Effect of Piracetam, Vinpocetine and Ginkgo Biloba Extract on Antipsychotic-Induced Impairment of Learning and Memory

České info

Účinnost piracetamu, vinpocetinu a Ginkgo biloba na poruchy učení a paměti vyvolané antipsychotiky.

Haloperidol je klasické neuroleptikum, které vyvolává motorické abnormity a poruchy učení.

Cíl studie:
Zhodnotit schopnost nootropik piracetamu, vinpocetinu a Ginkgo biloba zlepšit prostorovou paměť myší léčených haloperidolem.

Metodologie:
Prostorová paměť byla hodnocena v Morrisově vodním bludišti (Morris water maze, MWM). Měřena byla účinnost piracetamu (50, 150 nebo 300 mg/ kg i.p.), vinpocetinu (1, 2 nebo 4 mg/ kg) nebo Ginkgo biloba (25, 50 nebo 150 mg/ kg) na pracovní paměť myší léčených haloperidolem (2 mg/ kg, i.p.) podávaným k vyvolání kognitivní poruchy [25]. Léčivé látky byly buď podávány současně s haloperidolem, nebo 30 minut před podáním haloperidolu.

Výsledky:
Podání haloperidolu vedlo k významnému prodloužení latence při hledání ponořené plošiny. Piracetam podaný současně s haloperidolem nebo 30 min před antipsychotikem zkracoval v závislosti na dávce latenci při hledání ponořené plošiny. Vinpocetin podaný současně s haloperidolem kognitivní výkon nezlepšil, ale vinpocetin 4 mg/ kg podaný 30 min před haloperidolem výrazně zkrátil latence při hledání ponořené plošiny. U myší léčených Ginkgo biloba došlo ke zhoršení výkonu ve vodním bludišti.

Závěr:
Piracetam a vinpocetin, avšak nikoli Ginkgo biloba, zlepšují poruchy učení a paměti vyvolané haloperidolem v Morrisově vodním bludišti. K potvrzení případné užitečnosti piracetamu a vinpocetinu při zlepšování kognice u pacientů léčených klasickými antipsychotiky je zapotřebí provést studie na lidských jedincích.

Klíčová slova:
prostorová paměť – haloperidol – nootropika – myši

Authors: Omar M. E. Abdel-Salam ^1,2; Somaia A. Nada ¹
Authors place of work: National Research Centre, Cairo, Egypt Department of Pharmacology ¹; National Research Centre, Cairo, Egypt Toxicology and Narcotics ²
Published in the journal: Cesk Slov Neurol N 2011; 74/107(1): 29-35
Category: Původní práce

Summary

Haloperidol is a classic neuroleptic drug with the known drawback that it induces motor abnormalities and impaired learning.

Aim:
To investigate the nootropic drugs piracetam, vinpocetine and extract of Ginkgo biloba for their ability to improve spatial memory in mice treated with haloperidol.

Methods:
Spatial memory was assessed by means of the Morris water maze (MWM) test. The effects of piracetam (50, 150 or 300 mg/ kg, i.p.), vinpocetine (1, 2 or 4 mg/ kg) and Ginkgo biloba extract (25, 50 or 150 mg/ kg) were studied on working memory in mice treated with haloperidol (2 mg/ kg, i.p.) to induce cognitive impairment [25]. The drugs were either co-administered with haloperidol or given 30 min before haloperidol administration.

Results:
The administration of haloperidol resulted in a significant increase in the time taken to locate a submerged test platform (latency). The time taken to locate the submerged platform was reduced dose-dependently by piracetam co-administered with haloperidol or given 30 min prior to the antipsychotic drug. Vinpocetine co-administered with haloperidol failed to improve cognitive performance, but vinpocetine at 4 mg/ kg administered 30 min before haloperidol markedly reduced the time to locate the submerged platform. Mice treated with Ginkgo biloba extract showed worsening of their performance on the water maze test.

Conclusion:
Piracetam and vinpocetine, but not Ginkgo biloba extract, alleviate haloperidol-induced impairment of learning and memory in the MWM test. Human studies are needed to establish whether piracetam as well as vinpocetine may prove of value in improving cognition in patients treated with classic antipsychotic drugs.

Key words:
spatial memory – haloperidol – nootropics – mice

Introduction

Memory, or the retention of learned information, is fundamental to human beings. Memory impairment such as that occurring in normal aging or in pathological conditions, e. g. Alzheimer’s disease, is a serious medical and social problem. At present, few drugs are available for the treatment of memory disorders. These include the pyrrilodine derivative piracetam [1], the synthetic vincamine derivative vinpocetine [2] and standardized extracts of Ginkgo biloba leaves [3]. Although these drugs belong to distinct and different chemical classes, they share the term “nootropic”, introduced by Giurgea in 1973 [4], to indicate a category of drugs that enhances memory, facilitates learning and protects memory processes against conditions that tend to disrupt them.

