Protective effect of DM-9384, a novel pyrrolidone derivative, against experimental cerebral anoxia

Single- and Multiple-dose Pharmacokinetics of Nefiracetam, a New Nootropic Agent, in Healthy Volunteers

The pharmacokinetic profile of nefiracetam (N-(2,6-dimethylphenyl)-2-(2-oxo-l-pyrrolidinyl)acetamide), a new nootropic agent, was studied in healthy Japanese male volunteers. Nefiracetam was administered orally at doses of 10–200 mg in the single-dose studies, and at doses of 200 mg three times a day for seven days in the multiple-dose study. An HPLC method was used to determine the concentrations of nefiracetam in serum, urine and faecal samples. Linear kinetic behaviour was obtained after single oral administration. Serum concentrations of nefiracetam reached maximum values (Cmax) within 2 h for all dosage groups, and declined monophasically after Cmax with half-lives of 3–5 h. The area under the concentration-time curve (ALTC∞) and Cmax were linearly related to the dose. The apparent clearance (CL) values were 94·4–140·3 mL min−1. Urinary excretion of nefiracetam was independent of the administered dose, and less than 10% of the dose was recovered in urine as the unchanged form within 24 h after administration. Renal clearance (CLR) did not change significantly as dose increased from 10 to 1200 mg. Faecal excretion of nefiracetam was less than 0·1% of the dose up to 24 h after a 300 mg oral dose. Food intake delayed the absorption of nefiracetam but did not significantly modify its pharmacokinetics. No clinically significant accumulation of nefiracetam in the body was observed during and after multiple doses.

Cerebral protective and cognition-improving effects of sinapic acid in rodents

We previously demonstrated that tenuifoliside B and 3,6'-disinapoylsucrose in Polygalae Radix, the root of Polygala tenuifolia WILLDENOW, inhibited potassium cyanide (KCN)-induced hypoxia and scopolamine-induced memory impairment in mice. Because both ingredients have a common sinapoyl moiety in their structure, we inferred that the sinapoyl moiety could inhibit hypoxia and memory impairment. In the present study to clarify the hypothesis, sinapic acid inhibited KCN-induced hypoxia and scopolamine-induced memory impairment as well as tenuifoliside B and 3,6'-disinapoylsucrose did. In addition, sinapic acid inhibited decompression- or bilateral carotid artery ligation-induced hypoxia (or mortality) and CO2-induced impairment in mice, and basal forebrain lesion-induced cerebral cholinergic dysfunction (decreases in acetylcholine concentration and choline acetyltransferase activity) in rats. These results, taken together, suggest the possibilities that sinapic acid is not only a very important moiety in the pharmacological activities of tenuifoliside B and 3,6'-disinapoylsucrose but also a candidate for a cerebral protective and cognition-improving medicine.

Cognitive Improving and Cerebral Protective Effects of Acylated Oligosaccharides in Polygala tenuifolia

We studied the cognitive improving and cerebral protective constituents in the roots of Polygala tenuifolia Willdenow, a well-known Chinese traditional medicine prescribed for amnesia, neurasthenia, palpitation, noctural emission and insomnia. Tenuifoliside B (1), which is one of the acylated oligosaccharides in the roots of P. tenuifolia, showed the cerebral protective effect on potassium cyanide (KCN)-induced anoxia in mice, widely used as an animal model for cerebrovascular disease, and also had an ameliorative effect on the scopolamine-induced impairment of performance in passive avoidance task in rats. Compound 1 significantly enhanced oxotremorine-induced tremors in mice, suggesting that it ameliorated the scopolamine-induced impairment of passive avoidance response by enhancing the cholinergic system. These findings show that compound 1 has cognitive improving and cerebral protective effects.

Antiepileptic effect of nefiracetam on kainic acid-induced limbic seizure in rats

Nefiracetam is being studied as a novel cognition-enhancing agent; however, it has been suggested from studying its chemical structure that it has a potential anticonvulsive effect. We examined the antiepileptic effect of nefiracetam on kainic acid (KA)-induced seizures. KA was infused into the left basolateral amygdaloid nucleus and focal limbic seizures were induced in 43 male Wistar rats. During status epilepticus, 10, 50, 100 or 200 mg/kg of nefiracetam was intravenously injected. Nefiracetam inhibited KA-induced limbic seizures at doses over 100 mg/kg while it had a sedative effect on the animals. In (14C) deoxyglucose autoradiographic studies, the propagation of seizure-induced hypermetabolic areas was also suppressed dose-dependently. From the results, it was indicated that nefiracetam has an antiepileptic effect and that its application may suppress seizure propagation. Further study is required, whether this agent is available as a novel anticonvulsant.

