with galantamine. Figure 3 Blockade of α7 or α4β2 nAChRs decreases

galantamine neuroprotection against NMDA toxicity, and activation of α7 nAChR with memantine or ifenprodil shows neuroprotective effect. Exposure Inhibitors,research,lifescience,medical of neuronal cultures to different … Finally, we treated cells with the memantine/galantamine combination and then with MCC and/or DHBE. Our results revealed a decreased potentiating effect of galantamine with either MCC or DHBE (Fig. 4A). When the two compounds were given simultaneously, the protective effect of the memantine/galantamine Anacetrapib combination was completely lost. These experiments were repeated with the ifenprodil/galantamine combination, obtaining similar results (Fig. 4B). Discussion Overactivation of NMDARs leads to neuronal death in different neurodegenerative conditions, including AD (Chen and Lipton 2006). Our results confirm previous data indicating that memantine prevents NMDA-induced excitotoxicity in rat neuronal cultures (Chen et al. 1992; Volbracht et al. 2006). Recent studies have suggested that memantine could preferentially block the extrasynaptic NMDARs, leaving untouched the synaptic receptors (Xia et al. 2010). It has been reported that extrasynaptic NMDARs are enriched of NR2B subunits (Thomas et al. 2006).