Piracetam, a pyrrilodine derivative (2-oxo-1-pyrrolidine acetamide), was the first nootropic (from the Greek noos ‘mind’ and tropos, ‘growth, movement towards’) drug to be introduced into clinical practice. The drug has been shown to facilitate learning and to prevent the development of amnesia under various experimental conditions [1]. Piracetam enhanced recovery from aphasia after stroke [5] and improved cognitive function in the elderly [6] and after coronary artery bypass [7]. The drug reversed hippocampal membrane alterations in Alzheimer’s disease [8] and inhibited the lipid-destabilizing effect of the amyloid peptide Abeta C-terminal fragment [9].

Vinpocetine (vinpocetine-ethyl apovincaminate), is a synthetic derivative of the alkaloid vincamine, an extract of the lesser periwinkle (Vinca minor), a wildflower. Vinpocetine is widely used to improve cognitive function in patients with cerebrovascular disease in consideration of its ability to increase cerebral blood flow, which in turn increases regional cerebral glucose uptake [2,10]. In patients with ischemic stroke and mild cognitive impairment, vinpocetine favorably influenced the cognitive status in patients with chronic hypoperfusion [11]. The drug prevented scopolamine- and hypoxia-induced impairment of passive avoidance retention in rats [12] and improved short-term memory processes in patients with flunitrazepam-induced impairment of memory [13].

Standardized extracts of the leaves of Ginkgo biloba (EGb 761) are widely used as cognitive and memory enhancers in the cerebral insufficiency that occurs during normal aging or that arises out of vascular or degenerative dementias, but with variable outcome [14,15]. Extracts of Ginkgo biloba contain 24% ginkgo-flavone glycosides and 6% terpenoids (ginkgolides, bilobalide). The herb has been shown to possess antioxidant and free radical scavenging activities [16], anti-inflammatory [17], vasodilatory [18] and rheological [19] properties. Extracts of Ginkgo biloba may possess amyloid precursor protein lowering capacity as well [20].

Cognitive impairment in schizophrenia is frequent. Spatial working memory or short-term place memory is impaired in schizophrenia and the effect of antipsychotics on cognition in patients with schizophrenia is an important issue that generates considerable debate. Studies have suggested worsening of memory tasks associated with the use of the typical antipsychotic haloperidol in healthy volunteers [21–23] and in schizophrenic patients [24] compared with patients treated with atypical neuroleptics such as risperidone, olanzapine, and ziprasidone, which improved cognition in several studies [25]. Researchers found remarkably reduced psychomotor performance in the haloperidol-treated group of schizophrenic patients compared with patients treated with atypical neuroleptics [24]. Procedural learning was also found to be poorer in haloperidol-treated patients than in normal control subjects, while no difference could be observed between olanzapine-treated patients and normal control subjects [23]. The view that atypical antipsychotics improve memory in patients with schizophrenia is, however, not supported by all studies. Short-term administration of olanzapine, and not of haloperidol, impeded several aspects of psychomotor function and verbal memory in healthy volunteers [26]. Not all domains of cognition seem to be equally affected by different antipsychotics and risperidone, olanzapine, and haloperidol did not improve social cognition in schizophrenia [27]. Cognitive improvement associated with the administration of antipsychotic medication may be a manifestation of improvement in general cortical information processing [28]. Other studies, however, have suggested that improvements of cognition in schizophrenia treated with second-generation antipsychotic medications might reflect simple practice effects (i.e. exposure, familiarity, and/or procedural learning), while medication effects on cognition remain modest [29]. In any event, there is clearly a need to treat patients with schizophrenia with cognition-enhancing medications.

In experimental animals, haloperidol, which blocks D2 dopamine receptors in the striatum, causes impairment of memory retention in terms of latency time to find the original location of the platform in a water-maze task [30]. Haloperidol as well as clozapine impaired the acquisition process and consolidation processes respectively in step-through test. Both drugs impaired spatial learning function in mice in the water maze task [31]. The present study was therefore designed to investigate the effect of the memory enhancing drugs piracetam, vinpocetine and Ginkgo biloba extract in terms of their ability to improve spatial memory in mice treated with haloperidol.

Materials and methods

Animals

Swiss male albino mice of 20–22 g body weight were employed. Standard laboratory food and water were provided ad libitum. Animal procedures were performed in accordance with the Ethics Committee of the National Research Centre and followed the recommendations of the National Institutes of Health Guide for Care and Use of Laboratory Animals (Publication No. 85–23, revised 1985). Equal groups of six mice each were used in all experiments.

