Behavioral effects of Ginkgo biloba L., Panax ginseng C.A. Mey. and Gincosan.

The behavioral effects of a standardized extract from Panax ginseng roots (G115), of a standardized extract from Ginkgo biloba leaves (GK501) and of their combination (PHL-00701) (Gincosan) were examined in experiments on rats with undisturbed memory and on rats with experimentally-impaired memory (by alcohol or by muscarinic- and dopamine-receptor antagonists), using methods for active avoidance (shuttle-box) and passive avoidance (step-down and step-through). On multiple administration G115, GK501 and PHL-00701 exerted favorable effects on learning and memory. These effects varied with the dose and administration schedules, with the rat strain and with the behavioral method. Based on earlier results, we discuss the role of changes in brain biogenic amines induced by the extracts in their mechanism of action. The present results allow for ranking G115, GK501 and their combination PHL-00701 (Gincosan) among cognition-enhancing (nootropic) drugs.

Memory effects of the Ca2+ and 5-HT antagonists dotarizine and flunarizine.

In experiments on Wistar and Long Evans rats, using behavioral methods for passive (step-down and step-through) and active (shuttle-box two-way avoidance with punishment reinforcement) the newly synthesized diphenyl-methyl-piperazine derivative with Ca2+ and 5-HT antagonistic action dotarizine (DOT) administered repeatedly at oral doses of 50 and 10 mg/kg in some cases improve memory process. Under the same experimental conditions the chemically related to dotarizine Ca2+ antagonist flunarizine significantly facilitated retention. In old (Long Evans and Wistar) rats DOT in large dose decreases values of learning criterion. Probably this is a manifestation of the inherent to drugs with nootropic action "therapeutic window". Earlier investigations of the same and other authors suggest the participation of serotonergic neurotransmission in the mechanism of the memory effects of the drug DOT.

Behavioral changes as a result of dotarizine or flunarizine influence on dopaminergic neurotransmission in the striatum.

In experiments on rats, we studied the changes in stereotypy induced by apomorphine (2.5 mg/kg i.p.) or amphetamine (2 mg/kg i.p.) and in haloperidol (1 mg/kg i.p.) catalepsy in rats treated with dotarizine (25 mg/kg orally), flunarizine (25 mg/kg) or vehicle for 10 days. Dotarizine did not induce any significant changes in the intensity and duration of apomorphine- or amphetamine-induced stereotypy nor in haloperidol-induced catalepsy. The flunarizine-induced changes in the behavioral effects of apomorphine, amphetamine and haloperidol suggest the decrease of striatal dopaminergic neurotransmission, whereby the risk of occurrence of extrapyramidal side effects of the drug when used in clinical practice. Dotarizine is not associated with such a risk.

Does nitric oxide participate in the mechanism of action of dotarizine?

Behavioral and nociceptive effects of dotarizine (DOT) and other substances acting on migrainous attacks and nitric oxide (NO) metabolism were studied in comparative experiments on rats. Behavioral effects were evaluated by the changes induced in ambulations and rearings of rats in the Opto-Varimex apparatus; effects on nociception were determined by the changes of pain threshold in growing mechanical pressure on one of the rat paw. The data showed that (1) NO did not participate directly in the mechanism of the behavioral actions of DOT. A role could be ascribed to the modulating influence of DOT on the changes in NO formation induced by other agents; (2) the NO system did not participate in the mechanisms of the responses to the painful mechanical pressure on the rat paw; (3) the behavioral effects of the substances with facilitating or inhibitory action on the migrainous process (m-CPP and ergotamine) and the influence of substances proved to affect NO formation (L-arginine, histamine, L-NAME) on these effects suggest a role for NO as a modulating but not a basic factor in the mechanisms of action of these pro- and antimigrainous substances; and (4) the behavioral effects of DOT were similar to the effects of the antimigrainous drug ergotamine and different from the promigrainous drug meta-chlorophenyl-piperazine (m-CPP)--which suggest an antimigrainous activity of dotarizine.

Behavorial responses to the 5-HT1A receptor antagonist NAN190 injected into rat CA1 hippocampal area.

1. Behavioral responses to unilateral and bilateral microinjections of the 5-HT1A receptor antagonist, NAN190 [1-(2-methoxyphenyl)-4-[4-(2-phthalimido) butyl]piperazine hydrobromide] (1 microgram), into the hippocampal CA1 area of male Wistar rats were studied. 2. NAN190 decreased locomotor activity (the number of horizontal and vertical movements). The effect was most pronounced with microinjections of NAN190 into the right hippocampus. 3. Microinjections of NAN190 facilitated learning and memory in shuttle-box testing. 4. Microinjections of NAN190 had an anxiogenic effect in elevated plus-maze experiments and Vogel's conflict test. 5. The different behavioral responses to left and right microinjections of NAN190 in some of the behavioral tests suggest functional asymmetry of 5-HT1A receptors in the CA1 hippocampal area.

Effect of dotarizine on K(+)-stimulated [3H]-serotonin and [3H]-acetylcholine release from rat hippocampus.

