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P.1.d.011 Phosphonate analogue of ketoglutarate increases activity of ketoglutarate dehydrogenasecomplex in situ and in vivo
S254
P.1.d Basic and clinical neuroscience – Animal models
D2 receptor occupancy was attained at a therapeutic dosage of asenapine (5 mg BID). In the rat brain, asenapine demonstrated dose-dependent (0.003−0.3 mg/kg) and exposure-related (plasma levels, 0.2−18.0 ng/mL) responses. The median effective dose (ED50 ) for D2 receptor occupancy in the rat striatum following subcutaneous (SC) administration of asenapine was 0.02 mg/kg, with 60% to 80% D2 receptor occupancy levels observed over a dose range of 0.03−0.1 mg/kg. Based on these data, asenapine doses in the range of 0.03−0.1 mg/kg (SC) in the rat are considered to approximate clinically effective doses of asenapine in humans. In support of this assertion, asenapine (SC) in this dose range was found to be effective in rat models predictive of antipsychotic-like activity (conditioned avoidance, apomorphine-disrupted prepulse inhibition, and amphetamine-stimulated locomotor activity, for which minimally effective SC doses of asenapine were 0.1 mg/kg, 0.03 mg/kg, and 0.03 mg/kg, respectively). Over this same dose range, asenapine was found to increase dopamine and acetylcholine efflux in the prefrontal cortex, reverse cognitive deficits induced by phencyclidine or lesions of the medial prefrontal cortex, and reverse the effects of chronic mild stress on sucrose intake in rats. In contrast, higher doses of asenapine (0.5 mg/kg SC) are required to induce catalepsy in rats, an index of the propensity of a drug to induce EPS. Conclusions: These data from animal models in the rat predict that asenapine has potent antipsychotic-like activity at doses associated with low EPS liability, a prediction that is consistent with the clinical profile of asenapine in patients with schizophrenia.
both in non-separated (37.7±7.2%, p < 0.05 and 34.7±5.8%, p < 0.05) and following maternal separation (64.1±6.2%, p < 0.05 and 58.5±7.2%, p < 0.05). In the FRL, maternal separation, escitalopram or nortriptyline had no significant effects. NPY-LI was reduced in the hippocampus (23.7±1.9 and 30.6±1.9 pmol/g, respectively; p < 0.05)but elevated in the periaqueductal grey (PAG) (107.6±21.4 and 60.0±8.7 pmol/g, respectively; p = 0.0052) and hypothalamus (335.8±10.9 and 212.5±15.9 pmol/g, respectively; p < 0.001) of the vulnerable FSL compared to the control FRL. However, NPY-LI levels were not affected by maternal separation or chronic antidepressant treatment. The FSL rats showed also decreased basal expression of hippocampal NPY mRNA in the CA1 (29.0±2.5 and 40.2±2.0 nCi/g, respectively; p < 0.001) and CA3 regions (25.4±1.8 and 31.3±1.7 nCi/g, respectively; p < 0.05), while Y1 receptor mRNA levels were increased in the CA1 region (13.3±0.7 and 11.2±0.3 nCi/g, respectively; p < 0.05) as compared to the control FRL rat. In conclusion, our findings suggest that environmental stress in early life may cause longterm alterations in behavioral regulation of an individual and demonstrate the efficacy of chronic antidepressant treatment with escitalopram and nortriptyline in reversing malfunctioned behavior caused by genetic and environmental stressors. Furthermore, our data provide additional support for the hypothesis that NPY system downregulation may play a role in the pathophysiology of depression and that one of the mechanisms involved could be altered Y1 receptor mediated NPY transmission. References
