Brain research
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Dopamine plays an important role in regulating neuronal functions in the central nervous system by activating the specific G-protein coupled receptors. Both D1 and D2 dopamine receptors are extensively distributed in the retinal neurons. In the present study, we investigated the effects of D1 receptor signaling on outward K(+) currents in acutely isolated rat retinal ganglion cells (RGCs) by patch-clamp techniques. ⋯ Both protein kinase A (PKA) and calcium/calmodulin-dependent protein kinase II (CaMKII) signaling pathways were likely involved in the SKF81297-induced suppression of the K(+) currents since either Rp-cAMP (10 μM), a cAMP/PKA signaling inhibitor, or KN-93 (10 μM), a specific CaMKII inhibitor, eliminated the SKF81297 effect. In contrast, neither protein kinase C (PKC) nor mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling pathway seemed likely to be involved because both the PKC inhibitor bisindolylmaleimide IV (Bis IV) (10 μM) and the MAPK/ERK1/2 inhibitor U0126 (10 μM) did not block the SKF81297-induced suppression of the K(+) currents. These results suggest that activation of D1 receptors suppresses the Gb- and 4-AP-sensitive K(+) current components in rat RGCs through the intracellular PKA and CaMKII signaling pathways, thus modulating the RGC excitability.
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In addition to a prominent role in glycemic control, glucagon-like peptide 1 (GLP-1) receptor agonists exhibit neuroprotective properties. There is mounting experimental evidence that GLP-1 receptor agonists, including liraglutide, may enhance synaptic plasticity, counteract cognitive deficits and ameliorate neurodegenerative features in preclinical models of Alzheimer's disease (AD), predominantly in the context of β-amyloid toxicity. Here we characterized the effects of liraglutide in a transgenic mutant tau (hTauP301L) mouse tauopathy model, which develops age-dependent pathology-specific neuronal tau phosphorylation and neurofibrillary tangle formation with progressively compromised motor function (limb clasping). ⋯ Stereological analyses demonstrated that hTauP301L mice exhibited hindbrain-dominant neuronal accumulation of phosphorylated tau closely correlated to the severity of clasping behavior. In correspondence, liraglutide treatment significantly reduced neuronal phospho-tau load by 61.9±10.2% (p<0.001) in hTauP301L mice, as compared to vehicle-dosed controls. In conclusion, liraglutide significantly reduced tau pathology in a transgenic mouse tauopathy model.
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Spinal cord injury (SCI) often results in some form of paralysis. Recently, SCI therapy has been focused on preventing secondary injury to reduce both neuroinflammation and lesion size so that functional outcome after an SCI may be improved. Previous studies have shown that adenosine receptors (AR) are a major regulator of inflammation after an SCI. ⋯ The results showed that spontaneous functional recovery was blocked after the animals were subjected caffeine daily. Moreover, caffeine administration increased the demyelination area, promoted astrocyte and microglia activation and decreased the quantity of neurofilaments. These findings suggest that the neurotoxicity effect of caffeine may be associated with the inhibition of neural repair and the promotion of neuroinflammation.
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Hypoxia is a critical secondary injury mechanism in traumatic brain injury (TBI), and early intervention to alleviate post-TBI hypoxia may be beneficial. NVX-108, a dodecafluoropentane perfluorocarbon, was screened for its ability to increase brain tissue oxygen tension (PbtO2) when administered soon after TBI. ⋯ NVX-108 caused an increase in PbtO2 following CCI-TBI in rats and should be evaluated further as a possible immediate treatment for TBI.