Cognitive testing

The Morris water maze (MWM) was employed to test spatial learning and memory. The MWM is a paradigm that requires the mice to use spatial memory to find a hidden platform just below the surface of a pool of water, and to remember its location from a previous trial [32]. The mice must therefore use distal cues to effectively locate the platform. Accurate navigation is rewarded by escape from the pool. The maze consisted of a glass tank narrowed to 20 cm wide, 40 cm in height, 70 cm in length, filled to a depth of 21 cm with water maintained at 25 °C. The glass escape platform was hidden from sight, submerged 1 cm below the surface of the water at the end of the tank [33]. The effect of piracetam (50, 150 or 300 mg/ kg, i.p.), vinpocetine (1, 2 or 4 mg/ kg) or Ginkgo biloba extract (25, 50 or 150 mg/ kg) on working memory was studied in mice treated with haloperidol (2 mg/ kg, i.p.) to induce cognitive impairment [30]. Drugs were either co-administered with haloperidol or given 30 min before haloperidol administration in order to see whether a difference exists or not when cognitive enhancers are given prior to the drug- produced memory impairment. Mice rapidly learn to swim directly to the escape platform and climb out. Once a mouse reached the platform, it remained there for 15 sec (trial 1; reference memory or acquisition trial). At the end of each trial, the mouse was towel-dried, returned to its home cage (where a heat lamp was available), and 3 min elapsed before the next trial (trials 2 and 3; working memory or retrieval trial), using the same platform location and start position as trial 1. The latency to find the platform (in seconds) was assessed with a stopwatch.

Drugs

Haloperidol (Kahira Pharm and Chem. Co. Cairo, ARE), vinpocetine (Vinporal, Amrya. Pharm. Ind., Cairo, ARE), piracetam (Nootropil, Chemical Industries Development; CID, Cairo, ARE), Ginkgo biloba extract (EMA Pharm. Co., Cairo, ARE). All drugs were dissolved in isotonic (0.9% NaCl) saline solution immediately before use. The doses of drugs used in the study were based upon the human dose after conversion to that for mice, after conversion tables by Paget and Barnes [34]. The dose of haloperidol used in the study (2 mg/ kg) was chosen on the basis of similar studies by Terry et al [35,36]. The dose would be expected to achieve comparable (and therapeutically relevant) D2 receptor occupancy values in vivo (i.e., in the range 65–80%) and based on the fact that haloperidol is metabolized over three times faster in rats than in humans.

Statistical Analysis

Data are expressed as mean ± SEM. The data were analyzed by one way ANOVA and by repeated measures (session x treatment) ANOVA, followed by Duncan’s multiple range test, using SPSS software (SAS Institute Inc., Cary, NC). A probability value of less than 0.05 was considered statistically significant.

Results

Effect of nootropics on haloperidol-induced memory impairment

Spatial memory was tested in the Morris water maze test. Haloperidol substantially impaired water maze performance. The time taken to find the escape platform (latency) was significantly delayed by haloperidol (2 mg/ kg, i.p.). Animals given piracetam co-administered with haloperidol or given 30 min prior to the antipsychotic drug showed significantly shorter latencies, which indicated that learning had occurred immediately (Fig. 1). All groups exhibited learning and improved their performance with training, analyzed as the time taken to reach the hidden platform (F = 11.58; p <0.0001). There was also a significant effect of treatment (F = 136.96; p <0.0001) and a significant treatment χ session interaction (F = 2.87; p = 0.002).

**Fig. 1. Effect of piracetam on haloperidol-induced (2 mg/ kg, i.p.) impairment of learning and memory of mice in the Morris water maze test.**

Post-hoc comparison indicated significantly shorter latencies for location of the hidden platform on the part of all treated groups in trials 1, 3 and 3 compared with the haloperidol control group. Furthermore, in trial 2, the group treated with the highest dose of piracetam showed significantly shorter latencies than all other treatment groups.

Vinpocetine co-administered with haloperidol failed to improve cognitive performance on water maze test, but vinpocetine at 4 mg/ kg administered 30 min before haloperidol markedly reduced the latencies for location of the submerged platform (Fig. 2). There was a significant drug effect (F = 105.34; p <0.0001), but insignificant session effect (F = 1.99; p = 0.143) or treatment χ trial interaction (F = 0.434; p = 0.96).

**Fig. 2. Effect of vinpocetine on haloperidol-induced (2 mg/ kg, i.p.) impairment of learning and memory of mice in the Morris water maze test.**

In trial 1, post-hoc comparisons indicated significantly shorter escape latencies for mice co-treated or pretreated with 4 mg/ kg vinpocetine compared with other treatment groups. In trial 2, co-treatment with 2–4 mg/ kg vinpocetine as well as pretreatment with 1–4 mg/ kg vinpocetine was associated with significantly shorter escape latencies compared with haloperidol control. In trial 3, co-treatment with 4 mg/ kg vinpocetine as well as pretreatment with 1–4 mg/ kg vinpocetine was associated with significantly shorter escape latencies compared with haloperidol control. Meanwhile, co--treatment or pretreatment with 4 mg/ kg vinpocetine resulted in significantly shorter escape latencies compared with other treatment groups. Thus the highest dose of vinpocetine resulted in significantly shorter escape latencies in all trials compared with the haloperidol-control group.