P.1.d.010 Effects of maternal separation and antidepressant treatment on adult brain and behavior in a rat model of depression A. El Khoury1 ° , M. Werme1 , S.H.M. Gruber1 , A.A. Math´e1 . 1 Karolinska Institutet, Clinical Neuroscience, Huddinge – Stockholm, Sweden Accumulating evidence shows that adverse experience in childhood is involved in adult life psychopathology [1]. Neuropeptide Y (NPY) has been previously demonstrated to be altered in selected brain regions of animal models of depression [2]. This study was conducted to investigate the effects of maternal separation and chronic treatment with the antidepressants SSRI escitalopram and the tricyclic nortriptyline on immobility in the Porsolt Swim Test and levels of NPY-like immunoreactivity (-LI) in specific brain regions of the Flinders Sensitive Line (FSL) rats and their controls Flinders Resistant Line (FRL) rats. In situ hybridization histochemistry was used to measure mRNA expression levels of NPY and NPY Y1 receptors. Male rat pups were separated from dam (MS) daily for 180 min from postnatal day 2 (PND2) to 14 (PND14) or left undisturbed (Non-MS). On PND43, the rats were assigned to dietary treatments with escitalopram, nortriptyline or vehicle admixed to food pellets until the end of the experiment on PND73. Immobility in the Porsolt swim test was measured on PND65, as an index for depressive-like behavior. The peptide data were subjected to two-way analysis of variance (ANOVA) to compare treatment responses. For data from in situ hybridization, an overall 3-way MANOVA was performed with strain, treatment and hippocampus region as different factors. In the genetically vulnerable FSL, immobility at baseline was significantly higher compared to the resistant FRL animals (67.01±9.7 and 41.4±6.6%, respectively; p < 0.05). Maternal separation further increased immobility in FSL (80.1±6.1%, p < 0.001). Treatment with escitalopram and nortriptyline reduced immobility in the FSL strain,
[1] Kendler, K.S., Neale, M.C., Kessler, R.C., Heath, A.C., Eaves, L.J., 1992. Childhood parental loss and adult psychopathology in women. A twin study perspective. Arch Gen Psychiatry 49, 109–116. [2] Math´e, A.A., Jim´enez, P.A., Theodorsson, E., Stenfors, C., 1998. Neuropeptide Y, neurokinin A and neurotensin in brain regions of Fawn Hooded “depressed”, Wistar, and Sprague Dawley rats. Effects of electroconvulsive stimuli. Prog Neuropsychopharmacol Biol Psychiatry 22, 529–546.
P.1.d.011 Phosphonate analogue of ketoglutarate increases activity of ketoglutarate dehydrogenasecomplex in situ and in vivo L.K. Trofimova1 , A.V. Graf1 ° , E.I. Klimuk2 , M.S. Kabysheva1 , N.A. Sokolova1 , V.I. Bunik2 . 1 Lomonosov Moscow State University, Biology Faculty Department of Human and Animal Phisiology, Moscow, Russia; 2 Lomonosov Moscow State University, Belozersky Institute of Physico-Chemical Biology, Moscow, Russia Alpha-ketoglutarate dehydrogenase complex (KGDC) is one of the key mitochondrial enzymes of the tricarboxylic acid cycle. Decrease in the complex activity is observed during different neurodegenerative diseases, such as Alzheimer, Parkinson and Huntington diseases, progressive supranuclear palsy [1]. Phosphonate analogues of 2-oxoglutarate are known as effective in situ inhibitors of KGDC, which can be used for modeling such diseases [2]. Disorders of nervous system are also observed in offspring after pathologies during pregnancy, such as hypoxia [3]. We examined the direct action of the phosphonate analogue on cell culture and its indirect effect on the offspring of the rats treated with the phosphonate during the critical period of pregnancy (period of early organogenesis) [3]. Methods: The phosphonate analogue of alpha-ketoglutarate was synthesized as in [2]. The primary culture of rat astrocytes
