Decreased hippocampal brain-derived neurotrophic factor and impaired cognitive function by hypoglossal nerve transection in rats

Neurocognitive effects of six ketamine infusions and the association with antidepressant effects in treatment-resistant bipolar depression: a preliminary study

Objective

The N-methyl-D-aspartate subtype glutamate receptor antagonist ketamine has rapid antidepressant and antisuicidal effects in treating treatment-resistant bipolar depression (TRBD). The neurocognitive effects of repeated ketamine infusions in TRBD are not known.

Methods

Six intravenous infusions of ketamine (0.5 mg/kg over 40 min) were administered on a Monday–Wednesday–Friday schedule during a 12-day period on 16 patients with TRBD followed by a 2-week observational period. The assessment of neurocognitive function was conducted using the MATRICS Consensus Cognitive Battery at baseline, 13 and 26 days. Tasks were designed to test speed of processing, working memory, visual learning and verbal learning.

Results

A significant improvement was found only in scores of speed of processing (F = 9.9, p = 0.001) after a 2-week observational period, which was accounted for by the improvement of depression symptoms. There were no significant changes over time in terms of working memory, visual learning and verbal learning. Pearson correlation analysis showed that the improvement of depression symptoms through six ketamine infusions was greater among TRBD patients with lower working memory at baseline (r = 0.54, p = 0.03). In multiple regression analysis, the significant correlation was still maintained (beta = 0.67, t = 2.2, p = 0.04).

Conclusion

This preliminary study indicated that six ketamine infusions were not harmful but were slightly beneficial for speed of processing in TRBD. However, this change was mainly accounted for the improvement of depression symptoms over time. Lower baseline working memory appears to be associated with greater antidepressant response after completion of six ketamine infusions in patients with TRBD.

Tadalafil restores long-term memory and synaptic plasticity in mice with hepatic encephalopathy

BACKGROUND AND AIM

Tadalafil displays important neuroprotective effects in experimental models of neurodegenerative diseases, however its mechanisms of action remain poorly understood. The aim of the present study was to investigate the action of Tadalafil on learning and memory, neuroinflammation, glial cell activation and neuroprotection in the experimental model of hepatic encephalopathy (HE) induced by Thioacetamide (TAA) in mice.

METHODS

Mice received intraperitoneal injections of TAA, for 3 consecutive days, reaching the final dose of 600 mg/kg. Tadalafil 15 mg/kg body weight was administered by gavage during 15 days after TAA induction. Mice underwent a Barnes maze for learning and memory evaluation.

RESULTS

Animals with hepatic encephalopathy showed reduced learning and spatial memory in the Barnes Maze, presented astrocyte and microglia activation and increased neuroinflammatory markers such as TNF-α, IL-1β, IL-6, p-p38, p-ERK and p-NF-kB. In addition, the signaling pathway PKA/PKG/CREB/BDNF/NeuN/synaptophysin and glutamate receptors were deregulated by TAA. Tadalafil treatment regulated the inflammation signaling pathways restoring learning and spatial memory.

CONCLUSION

Tadalafil significantly reduced neuroinflammation, promoted neuroprotection and plasticity, regulated the expression of hippocampal glutamate receptor and restored spatial learning ability and memory.

Umbilical Cord-Derived Mesenchymal Stromal Cells Contribute to Neuroprotection in Neonatal Cortical Neurons Damaged by Oxygen-Glucose Deprivation

Several studies have reported that human umbilical cord-derived mesenchymal stromal cells (UC-MSCs) restore neurological damage in vivo through their secretion of paracrine factors. We previously found that UC-MSCs attenuate brain injury by secreting neurotrophic factors, such as brain-derived neurotrophic factor (BDNF) and hepatocyte growth factor (HGF). However, how these factors contribute to neuroprotection remains unknown. In this study, we aimed to investigate to what extent UC-MSC-derived HGF and BDNF contribute to neuroprotection using a Transwell co-culture system of neonatal cortical neurons damaged by oxygen-glucose deprivation. The influence of HGF and BDNF were determined by investigating neurons in both the presence and absence of UC-MSCs as these cells consistently secrete both factors and can be blocked by neutralizing antibodies. In the co-culture, UC-MSCs significantly improved neuronal injury, as indicated by an increase in immature neuron number, neurite outgrowth, and cell proliferation. Co-culture of damaged neurons with UC-MSCs also exhibited a reduction in the number of neurons displaying signs of apoptosis/necrosis. The neuroprotective actions of UC-MSCs were partially reverted by neutralizing antibodies. Together, our findings reveal that UC-MSC-secreted HGF and BDNF have neuroprotective effects on damaged neurons. Further studies should address the existence of other potential neurotrophic paracrine factors.