Objective To characterize the function of a new xanomeline-derived M 1 agonist, 3-[3-（3-florophenyl-2-propyn- 1- ylthio）-1,2,5-thiadiazol-4-yl]-1,2,5,6- tetrahydro-1-methylpyridine Oxalate （EUK1001）, the acute toxicity and the effects on synaptic plasticity and cognition of EUK1001 were evaluated. Methods To examine the median lethal dose （LD50） of EUK1001, a wide dose range of EUK1001 was administered by p.o. and i.p. in aged mice. Furthermore, novel object recognition task and in vitro electrophysiological technique were utilized to investigate the effects of EUK1001 on recognition memory and hippocampal synaptic plasticity in aged mice. Results EUK1001 exhibited lower toxicity than xanomeline, and improved the performance of aged mice in the novel object recognition test. In addition, bath application of 1 μmol/L EUK1001 directly induced long-term potentiation in the hippocampus slices. Conclusion We conclude that EUK1001 can improve the agerelated cognitive deficits.
Objective To explore the role of the extracellular signal-regulated kinase （ERK）/cAMP response element binding protein （CREB） pathway in the induction of long-term potentiation （LTP） in the anterior cingulate cortex （ACC） that may be implicated in pain-related negative emotion. Methods LTP of field potential was recorded in ACC slice and the expressions of phospho-ERK （pERK） and phospho-CREB （pCREB） were examined using immunohistochemistry method. Results LTP could be induced stably in ACC slice by high frequency stimulation （2-train, 100 Hz, 1 s）, while APv （an antagonist of NMDA receptor） could block the induction of LTP in the ACC, indicating that LTP in this experiment was NMDA receptor-dependent. Bath application of PD98059 （50 μmol/L）, a selective MEK inhibitor, at 30 min before tetanic stimulation could completely block the induction of LTP. Moreover, the protein level of pERK in the ACC was transiently increased after LTP induction, starting at 5 rain and returning to basal at 1 h after tetanic stimulation. The protein level of pCREB was also increased after LTP induction. The up-regulation in pERK and pCREB expressions could be blocked by pretreatment of PD98059. Double immunostaining showed that after LTP induction, most pERK was co-localized with pCREB. Conclusion NMDA receptor and ERK-CREB pathway are necessary for the induction of LTP in rat ACC and may play important roles in pain emotion.