P.1.d Basic and clinical neuroscience – Animal models was treated with the phosphonate in the HBSS medium. The data (mean ? standard error) were obtained from the average values of the four activity assays in the control and experimental groups, repeated with the two independent cultures. Rats were treated on the 9−10th day of pregnancy by a single intranasal application of either physiological solution (control group, n = 4) or the phosphonate analogue (experimental group, n = 4). Total KGDC activity in the extracts of cultured astrocytes or cerebral cortex and cerebellum of 60-day old offspring was calculated as micromole of oxidized alpha-ketoglutarate per minute. Reaction rates were detected with an aliquote of the extracts, following an increase in the NADH fluorescence with excitation/emission at 360/465 nm or absorbance at 340 nm under conditions specified in [2]. Results: Astrocyte culture incubated with the phosphonate analogue showed a statistically significant increase in the total KGDHC activity of 35±8%. Application of the phosphonate analogue to pregnant rats led to an increase in the total KGDHC activity in the cortex and cerebellum of their male and female offspring, with the effect more pronounced in the cerebellum than in cortex (Table 1). Table 1. Total activity of KGDC (A, mean±standard error) in brain cortex and cerebellum of offspring, whose mothers got physiological solution (control group) or the phosphonate analogue (experimental group) during pregnancya Brain
Control group
Experimental group
structure
Males (n = 6)
Females (n = 7)
Males (n = 6)
A
A
A
Females (n = 6) % of control
A
% of control
Cortex 4.30±0.40 4.87±0.71 5.28±0.15** 123±3% 6.16±0.34* 127±8% Cerebellum 1.47±0.16 0.95±0.08 2.11±0.19** 144±11% 1.77±0.47** 187±8% a Significant
differences between the control and experimental group according to Student’s t-test are with p < 0.05 (**) or p < 0.08 (*).
Conclusions: Application of the phosphonate analogue of alpha-ketoglutarate to cultivated astrocytes or pregnant rats increases the total KGDC activity in the cellular extracts or in the brain cortex and cerebellum of the sexually mature offspring. In view of neuropathologies induced by a decrease in the KGDC activity, the opposite effect of the phosphonate analogue shown in our work may be used in developing new therapeutic strategies to cure such pathologies. References [1] Gibson, G.E., Blass, J.P., Beal, M.F., Bunik, V.I., 2005, The a-ketoglutarate dehydrogenase complex: A mediator between mitochondria and oxidative stress in neurodegeneration. Mol Neurobiol 31, 45−63. [2] Bunik, V.I., Denton, T.T., Xu, H., Thompson, C.M., Cooper, A.J., Gibson, G.E., 2005, Phosphonate analogues of alpha-ketoglutarate inhibit the activity of the alpha-ketoglutarate dehydrogenase complex isolated from brain and in cultured cells. Biochem 44(31), 10552−61. [3] Graf, A.V., 2005, Effects of hypoxia during early organogenesis of rats and the peptide correction of consequences. Ph.D. thesis, Moscow Lomonosov State University, Moscow.
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P.1.d.012 Comparison of donepezile, ispronicline, varenicline and vinpocetine in two types of learning paradigms in rodents J. Laszy1 ° , V. Rom´an1 , A. Szemzo2 , I. Gyerty´an1 . 1 Gedeon Richter Ltd., Behavioural Pharmacology, Budapest, Hungary; 2 Gedeon Richter Ltd., Chemistry IV., Budapest, Hungary The treatment of normal cognitive aging and pathological memory impairment associated with different type of dementia is a challenge for public health. In the preclinical phase of drug development cognitive models are crucial to select effective compounds. In the present study the memory improving effects of three types of cognitive enhancer drugs, the nicotinic a4b2 receptor agonists ispronicline and varenicline, the cholinesterase inhibitor donepezile and the nootropic vinpocetine were investigated in various learning paradigms in mice and rats. A place recognition test was carried out in NMRI mice using an asymmetric transparent plastic Y-maze with visual cues around the arms. In the acquisition trial, one of the symmetric arms of the maze was closed and the mouse was allowed to explore for 5 min. In the recognition trial followed by a selected intertrial delay, mice had free access to all three arms for 2 min. The time spent in the