Mice treated with Ginkgo biloba extract showed worsening of their performance on the water maze test with markedly increased time to find the hidden platform (Fig. 3). Repeated ANOVA measures indicated a significant treatment effect, F = 92.5; p <0.0001, but insignificant trial effect, F = 1.98; p = 0.144 or treatment χ trial interaction, F = 1.74; p = 0.64.

**Fig. 3. Effect of Ginkgo biloba extract on haloperidol-induced (2 mg/kg, i.p.) impairment of learning and memory of mice in the Morris water maze test.**

Post-hoc comparisons revealed a significant increase in escape latencies in trial 1, 2 and 3 on co-treatment with 150 mg/ kg ginkgo and by pretreatment with 50 or 150 mg/ kg of Ginkgo biloba extract compared with other treatment groups. In addition, pretreatment with 150 mg/ kg of Ginkgo biloba extract was associated with significant increase in escape latencies in trial 2 and 3 compared with other treatment groups.

Discussion

In the current study, haloperidol substantially impaired the water maze performance of mice. Both the acquisition and retention of information were impaired by the drug. The dopaminergic system plays an important role in memory processes [37,38]. Studies have suggested that D2-like receptors have a greater contribution to make than D1-like receptors to both spatial working memory and object-location associative memory [39]. The D2-dopaminergic system is involved in the induction of basolateral amygdala to long-term potentiation of the dentate gyrus [40]. Haloperidol impaired spatial working memory performance and planning ability in healthy volunteers [21,22] and worsened recent autobiographical memory scores of patients with Alzheimer’s disease [41]. In experimental animals haloperidol, and to lesser extent olanzepine and risperidone, impaired working memory performance [42]. In the current study, the dose of haloperidol used was shown to impaire locomotor activity in a previous task [43] and drug influence on motor activity cannot be ruled out, but the water maze test is primarily a test of cognition (spatial learning/memory) [44]. Other workers have reached the conclusion that the negative effects of haloperidol in the water maze task are likely to be memory-related [35].

The current study investigated the effect of the nootropic drugs piracetam, vinpocetine and Ginkgo biloba extract on haloperidol-induced impairment of learning and memory in the water maze test. Favorable effects were observed after piracetam and the highest dose of vinpocetine examined, but not after Ginkgo biloba extract. Piracetam administered either as co-treatment or pretreatment markedly alleviated the impairment of learning and memory induced by haloperidol. The drug appeared to be nearly equally effective at all doses examined (50, 100 and 300 mg/ kg). Piracetam has proved effective in several models of amnesia. It has been shown to facilitate learning and retrieval of information and protect the brain from physical and chemical intoxication [45]. It reverses the amnesia induced by scopolamine, electroconvulsive shock and morphine as well as that caused by hypoxia [46,47]. Piracetam has negated the amnesiastic effect of 6-hydroxydopamine and restored to control values the noradrenaline level in the frontal cortex and hippocampus [48]. It has been shown to increase cortical and striatal monoamines [49,50], which might underlie its cognitive enhancing properties.

The latency of haloperidol-treated mice in location of the submerged platform in the MWM test was also reduced by 4 mg/ kg vinpocetine given either at the same time as haloperidol administration or 30 min prior to haloperidol. Other researchers have shown that vinpocetine prevented scopolamine- and hypoxia-induced impairment of passive avoidance retention in rats [12]. Vinpocetine and its main metabolite cis-apovincaminic acid protects against NMDA-induced neurotoxicity in a rat model of dementia. Behavioral deficits, such as impaired recognition of novel objects and spatial learning performance in the Morris maze, lesion size and microglia activation, have been markedly alleviated by vinpocetine and cis-apovincaminic acid [51]. The drug improved flunitrazepam-induced impairment of memory in healthy volunteers treated with flunitrazepam [13], and led to significant cognitive improvement in elderly patients with chronic cerebral dysfunction [52] as well as in patients with ischemic stroke and mild cognitive impairment [11]. Other researchers found no clear benefit demonstrated in patients with acute ischemic stroke [53]. The drug reduced accumulation of reactive oxygen species and blocked the inhibition of the mitochondrial respiratory chain complexes II–III and IV induced in cells by toxic concentrations of Aβ peptides [54]. In vitro, vinpocetine in a 1–50 µM/ ml concentration range protected against glutamate excitotoxicity in primary cortical neuronal cultures [55]. The drug binds to the peripheral-type benzodiazepine receptor involved in the mitochondrial transition pore complex [56] and reduces the decrease in mitochondrial inner membrane potential induced by glutamate exposure [55]. These properties are likely to mediate the beneficial influence of vinpocetine in cerebrovascular disease. In patients with Alzheimer’s disease, vinpocetine up to 60 mg per day, however, failed to improve cognition or overall functioning [57].

