Quantitative effects of nefiracetam on spatial learning of rats after cerebral embolism

Direct thrombin inhibitor argatroban reduces stroke damage in 2 different models

BACKGROUND AND PURPOSE

We showed previously robust neuroprotection with the thrombin inhibitor argatroban and now sought additional support for its neuroprotective potential.

METHODS

We used behavioral and histological end points; rigorously blinded the study groups; extended the treatment window to 3 hours after ischemia onset; and used 2 separate models. First, 2-hour filament middle cerebral artery occlusion in 64 male Sprague-Dawley rats was followed by learning and memory testing and quantitative histomorphometry. Randomly assigned treatment was 0.45 mg argatroban, saline, or 0.4 U thrombin. Second, we used the quantal bioassay (n=272) after 2-hour middle cerebral artery occlusion to detect the longest time delay after which therapy failed.

RESULTS

Argatroban powerfully and significantly reversed learning and memory deficits because of focal ischemia compared with saline or thrombin (P<0.03; ANOVA). Argatroban was significantly (P<0.05; t test with Bonferroni) protective when given immediately or after 1, 2, 3, but not 4 hours delay.

CONCLUSIONS

We obtained supportive evidence for argatroban protection of the neurovascular unit using behavioral and histological measurements at realistic therapeutic time windows.

Nefiracetam attenuates post-ischemic nonconvulsive seizures in rats and protects neuronal cell death induced by veratridine and glutamate

AIMS

Stroke patients are at a high risk of developing post-ischemic seizures and cognitive impairment. Nefiracetam (NEF), a pyrrolidone derivative, has been shown to possess both anti-epileptic and cognitive-enhancing properties. In this study the anti-seizure effects of NEF were evaluated in a rat model of post-ischemic nonconvulsive seizures (NCSs). Its potential mechanisms were investigated in neuronal cell culture assays of neurotoxicity associated with ischemic brain injury and epileptogenesis.

MAIN METHODS

In the in vivo study, rats received 24h permanent middle cerebral artery occlusion. NEF was administered intravenously either at 15 min post-injury but prior to the first NCS event (30 mg/kg, pre-NCS treatment) or immediately after the first NCS occurred (30 or 60 mg/kg, post-NCS treatment). In the in vitro study, neuronal cell cultures were exposed to veratridine or glutamate and treated with NEF (1-500 nM).

KEY FINDINGS

The NEF pre-NCS treatment significantly reduced the NCS frequency and duration, whereas the higher NEF dose (60 mg/kg) was required to achieve similar effects when given after NCS occurred. The NEF treatment also dose-dependently (5-500 nM) protected against neuronal cell death induced by veratridine as measured by MTT cell viability assay, but higher doses (250-500 nM) were required against glutamate toxicity.

SIGNIFICANCE

The anti-seizure property of NEF was demonstrated in a clinically relevant rat model of post-ischemic NCS. The preferential effects of NEF against in vitro veratridine toxicity suggest the involvement of its modulation of sodium channel malfunction. Future studies are warranted to study the mechanisms of NEF against ischemic brain injury and post-ischemic seizures.