novel and the familiar arm was measured. One-way analysis of variance (ANOVA) was used for statistical comparison. The time-dependent forgetting induced by 6 h delay was not affected by either donepezile (0.5, 2 mg/kg ip.), ispronicline (0.5, 2 mg/kg sc.) or varenicline (1, 3 mg/kg sc.) given 30 min prior to both trials. A considerable deficit in the place recognition was induced by scopolamine (1 mg/kg ip. immediately after the acquisition trial) measured at 30 min intertrial delay. Donepezile significantly (p < 0.05) improved the recognition performance of mice, ispronicline showed a tendency to attenuate amnestic effect of scopolamine, while varenicline in a dose-range of 0.25−1 mg/kg sc. produced a complet reversal. Vinpocetine at ip. doses of 10 and 20 mg/kg did not exhibit protective effect. These compounds were also investigated in a water-labyrinth paradigm in Wistar rats. The animals had to swim through a labyrinth system making correct directional turns at three choice points. The number of errors was recorded in three daily sessions for three days. Statistical comparisons between parameters of each group were made by three-way ANOVA using ’groups’ as the independent betweeen groups factor, ’days’ and ’trials’ as the repeated measures factors and followed by post hoc Duncan-test. Donepezile (0.25−4 mg/kg p.o.) showed a significant, dosedependent protective effect against learning deficit induced by scopolamine (3 mg/kg ip.). Ispronicline at p.o. doses of 0.5 and 2 mg/kg produced 64% (p < 0.05) and 89% (p < 0.01) reversal, respectively, calculated for group means pooled over days. Varenicline at its lower dose (0.5 mg/kg p.o.) appeared to be effective, but 2 mg/kg practically did not counteract the effect of scopolamine. Vinpocetine at 10 mg/kg p.o. dose exerted 82% restoring effect (p < 0.001). The natural forgetting was not attenuated by the compounds tested in mice. However, the learning deficit produced by amnestic agent could be improved by the drugs with different mechanism of action in both models and species. These learning paradigms are appropriate to validate the cognitive enhancer profile of new drugs.
P.1.d Basic and clinical neuroscience – Animal models
D2 receptor occupancy was attained at a therapeutic dosage of asenapine (5 mg BID). In the rat brain, asenapine demonstrated dose-dependent (0.003−0.3 mg/kg) and exposure-related (plasma levels, 0.2−18.0 ng/mL) responses. The median effective dose (ED50 ) for D2 receptor occupancy in the rat striatum following subcutaneous (SC) administration of asenapine was 0.02 mg/kg, with 60% to 80% D2 receptor occupancy levels observed over a dose range of 0.03−0.1 mg/kg. Based on these data, asenapine doses in the range of 0.03−0.1 mg/kg (SC) in the rat are considered to approximate clinically effective doses of asenapine in humans. In support of this assertion, asenapine (SC) in this dose range was found to be effective in rat models predictive of antipsychotic-like activity (conditioned avoidance, apomorphine-disrupted prepulse inhibition, and amphetamine-stimulated locomotor activity, for which minimally effective SC doses of asenapine were 0.1 mg/kg, 0.03 mg/kg, and 0.03 mg/kg, respectively). Over this same dose range, asenapine was found to increase dopamine and acetylcholine efflux in the prefrontal cortex, reverse cognitive deficits induced by phencyclidine or lesions of the medial prefrontal cortex, and reverse the effects of chronic mild stress on sucrose intake in rats. In contrast, higher doses of asenapine (0.5 mg/kg SC) are required to induce catalepsy in rats, an index of the propensity of a drug to induce EPS. Conclusions: These data from animal models in the rat predict that asenapine has potent antipsychotic-like activity at doses associated with low EPS liability, a prediction that is consistent with the clinical profile of asenapine in patients with schizophrenia.