Ginkgo biloba extract extracts are widely used to treat memory disorders, although their value is not yet clear. In one study in patients with mild cognitive impairment, about half of the patients treated with Ginkgo biloba extract experienced an improvement in memory and their ability to concentrate, as well as a decrease in symptoms of forgetfulness [58]. In a randomized clinical trial, Ginkgo biloba extract neither altered the risk of progression from normal to clinical dementia nor protected against decline in memory function [59]. In another study, Ginkgo biloba extract at 120 mg twice a day was not effective in reducing either the overall incidence rate of dementia or Alzheimer’s disease incidence in elderly individuals with normal cognition or those with mild cognitive impairment [60]. Ginkgo biloba extract (120 mg per day) had no significant effect on a wide range of cognitive abilities, executive function, attention and mood in healthy older adults and in young adults [61]. In healthy young volunteers, Ginkgo biloba extract administration improved quality of memory 1 and 4 h post-dosing, but decreased the speed of attention task performance [62]. In rats subjected to chronic restraint stress, Ginkgo biloba extract decreased hippocampal neuronal loss and cognitive dysfunction [63] and improved spatial memory [64]. It was also effective in reducing, at least partially, both cognitive impairments and hippocampal damage after transient forebrain ischemia in rats [65]. Others have suggested that Ginkgo biloba extract does not enhance short-term working memory or long-term memory reference, but rather promotes learning of spatial information [66] and that Ginkgo biloba extract does not offer any continued beneficial effects in an already-learned working memory task [67]. The effects of Ginkgo biloba extract on spatial memory have been ascribed to cholinergic activity and perhaps partly to a histaminergic mechanism [68], to increased synaptic plasticity [69] and to increased level of 5-hydroxytryptamine in the hippocampus [70]. In this study, the administration of Ginkgo biloba extract even made impairment of cognitive performance induced by haloperidol worse in the water maze test, leading to higher latencies of location for the platform.

In summary, the current study showed that piracetam and vinpocetine, but not the herbal remedy Ginkgo biloba extract, alleviated the impairment of learning and memory induced by the typical antipsychotic haloperidol. Further studies are warranted in patients with schizophrenia to ascertain whether Ginkgo biloba extract might be suitable for improving cognitive function in patients on antipsychotic drug therapy and to evaluate the utility of using piracetam and vinpocetine to improve cognition in patients treated with classic antipsychotic drugs.

Omar M.E. Abdel-Salam
Department of Pharmacology, Toxicology and Narcotics
National Research Centre
Tahrir Street
Dokki
Cairo, Egypt
e-mail: omasalam@hotmail.com

Zdroje

1. Shorvon S. Pyrrolidone derivatives. Lancet 2001; 358(9296): 1885–1892.

2. Vas A, Gulyás B, Szabó Z, Bönöczk P, Csiba L, Kiss B et al. Clinical and non-clinical investigations using positron emission tomography, near infrared spectroscopy and transcranial Doppler methods on the neuroprotective drug vinpocetine: a summary of evidences. J Neurol Sci 2002; 15: 203–204, 259–262.

3. DeFeudis FV, Drieu K. Ginkgo biloba extract (EGb 761) and CNS functions: basic studies and clinical applications. Curr Drug Targets 2000; 1(1): 25–58.

4. Giurgea C. The “nootropic” approach to the pharmacology of the integrative activity of the brain. Cond Reflex 1973; 8(2): 108–115.

5. Kessler J, Thiel A, Karbe H, Heiss WD. Piracetam improves activated blood flow and facilitates rehabilitation of poststroke aphasic patients. Stroke 2000; 31(9): 2112–2116.

6. Waegemans T, Wilsher CR, Danniau A, Ferris SH, Kurz A, Winblad B. Clinical efficacy of piracetam in cognitive impairment: a meta-analysis. Dement Geriatr Cogn Disord 2002; 13(4): 217–224.

7. Holinski S, Claus B, Alaaraj N, Dohmen PM, Kirilova K, Neumann K et al. Cerebroprotective effect of piracetam in patients undergoing coronary bypass surgery. Med Sci Monit 2008; 14(11): PI53–PI57.

8. Eckert GP, Cairns NJ, Muller WE. Piracetam reverses hippocampal membrane alterations in Alzheimer’s disease. J Neural Transm 1999; 106(7–8): 757–761.

9. Mingeot-Leclercq MP, Lins L, Bensliman M, Thomas A, Van Bambeke F, Peuvot J et al. Piracetam inhibits the lipid-destabilising effect of the amyloid peptide Abeta C-terminal fragment. Biochim Biophys Acta 2003; 1609(1): 28–38.

10. Szilágyi G, Nagy Z, Balkay L, Boros I, Emri M, Lehel S et al. Effects of vinpocetine on the redistribution of cerebral blood flow and glucose metabolism in chronic ischemic stroke patients: a PET study. J Neurot Sci 2005; 15: 229–230, 275–284.

