Neuropharmacology最新文献

Benzodiazepines (BZDs) are critical sedative, anticonvulsant, and anxiolytic drugs that potentiate inhibitory GABAergic neurotransmission. However, clinical utility is hampered by drug tolerance and a hyperexcitable withdrawal syndrome characterized by neuronal excitation/inhibition (E/I) imbalance. Although enhanced excitation is implicated in BZD tolerance, the homeostatic changes to glutamatergic receptors remain undefined. Here, we report the impact of chronic (7-day) BZD treatment on excitatory synapse and NMDA receptor (NMDAR) function, expression, and subcellular localization in cortical neurons. Chronic treatment with the BZD diazepam (DZP) resulted in an increase in NMDAR-mediated miniature excitatory postsynaptic currents (mEPSCs). Confocal imaging studies revealed a DZP-induced enrichment of GluN2B-containing NMDARs at functional synapses (expressing AMPA receptors, AMPARs) while GluN2B subunit expression was otherwise unaltered. Conversely, localization of GluN2A-containing NMDARs (GluN2A-NMDARs) to functional synapses was unchanged, while GluN2A-NMDAR total protein levels and surface accumulation were enhanced. Intriguingly, we demonstrate for the first time the BZD-induced enrichment and expansion of GluN2A-NMDAR coverage at silent (AMPAR-lacking) synapses. Finally, biochemical fractionation analysis of the translation elongation protein eEF2, known to control E/I balance, detected lower levels of deactivated, phosphorylated eEF2 in the synaptic fraction of DZP-treated neurons, indicative of enhanced local translation. Collectively, our findings suggest that chronic BZD treatment triggers compensatory mechanisms which 1) enhance NMDAR function via increased GluN2B-NMDARs at functional synapses, and 2) promote the expression, surface localization, and accumulation of GluN2A-NMDARs at silent synapses, augmenting the potential for further synaptic plasticity.

Methylphenidate (MPH) is widely used as the first-line pharmacological treatment for attention-deficit/hyperactivity disorder (ADHD). However, its misuse as a cognitive enhancer has been increasing worldwide. Despite the scientific advances in understanding the effects of MPH on the brain, its impact on the retina, which shares the same embryonic origin with the brain, remains poorly understood. In the present study, primary retinal neural cell cultures were exposed to MPH (0.1-1 mM) alone or to MPH after an inflammatory stimulus (lipopolysaccharide; LPS, 1 μg/ml). Additionally, male Wistar Kyoto rats (WKY, control rats) and Spontaneously Hypertensive rats (SHR, ADHD model) were orally treated with MPH (1.5 mg/kg/day, P28-57). MPH (0.1 mM) preserved retinal cell viability but induced oxidative stress through NOX2 and PI3K/AKT/DRP1 signaling activation and mitochondrial dysfunction. This was evidenced by a decrease in the mitochondria number, increased fragmentation, impaired membrane potential, reduced oxygen consumption rate, and shifted metabolism towards a glycolytic metabolic profile. Under an inflammatory environment, MPH enhanced antioxidant defenses, decreased oxidative stress and intracellular calcium levels, and improved mitochondrial structure and function. These contrasting effects were corroborated in animal studies, where MPH treatment reduced oxidative stress and improved mitochondrial function in the ADHD model, despite having detrimental effects in control rats. Our findings uncover a novel mechanism through which MPH affects retinal cells via NOX2/PI3K/AKT/DRP1 signaling and mitochondrial alterations. Moreover, MPH demonstrates a context-dependent effect, yielding detrimental outcomes under physiological conditions but beneficial effects in inflammatory settings. These results provide new insights into both MPH's therapeutic potential and misuse-associated risks.

Seizure-associated cognitive comorbidities can substantially reduce the quality of life in people with epilepsy. Neuroinflammation is an invariant feature of all chronic neurologic diseases, including epilepsy, and acute brain insults, including status epilepticus (SE). The generalized seizures of SE trigger a robust inflammatory response involving astrocytosis, erosion of the blood-brain barrier (BBB), activation of brain-resident microglia, and recruitment of blood-borne C-C chemokine receptor type 2 positive (CCR2+) monocytes into the brain. We have demonstrated that blocking monocyte recruitment into the brain via global Ccr2 knockout or systemic CCR2 antagonism with a small molecule alleviates multiple deleterious pathologies induced by SE, including BBB damage, microgliosis, and neuronal damage, following pilocarpine-induced SE. This study aimed to determine if fleeting CCR2 antagonism improves SE-associated cognitive impairments in the long term. Here, we show that brief antagonism of CCR2 after SE prevents the working memory deficit in the Y-maze and retention memory in the novel object recognition test, but does not attenuate anxiety-like behavior in the open field arena. Notably, CCR2 antagonism was neuroprotective in the cortex and the CA1 region of the hippocampus. Neuronal numbers in the CA1 hippocampus, but not the cortex, correlated with retention memory. Our results indicate that blood-borne monocytes are a viable therapeutic cellular target for preventing cognitive comorbidities and neurodegeneration associated with seizures.