both in non-separated (37.7±7.2%, p < 0.05 and 34.7±5.8%, p < 0.05) and following maternal separation (64.1±6.2%, p < 0.05 and 58.5±7.2%, p < 0.05). In the FRL, maternal separation, escitalopram or nortriptyline had no significant effects. NPY-LI was reduced in the hippocampus (23.7±1.9 and 30.6±1.9 pmol/g, respectively; p < 0.05)but elevated in the periaqueductal grey (PAG) (107.6±21.4 and 60.0±8.7 pmol/g, respectively; p = 0.0052) and hypothalamus (335.8±10.9 and 212.5±15.9 pmol/g, respectively; p < 0.001) of the vulnerable FSL compared to the control FRL. However, NPY-LI levels were not affected by maternal separation or chronic antidepressant treatment. The FSL rats showed also decreased basal expression of hippocampal NPY mRNA in the CA1 (29.0±2.5 and 40.2±2.0 nCi/g, respectively; p < 0.001) and CA3 regions (25.4±1.8 and 31.3±1.7 nCi/g, respectively; p < 0.05), while Y1 receptor mRNA levels were increased in the CA1 region (13.3±0.7 and 11.2±0.3 nCi/g, respectively; p < 0.05) as compared to the control FRL rat. In conclusion, our findings suggest that environmental stress in early life may cause longterm alterations in behavioral regulation of an individual and demonstrate the efficacy of chronic antidepressant treatment with escitalopram and nortriptyline in reversing malfunctioned behavior caused by genetic and environmental stressors. Furthermore, our data provide additional support for the hypothesis that NPY system downregulation may play a role in the pathophysiology of depression and that one of the mechanisms involved could be altered Y1 receptor mediated NPY transmission. References
P.1.d.010 Effects of maternal separation and antidepressant treatment on adult brain and behavior in a rat model of depression A. El Khoury1 ° , M. Werme1 , S.H.M. Gruber1 , A.A. Math´e1 . 1 Karolinska Institutet, Clinical Neuroscience, Huddinge – Stockholm, Sweden Accumulating evidence shows that adverse experience in childhood is involved in adult life psychopathology [1]. Neuropeptide Y (NPY) has been previously demonstrated to be altered in selected brain regions of animal models of depression [2]. This study was conducted to investigate the effects of maternal separation and chronic treatment with the antidepressants SSRI escitalopram and the tricyclic nortriptyline on immobility in the Porsolt Swim Test and levels of NPY-like immunoreactivity (-LI) in specific brain regions of the Flinders Sensitive Line (FSL) rats and their controls Flinders Resistant Line (FRL) rats. In situ hybridization histochemistry was used to measure mRNA expression levels of NPY and NPY Y1 receptors. Male rat pups were separated from dam (MS) daily for 180 min from postnatal day 2 (PND2) to 14 (PND14) or left undisturbed (Non-MS). On PND43, the rats were assigned to dietary treatments with escitalopram, nortriptyline or vehicle admixed to food pellets until the end of the experiment on PND73. Immobility in the Porsolt swim test was measured on PND65, as an index for depressive-like behavior. The peptide data were subjected to two-way analysis of variance (ANOVA) to compare treatment responses. For data from in situ hybridization, an overall 3-way MANOVA was performed with strain, treatment and hippocampus region as different factors. In the genetically vulnerable FSL, immobility at baseline was significantly higher compared to the resistant FRL animals (67.01±9.7 and 41.4±6.6%, respectively; p < 0.05). Maternal separation further increased immobility in FSL (80.1±6.1%, p < 0.001). Treatment with escitalopram and nortriptyline reduced immobility in the FSL strain,
[1] Kendler, K.S., Neale, M.C., Kessler, R.C., Heath, A.C., Eaves, L.J., 1992. Childhood parental loss and adult psychopathology in women. A twin study perspective. Arch Gen Psychiatry 49, 109–116. [2] Math´e, A.A., Jim´enez, P.A., Theodorsson, E., Stenfors, C., 1998. Neuropeptide Y, neurokinin A and neurotensin in brain regions of Fawn Hooded “depressed”, Wistar, and Sprague Dawley rats. Effects of electroconvulsive stimuli. Prog Neuropsychopharmacol Biol Psychiatry 22, 529–546.