11. Valikovics A. Investigation of the effect of vinpocetine on cerebral blood flow and cognitive functions. Ideggyogy Sz 2007; 60(7–8): 301–310.

12. DeNoble VJ, Repetti SJ, Gelpke LW, Wood LM, Keim KL. Vinpocetine: nootropic effects on scopolamine-induced and hypoxia-induced retrieval deficits of a step-through passive avoidance response in rats. Pharmacol Biochem Behav 1986; 24(4): 1123–1128.

13. Bhatti JZ, Hindmarch I. Vinpocetine effects on cognitive impairments produced by flunitrazepam. Int Clin Psychopharmacol 1987; 2(4): 325–231.

14. Oken BS, Storzbach DM, Kaye JA. The efficacy of Ginkgo biloba on cognitive function in Alzheimer disease. Arch Neurol 1998; 55(11): 1409–1415.

15. Dodge HH, Zitzelberger T, Oken BS, Howieson D, Kaye J. A randomized placebo-controlled trial of Ginkgo biloba for the prevention of cognitive decline. Neurology 2008; 70(19): 1809–1817.

16. Schindowski K, Leutner S, Kressmann S, Eckert A, Müller WE. Age-related increase of oxidative stress-induced apoptosis in mice prevention by Ginkgo biloba extract (EGb761). J Neural Transm 2001; 108(8–9): 969–978.

17. Abdel-Salam OM, Baiuomy AR, El-Batran S, Arbid MS. Evaluation of the anti-inflammatory, anti-nociceptive and gastric effects of Ginkgo biloba in the rat. Pharmacol Res 2004; 49(2): 133–142.

18. Chung HS, Harris A, Kristinsson JK, Ciulla TA, Kagemann C, Ritch R. Ginkgo biloba extract increases ocular blood flow velocity. J Ocul Pharmacol Ther 1999; 15(3): 233–240.

19. Költringer P, Langsteger W, Klima G, Reisecker F, Eber O. Hemorheologic effects of Ginkgo biloba extract EGb 761. Dose-dependent effect of EGb 761 on microcirculation and viscoelasticity of blood. Fortschr Med 1993; 111(1): 170–172.

20. Augustin S, Rimbach G, Augustin K, Schliebs R, Wolffram S, Cermak R. Effect of a short- and long-term treatment with Ginkgo biloba extract on amyloid precursor protein levels in a transgenic mouse model relevant to Alzheimer’s disease. Arch Biochem Biophys 2009; 481(2): 177–182.

21. Legangneux E, McEwen J, Wesnes K, Berougnan L, Miget N, Canal M et al. The acute effects of amisulpride (50 mg and 200 mg) and haloperidol (2 mg) on cognitive function in healthy elderly volunteers. J Psychopharmacol 2000; 14(2): 164–171.

22. Lustig C, Meck WH. Chronic treatment with haloperidol induces deficits in working memory and feedback effects of interval timing. Brain Cogn 2005; 58(1): 9–16.

23. Paquet F, Soucy JP, Stip E, Lévesque M, Elie A, Bédard MA. Comparison between olanzapine and haloperidol on procedural learning and the relationship with striatal D2 receptor occupancy in schizophrenia. J Neuropsychiatry Clin Neurosci 2004; 16(1): 47–56.

24. Kagerer S, Winter C, Möller HJ, Soyka M. Effects of haloperidol and atypical neuroleptics on psychomotor performance and driving ability in schizophrenic patients results from an experimental study. Neuropsychobiology 2003; 47(4): 212–218.

25. Meltzer HY, Park S, Kessler R. Cognition, schizophrenia, and the atypical antipsychotic drugs. Proc Natl Acad Sci U S A 1999; 96(24): 13591–13593.

26. Morrens M, Wezenberg E, Verkes RJ, Hulstijn W, Ruigt GS, Sabbe BG. Psychomotor and memory effects of haloperidol, olanzapine, and paroxetine in healthy subjects after short-term administration. J Clin Psychopharmacol 2007; 27(1): 15–21.

27. Sergi MJ, Green MF, Widmark C, Reist C, Erhart S, Braff DL et al. Social cognition and neurocognition: effects of risperidone, olanzapine, and haloperidol. Am J Psychiatry 2007; 164(10): 1585–1592.

28. Weickert TW, Goldberg TE. First- and second-generation antipsychotic medication and cognitive processing in schizophrenia. Curr Psychiatry Rep 2005; 7(4): 304–310.

29. Goldberg TE, Goldman RS, Burdick KE, Malhotra AK, Lencz T, Patel RC et al. Cognitive improvement after treatment with second-generation antipsychotic medications in first-episode schizophrenia: is it a practice effect? Arch Gen Psychiatry 2007; 64(10): 1115–1122.

