European journal of pharmacology
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Agonists selectively acting at NOP, MOP, DOP and KOP receptors as well as mixed opioid receptor agonists are known to exert anti-hypersensitive efficacy in the rat spinal nerve ligation (SNL) model of neuropathic pain. To investigate the relative contribution of individual opioid receptor activation to the overall efficacy of mixed opioid receptor agonists, selective doses of respective opioid receptor antagonists have to be employed. ⋯ Selectivity could be demonstrated for MOP, DOP and NOP receptor antagonists, as they did not attenuate effects mediated by agonists acting on non-cognate receptors, whereas the KOP receptor antagonist nor-BNI demonstrated partial cross-antagonism of the DOP receptor agonist SNC-80. Thus, specific doses of opioid receptor antagonists that completely but still selectively attenuate full anti-hypersensitive efficacy of corresponding opioid receptor agonists were identified in the rat SNL model.
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Alzheimer's disease (AD) is a progressive neurodegenerative disorder for which there is no cure. The early primary symptom of AD is the decline of memory ability, which gradually develops into complete dementia. Type 2 diabetes mellitus (T2DM) is an important risk factor of AD; and mimetics of the incretin hormone GLP-1 developed to treat diabetes are being tested as a novel therapeutic strategy for AD. ⋯ We found that: (1) DA5-CH administration effectively improved working-memory and long-term spatial memory of 9-month-old AD mice in Y-maze and Morris water maze tests; (2) DA5-CH also reduced hippocampal amyloid senile plaques and phosphorylated tau protein levels; (3) DA5-CH basically reversed the deficits in hippocampal late-phase long-term potentiation; (4) DA5-CH up-regulated the levels of p-PI3K and p-AKT growth factor kinases and prevented excessive activation of p-GSK3β in the hippocampus of APP/PS1 mice. Therefore, the neuroprotection of DA5-CH in alleviating cognitive impairments and pathological damages might be associated with the improvement of hippocampal synaptic plasticity and activation of the PI3K/AKT signaling pathway. We propose that DA5-CH may be beneficial for the treatment of AD patients, especially those with T2DM or hyperglycemia.