Electric field distribution of event-related potentials in stroke patients

Electrical field distributions of event-related potentials (ERP's) were recorded during an auditory "oddball paradigm" and were analyzed in terms of time and space. Fourteen normal subjects and 14 chronic patients were cerebral thrombosis were studied. For the components N1 and P3 of the ERP's to target stimuli, reference-independent measures (latency, global field power, location of maximal or minimal potential, and location of centroids) were determined. Stroke patients displayed P3 abnormalities in latency, amplitude, and electrical field on the scalp. In addition, N1 electrical fields were also abnormal. These ERP abnormalities correlated significantly with the extent of mental function impairment in the stroke patients, and they improved after administration of a cerebral metabolic enhancer (Nefiracetam: DM-9384). The ERP's seemed to be sensitive in indicating the effects of the drug. These data suggest that time-course analysis of the spatial distribution of the ERP electrical field might be useful for evaluation of the extent of mental function impairment and the efficacy of drugs.

Piracetam and other structurally related nootropics

Nearly three decades have now passed since the discovery of the piracetam-like nootropics, compounds which exhibit cognition-enhancing properties, but for which no commonly accepted mechanism of action has been established. This review covers clinical, pharmacokinetic, biochemical and behavioural results presented in the literature from 1965 through 1992 (407 references) of piracetam, oxiracetam, pramiracetam, etiracetam, nefiracetam, aniracetam and rolziracetam and their structural analogues. The piracetam-like nootropics are capable of achieving reversal of amnesia induced by, e.g., scopolamine, electroconvulsive shock and hypoxia. Protection against barbiturate intoxication is observed and some benefit in clinical studies with patients suffering from mild to moderate degrees of dementia has been demonstrated. No affinity for the alpha 1-, alpha 2-, beta-, muscarinic, 5-hydroxytryptamine-, dopamine, adenosine-A1-, mu-opiate, gamma-aminobutyric acid (GABA) (except for nefiracetam (GABAA)), benzodiazepine and glutamate receptors has been found. The racetams possess a very low toxicity and lack serious side effects. Increased turnover of different neurotransmitters has been observed as well as other biochemical findings, e.g., inhibition of enzymes such as prolylendopeptidase. So far, no generally accepted mechanism of action has, however, emerged. We believe that the effect of the racetams is due to a potentiation of already present neurotransmission and that much evidence points in the direction of a modulated ion flux by, e.g., potentiated calcium influx through non-L-type voltage-dependent calcium channels, potentiated sodium influx through alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor gated channels or voltage-dependent channels or decreases in potassium efflux. Effects on carrier mediated ion transport are also possible.

Nefiracetam (DM-9384) preserves hippocampal neural cell adhesion molecule-mediated memory consolidation processes during scopolamine disruption of passive avoidance training in the rat

Scopolamine (0.15 mg/kg), a muscarinic antagonist, when administered during training or at a discrete 6-h posttraining time point, is demonstrated to inhibit the recall of a step-down passive avoidance response when tested at 24 and 48 h after task acquisition. Nefiracetam (3 mg/kg), a piracetam-related nootropic, when given with scopolamine during training tended to improve task recall, and this effect was more pronounced when given at the 6-h posttraining time. Co-administration of nefiracetam with scopolamine was not necessary to achieve the antiamnesic action, as nefiracetam given during training significantly improved the memory deficits produced by scopolamine at the 6-h posttraining time. The paradigm-specific increase in hippocampal neural cell adhesion molecule sialylation, which is observed during consolidation of a passive avoidance response, was attenuated by the presence of scopolamine during training and at the 6-h posttraining time, and this effect was reversed by co-administration of nefiracetam, albeit in a paradigm-independent manner. These results suggest nefiracetam exerts a neurotrophic action that protects memory consolidation from drug interventive insults.