30. Colpo G, Trevisol F, Teixeira AM, Fachinetto R, Pereira RP, Athayde ML et al. Ilex paraguariensis has antioxidant potential and attenuates haloperidol-induced orofacial dyskinesia and memory dysfunction in rats. Neurotox Res 2007; 12(3): 171–180.

31. Hou Y, Wu CF, Yang JY, Guo T. Differential effects of haloperidol, clozapine and olanzapine on learning and memory functions in mice. Prog Neuropsychopharmacol Biol Psychiatry 2006; 30(8): 1486–1495.

32. Morris R. Developments of a water-maze procedure for studying spatial learning in the rat. J Neurosci Methods 1984; 11(1): 47–60.

33. Dunnett SB, Bensadoun JC, Pask T, Brooks S. Assessment of motor impairments in transgenic mice. In: Crawley JN (ed). Mouse behavioral phenotyping. Washington DC: Society for Neuroscience; 2003: 1–13.

34. Paget GE, Barnes JM. Toxicity tests. In: Laurence DR, Bacharach AL (eds). Evaluation of Drug Activities Pharmacometrics. London: Academic Press 1964: 1–135.

35. Terry AV jr, Hill WD, Parikh V, Waller JL, Evans DR, Mahadik SP. Differential effects of haloperidol, risperidone, and clozapine exposure on cholinergic markers and spatial learning performance in rats. Neuropsychopharmacology 2003; 28(2): 300–309.

36. Terry AV jr, Parikh V, Gearhart DA, Pillai A, Hohnadel E, Warner S et al. Time-dependent effects of haloperidol and ziprasidone on nerve growth factor, cholinergic neurons, and spatial learning in rats. J Pharmacol Exp Ther 2006; 318(2): 709–724.

37. Landau SM, Lal R, O‘Neil JP, Baker S, Jagust WJ. Striatal dopamine and working memory. Cerebral Cortex 2009; 19(2): 445–454.

38. Cools R, Gibbs SE, Miyakawa A, Jagust W, D’Esposito M. Working memory capacity predicts dopamine synthesis capacity in the human striatum. J Neurosci 2008; 28(5): 1208–1212.

39. Von Huben SN, Davis SA, Lay CC, Katner SN, Crean RD, Taffe MA. Differential contributions of dopaminergic D1- and D2-like receptors to cognitive function in rhesus monkeys. Psychopharmacology (Berl) 2006; 188(4): 586–596.

40. Abe K, Niikura Y, Fujimoto T, Akaishi T, Misawa M. Involvement of dopamine D2 receptors in the induction of long-term potentiation in the basolateral amygdala-dentate gyrus pathway of anesthetized rats. Neuropharmacology 2008; 55(8): 1419–1424.

41. Harrison BE, Therrien B. Effect of antipsychotic medication use on memory in patients with Alzheimer’s disease: assessing the potential risk for accelerated recent autobiographical memory loss. J Gerontol Nurs 2007; 33(6): 11–20.

42. Karl T, Duffy L, O’Brien E, Matsumoto I, Dedova I. Behavioural effects of chronic haloperidol and risperidone treatment in rats. Behav Brain Res 2006; 171(2): 286–294.

43. Abdel-Salam OM, Baiuomy AR. Effect of different drugs influencing monoamine neurotransmission on haloperidol-induced catalepsy in mice. Turk J Med Sci 2007; 37(6): 333–338.

44. Hamm RJ, Dixon CD, Gbadebo DM, Singha AK. Jenkins LW, Lyeth BC et al. Cognitive deficits following traumatic brain injury produced by controlled conical impact. J Neurotrauma 1992; 9(1): 11–20.

45. Nicholson CD. Pharmacology of nootropics and metabolically active compounds in relation to their use in dementia. Psychopharmacology (Berl) 1990; 101(2): 147–159.

46. Gouliaev AH, Senning A. Piracetam and other structurally related nootropics. Brain Res Brain Res Rev 1994; 19(2): 180–222.

47. Aksu F, Gültekin I, Inan SY, Baysal F. The effects of piracetam on morphine-induced amnesia and analgesia: The possible contribution of central opiatergic mechanisms on the antiamnestic effect of piracetam. Inflammopharmacology 1998; 6(1): 53–65.

48. Stancheva S, Papazova M, Alova L, Lazarova-Bakarova M. Impairment of learning and memory in shuttle box-trained rats neonatally injected with 6-hydroxydopamine. Effects of nootropic drugs. Acta Physiol Pharmacol Bulg 1993; 19(3): 77–82.

49. Stancheva SL, Alova LG. Biogenic monoamine uptake by rat brain synaptosomes during aging. Effects of nootropic drugs. Gen Pharmacol 1994; 25)5): 981–987.

50. Budygin EA, Gaĭnetdinov RR, Titov DA, Kovalev GI. The effect of a low dose of piracetam on the activity of the dopaminergic system in the rat striatum. Eksp Klin Farmakol 1996; 59(2): 6–8.