P.1.d.011 Phosphonate analogue of ketoglutarate increases activity of ketoglutarate dehydrogenasecomplex in situ and in vivo L.K. Trofimova1 , A.V. Graf1 ° , E.I. Klimuk2 , M.S. Kabysheva1 , N.A. Sokolova1 , V.I. Bunik2 . 1 Lomonosov Moscow State University, Biology Faculty Department of Human and Animal Phisiology, Moscow, Russia; 2 Lomonosov Moscow State University, Belozersky Institute of Physico-Chemical Biology, Moscow, Russia Alpha-ketoglutarate dehydrogenase complex (KGDC) is one of the key mitochondrial enzymes of the tricarboxylic acid cycle. Decrease in the complex activity is observed during different neurodegenerative diseases, such as Alzheimer, Parkinson and Huntington diseases, progressive supranuclear palsy [1]. Phosphonate analogues of 2-oxoglutarate are known as effective in situ inhibitors of KGDC, which can be used for modeling such diseases [2]. Disorders of nervous system are also observed in offspring after pathologies during pregnancy, such as hypoxia [3]. We examined the direct action of the phosphonate analogue on cell culture and its indirect effect on the offspring of the rats treated with the phosphonate during the critical period of pregnancy (period of early organogenesis) [3]. Methods: The phosphonate analogue of alpha-ketoglutarate was synthesized as in [2]. The primary culture of rat astrocytes
P.1.d Basic and clinical neuroscience – Animal models was treated with the phosphonate in the HBSS medium. The data (mean ? standard error) were obtained from the average values of the four activity assays in the control and experimental groups, repeated with the two independent cultures. Rats were treated on the 9−10th day of pregnancy by a single intranasal application of either physiological solution (control group, n = 4) or the phosphonate analogue (experimental group, n = 4). Total KGDC activity in the extracts of cultured astrocytes or cerebral cortex and cerebellum of 60-day old offspring was calculated as micromole of oxidized alpha-ketoglutarate per minute. Reaction rates were detected with an aliquote of the extracts, following an increase in the NADH fluorescence with excitation/emission at 360/465 nm or absorbance at 340 nm under conditions specified in [2]. Results: Astrocyte culture incubated with the phosphonate analogue showed a statistically significant increase in the total KGDHC activity of 35±8%. Application of the phosphonate analogue to pregnant rats led to an increase in the total KGDHC activity in the cortex and cerebellum of their male and female offspring, with the effect more pronounced in the cerebellum than in cortex (Table 1). Table 1. Total activity of KGDC (A, mean±standard error) in brain cortex and cerebellum of offspring, whose mothers got physiological solution (control group) or the phosphonate analogue (experimental group) during pregnancya Brain
Control group
Experimental group
structure
Males (n = 6)
Females (n = 7)
Males (n = 6)
A
A
A
Females (n = 6) % of control
A
% of control
Cortex 4.30±0.40 4.87±0.71 5.28±0.15** 123±3% 6.16±0.34* 127±8% Cerebellum 1.47±0.16 0.95±0.08 2.11±0.19** 144±11% 1.77±0.47** 187±8% a Significant
differences between the control and experimental group according to Student’s t-test are with p < 0.05 (**) or p < 0.08 (*).