Effects of BMY-21502 on anoxia in mice

The protective effects of BMY-21502 (1-[[1-[2-(trifluoromethyl)-4-pyrimidinyl]-4-piperidinyl]methyl]-2- pyrrolidinone) against cerebral anoxia were investigated using various models in mice, in comparison with those of other cerebroactive drugs. Oral administration of BMY-21502 (10-100 mg/kg) significantly prolonged the survival time in KCN (2.4 mg/kg, i.v.)-induced anoxia. Oxiracetam and idebenone exerted similar but weak protection at doses above 100 mg/kg, p.o. and only at a dose of 100 mg/kg, p.o., respectively. Significant protection by BMY-21502 against moderate hypobaric hypoxia was observed at doses of 30 and 100 mg/kg, p.o. Idebenone (100 and 300 mg/kg, p.o.) significantly prolonged the survival time of mice in this model, but oxiracetam (30-300 mg/kg, p.o.) did not. Oral administration of all of these drugs (BMY-21502, 3-300 mg/kg; Oxiracetam, 100-1000 mg/kg; Idebenone, 100-1000 mg/kg) failed to increase the number of gasps and the duration of gasping in the decapitated head of mice as a complete ischemic model. The anti-anoxic effect of BMY-21502 in the KCN-anoxia model was blocked by pretreatment with scopolamine. These findings suggest that BMY-21502 has an anti-anoxic action superior to those of the other cerebroactive drugs used, and activation of the CNS cholinergic system is involved as one of the causative mechanisms for the anti-anoxic effect of BMY-21502.

Pharmacokinetics of nefiracetam and three metabolites in humans and stereoselective hydroxylation of its pyrrolidine ring

1. The kinetics of nefiracetam (I) and three metabolites (II-IV) were investigated in healthy volunteers. Compounds I-IV in serum and urine were measured by h.p.l.c. 2. After a single 200 mg dose of nefiracetam the drug was absorbed rapidly and showed peak serum levels of 16.3 +/- 0.9 nmol/ml. Cmax values of the three metabolites were comparatively low (0.96-4.89 nmol/ml), and tmax and t1/2 values of the metabolites (4.1-9.6 h and 7.8-21.9 h, respectively) were longer than those of I (1.6 h and 3.9 h respectively). Urinary excretion of I in 24 h was about 5% of the dose. The major urinary metabolite, a pyrrolidine ring scission product (IV), had a mean total excretion of 17.8% dose. The total of all four compounds in urine amounted to 43.4% dose. 3. In a multiple-dose study (daily 3 x 200 mg doses of nefiracetam for 7 days), the serum concentration profile of each compound indicated that the steady state was reached in 7 days. 4. Metabolite II existed as a racemate and III mainly as the (-)-enantiomer in human urine.

Involvement of the cholinergic system in the effects of nefiracetam (DM-9384) on carbon monoxide (CO)-induced acute and delayed amnesia

The effects of N-(2,6-dimethylphenyl)-2-(2-oxo-1-pyrrolidinyl)-acetamide (DM-9384, nefiracetam), a cyclic derivative of GABA, were investigated in the carbon monoxide (CO)-induced amnesia model in mice using the passive avoidance task. Memory deficiency occurred when mice were exposed to CO before memory was completely consolidated after training (acute amnesia), at 7 days before training and 7 days after training (delayed amnesia). DM-9384 prolonged the step-down latency in mice with CO-induced amnesia. Scopolamine blocked the anti-amnesic effect of DM-9384 on delayed amnesia that had been induced by pre- or post-training exposure to CO. Bicuculline had a tendency to antagonize the anti-amnesic effect of DM-9384, but this tendency was not significant. Under these conditions, no significant change in the activity of choline acetyltransferase and glutamic acid decarboxylase was observed in the frontal cortex, striatum and hippocampus. These results suggest that DM-9384 potentiates cholinergic neuronal function and that it may modify acquisition and/or consolidation of memory.

Effects of DM-9384, a pyrrolidone derivative, on ischemia-induced changes in the central monoamine systems

Alterations in brain tissue levels of monoamines and monoamine metabolites were studied in gerbils 60 min after cerebral ischemia induced by 10 min carotid ligation after pretreatment with the antiischemic drug DM-9384 (1, 3, 10, 30 mg/kg, PO). The DA levels decreased in striatum after the ischemia, while cortical and hippocampal DA levels increased. The DOPAC levels increased in cortex, but were essentially unaffected in other regions. The HVA levels increased in all forebrain regions studied. NA levels decreased in hippocampus and superior colliculus, while a general increase in MHPG levels was seen. Decreases in 5-HT levels were seen in all forebrain regions except cortex. The 10 mg/kg and 30 mg/kg doses of DM-9384 counteracted the decrease in striatal 5-HT and hypothalamic MHPG/NA ratio, respectively. Thus pretreatment with DM-9384 exerted minor protective effects on the alterations induced in monoamine systems by transient forebrain ischemia.