51. Nyakas C, Felszeghy K, Szabó R, Keijser JN, Luiten PG, Szombathelyi Z et al. Neuroprotective effects of vinpocetine and its major metabolite cis-apovincaminic acid on NMDA-induced neurotoxicity in a rat entorhinal cortex lesion model. CNS Neurosci Ther 2009; 15(2): 89–99.

52. Balestreri R, Fontana L, Astengo F. A double-blind placebo controlled evaluation of the safety and efficacy of vinpocetine in the treatment of patients with chronic vascular senile cerebral dysfunction. J Am Geriatr Soc 1987; 35(5): 425–430.

53. Bereczki D, Fekete I. Vinpocetine for acute ischemic stroke. Stroke 2008; 39: 2404.

54. Pereira C, Agostinho P, Oliveira CA. Vinpocetine attenuates the metabolic dysfunction induced by amyloid-peptides in PC12 cells. Free Radical Research 2000; 33(5): 497–506.

55. Tárnok K, Kiss E, Luiten PG, Nyakas C, Tihanyi K, Schlett K et al. Effects of Vinpocetine on mitochondrial function and neuroprotection in primary cortical neurons. Neurochem Int 2008; 53(6–8): 289–295.

56. Gulyás B, Halldin C, Vas A, Banati RB, Shchukin E, Finnema S et al. [11C]vinpocetine: a prospective peripheral benzodiazepine receptor ligand for primate PET studies. J Neurol Sci 2005; 15: 229–230; 219–223.

57. Thal LJ, Salmon DP, Lasker B, Bower D, Klauber MR. The safety and lack of efficacy of vinpocetine in Alzheimer’s disease. J Am Geriatr Soc 1989; 37(6): 515–520.

58. Bäurle P, Suter A, Wormstall H. Safety and effectiveness of a traditional ginkgo fresh plant extract – results from a clinical trial. Forsch Komplementmed 2009; 16(3): 156–161.

59. Dodge HH, Zitzelberger T, Oken BS, Howieson D, Kaye J. A randomized placebo-controlled trial of Ginkgo biloba for the prevention of cognitive decline. Neurology 2008; 70(19): 1809–1817.

60. DeKosky ST, Williamson JD, Fitzpatrick AL, Kronmal RA, Ives DG, Saxton JA et al. Ginkgo biloba for prevention of dementia: a randomized controlled trial. JAMA 2008; 300(19): 2253–2262.

61. Burns NR, Bryan J, Nettelbeck T. Ginkgo biloba: no robust effect on cognitive abilities or mood in healthy young or older adults. Hum Psychopharmacol 2006; 21(1): 27–37.

62. Kennedy DO, Jackson PA, Haskell CF, Scholey AB. Modulation of cognitive performance following single doses of 120 mg Ginkgo biloba extract administered to healthy young volunteers. Hum Psychopharmacol 2007; 22(8): 559–566.

63. Takuma K, Hoshina Y, Arai S, Himeno Y, Matsuo A, Funatsu Y et al. Ginkgo biloba extract EGb 761 attenuates hippocampal neuronal loss and cognitive dysfunction resulting from chronic restraint stress in ovariectomized rats. Neuroscience 2007; 149(2): 256–262.

64. Walesiuk A, Braszko JJ. Preventive action of Ginkgo biloba in stress- and corticosterone-induced impairment of spatial memory in rats. Phytomedicine 2009; 16(1): 40–46.

65. Paganelli RA, Benetoli A, Milani H. Sustained neuroprotection and facilitation of behavioral recovery by the Ginkgo biloba extract, EGb 761, after transient forebrain ischemia in rats. Behav Brain Res 2006; 174(1): 70–77.

66. Shif O, Gillette K, Damkaoutis CM, Carrano C, Robbins SJ, Hoffman JR. Effects of Ginkgo biloba administered after spatial learning on water maze and radial arm maze performance in young adult rats. Pharmacol Biochem Behav 2006; 84(1): 17–25.

67. Satvat E, Mallet PE. Chronic administration of a Ginkgo biloba leaf extract facilitates acquisition but not performance of a working memory task. Psychopharmacology (Berl) 2009; 202(1–3): 173–185.

68. Yamamoto Y, Adachi Y, Fujii Y, Kamei C. Ginkgo biloba extract improves spatial memory in rats mainly but not exclusively via a histaminergic mechanism. Brain Res 2007; 1129(1): 161–165.

69. Wang Y, Wang L, Wu J, Cai J. The in vivo synaptic plasticity mechanism of EGb 761-induced enhancement of spatial learning and memory in aged rats. Br J Pharmacol 2006; 148(2): 147–153.

70. Blecharz-Klin K, Piechal A, Joniec I, Pyrzanowska J, Widy-Tyszkiewicz E. Pharmacological and biochemical effects of Ginkgo biloba extract on learning, memory consolidation and motor activity in old rats. Acta Neurobiol Exp (Wars) 2009; 69(2): 217–231.