Conclusions: Application of the phosphonate analogue of alpha-ketoglutarate to cultivated astrocytes or pregnant rats increases the total KGDC activity in the cellular extracts or in the brain cortex and cerebellum of the sexually mature offspring. In view of neuropathologies induced by a decrease in the KGDC activity, the opposite effect of the phosphonate analogue shown in our work may be used in developing new therapeutic strategies to cure such pathologies. References [1] Gibson, G.E., Blass, J.P., Beal, M.F., Bunik, V.I., 2005, The a-ketoglutarate dehydrogenase complex: A mediator between mitochondria and oxidative stress in neurodegeneration. Mol Neurobiol 31, 45−63. [2] Bunik, V.I., Denton, T.T., Xu, H., Thompson, C.M., Cooper, A.J., Gibson, G.E., 2005, Phosphonate analogues of alpha-ketoglutarate inhibit the activity of the alpha-ketoglutarate dehydrogenase complex isolated from brain and in cultured cells. Biochem 44(31), 10552−61. [3] Graf, A.V., 2005, Effects of hypoxia during early organogenesis of rats and the peptide correction of consequences. Ph.D. thesis, Moscow Lomonosov State University, Moscow.
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P.1.d.012 Comparison of donepezile, ispronicline, varenicline and vinpocetine in two types of learning paradigms in rodents J. Laszy1 ° , V. Rom´an1 , A. Szemzo2 , I. Gyerty´an1 . 1 Gedeon Richter Ltd., Behavioural Pharmacology, Budapest, Hungary; 2 Gedeon Richter Ltd., Chemistry IV., Budapest, Hungary The treatment of normal cognitive aging and pathological memory impairment associated with different type of dementia is a challenge for public health. In the preclinical phase of drug development cognitive models are crucial to select effective compounds. In the present study the memory improving effects of three types of cognitive enhancer drugs, the nicotinic a4b2 receptor agonists ispronicline and varenicline, the cholinesterase inhibitor donepezile and the nootropic vinpocetine were investigated in various learning paradigms in mice and rats. A place recognition test was carried out in NMRI mice using an asymmetric transparent plastic Y-maze with visual cues around the arms. In the acquisition trial, one of the symmetric arms of the maze was closed and the mouse was allowed to explore for 5 min. In the recognition trial followed by a selected intertrial delay, mice had free access to all three arms for 2 min. The time spent in the novel and the familiar arm was measured. One-way analysis of variance (ANOVA) was used for statistical comparison. The time-dependent forgetting induced by 6 h delay was not affected by either donepezile (0.5, 2 mg/kg ip.), ispronicline (0.5, 2 mg/kg sc.) or varenicline (1, 3 mg/kg sc.) given 30 min prior to both trials. A considerable deficit in the place recognition was induced by scopolamine (1 mg/kg ip. immediately after the acquisition trial) measured at 30 min intertrial delay. Donepezile significantly (p < 0.05) improved the recognition performance of mice, ispronicline showed a tendency to attenuate amnestic effect of scopolamine, while varenicline in a dose-range of 0.25−1 mg/kg sc. produced a complet reversal. Vinpocetine at ip. doses of 10 and 20 mg/kg did not exhibit protective effect. These compounds were also investigated in a water-labyrinth paradigm in Wistar rats. The animals had to swim through a labyrinth system making correct directional turns at three choice points. The number of errors was recorded in three daily sessions for three days. Statistical comparisons between parameters of each group were made by three-way ANOVA using ’groups’ as the independent betweeen groups factor, ’days’ and ’trials’ as the repeated measures factors and followed by post hoc Duncan-test. Donepezile (0.25−4 mg/kg p.o.) showed a significant, dosedependent protective effect against learning deficit induced by scopolamine (3 mg/kg ip.). Ispronicline at p.o. doses of 0.5 and 2 mg/kg produced 64% (p < 0.05) and 89% (p < 0.01) reversal, respectively, calculated for group means pooled over days. Varenicline at its lower dose (0.5 mg/kg p.o.) appeared to be effective, but 2 mg/kg practically did not counteract the effect of scopolamine. Vinpocetine at 10 mg/kg p.o. dose exerted 82% restoring effect (p < 0.001). The natural forgetting was not attenuated by the compounds tested in mice. However, the learning deficit produced by amnestic agent could be improved by the drugs with different mechanism of action in both models and species. These learning paradigms are appropriate to validate the cognitive enhancer profile of new drugs.