1. The effect of the diphenylmethyl-piperazine derivative dotarizine on K(+)-stimulated release of [3H]serotonin ([3H]5-HT) and [3H]acethylcholine ([3H]Ach) in rat hippocampal slices was studied. 2. Dotarizine at a concentration of 10(-6) M significantly decreased the basal [3H]5-HT release and, at a concentration of 10(-5) M, it significantly decreased the K(+)-stimulated [3H]5-HT release compared to vehicle controls. 3. Dotarizine, at a concentration of 5 x 10(-7) M, significantly increased both basal and K(+)-stimulated [3H]Ach release. At higher concentrations (10(-6) and 2 x 10(-6) M), dotarizine did not change the basal release but significantly increased the K(+)-stimulated [3H]Ach release. The effect of dotarizine on K(+)-stimulated [3H]Ach release decreased with increasing dotarizine concentrations. 4. It is speculated that, in addition to its Ca2+ antagonistic activity, dotarizine exerts an antagonistic effect on the presynaptic 5-HT autoreceptors, which could account for the facilitation of [3H]Ach release.

Anxiolytic effects of dotarizine, a possible antimigraine drug.

In experiments on rats in elevated plus-maze and in Opto Varimex apparatus, used for studying exploratory behavior, we observed that dotarizine (DOT), a drug with Ca2+ and 5-HT1/5-HT2-receptor antagonistic action, exerted effects suggesting anxiolytic action. The 5-HT uptake inhibitor fluoxetine (FLU) produced mainly anxiogenic effects. The simultaneous administration of DOT and FLU weakened the anxiolytic effect of DOT. The effects of the 5-HT1B/5-HT1C receptor agonist with promigraine action, m-chlorophenylpiperazine (m-CPP), indicated anxiogenic action, which was increased to a certain extent when it was combined with FLU. Some of the other 5-HT-receptor agonists and antagonists tested showed anxiogenic action and others anxiolytic action. In most cases, these effects were changed when they were administered simultaneously with FLU. DOT increased general locomotor activity and when combined with FLU this effect tended to decrease. In contrast, m-CPP decreased general locomotor activity and this effect was potentiated by FLU. DOT at the two doses used did not significantly change the rate of development of habituation, while m-CPP, buspirone and ondansetron increased it. The behavioral effects of DOT observed in all cases opposite to the same effects of the promigraine drug m-CPP suggest an antimigraine action of DOT.

Participation of different 5-HT receptors in the memory process in rats and its modulation by the serotonin depletor p-chlorophenylalanine.

The memory effects of agonists and antagonists of some serotonin (5-HT) receptor subtypes were examined in experiments on rats using an active avoidance method (shuttle-box). The 5-HT receptor antagonists NAN 190 (1 mg/kg i.p.) and pindolol (6 mg/kg i.p.) improved some indices for memory; the 5-HT2 and 5-HT3 receptor antagonists ritanserin (1 mg/kg i.p.) and ondansetron (0.1 mg/kg i.p.) exerted a favourable effect on the mastering of active avoidance performance. The tryptophan hydroxylase inhibitor para-chlorophenylalanine (300 mg/kg i.p.) alone produced no significant changes in the indices for retention of learned behaviour but in combination with the 5-HT-receptor agonists and antagonists influenced some of their effects. The results obtained show different participation of 5-HT1A, 5-HT2 and 5-HT3 receptors in the mechanisms of the memory process; the nature of this involvement is modulated by the brain level of serotonin.

Effect of dotarizine on electroconvulsive shock or pentylenetetrazol-induced amnesia and on seizure reactivity in rats.

Dotarizine (DOT), a compound performing both as calcium antagonist and as 5-HT2 receptor antagonist, was evaluated for its ability to protect against electroconvulsive shock (ECS)- and pentylenetetrazol (PTZ)-induced performance deficit in a passive avoidance "step-down" task in rats. Its effect on electric and PTZ seizure models was also studied. DOT administered orally at a dose of 50 mg/kg for 5 days before learning had no significant effect on retention tests given 3 h, 24 h and 7 days after the training session. It should be noted, however, that DOT completely prevented ECS- and PTZ-induced amnesia in passive avoidance situation. DOT had a pronounced protective effect against electric seizures but did not affect PTZ seizures. The present results provide additional evidence for the role of serotonergic neurotransmitter system and calcium homeostasis for memory and seizure reactivity and may be important in the development of effective treatment strategies for memory dysfunction.

Effects on nociception of the Ca2+ and 5-HT antagonist dotarizine and other 5-HT receptor agonists and antagonists.

The effects of the Ca2+ and 5-HT1 and 5-HT2 receptor antagonist dotarizine and of some other agonists and antagonists of different 5-HT receptor subtypes administered alone or in combination with the 5-HT uptake inhibitor fluoxetine (FLU) on nociception were studied, using a foot-pressure method (analgesy-meter testing). Dotarizine (DOT) administered at a dose of 50 mg/kg for 3 days orally significantly increased the pain threshold. Fluoxetine (FLU) administered at a dose of 10 mg/kg for 3 days also significantly increased the pain threshold. The combination of DOT and FLU abolished the analgesic effects of the two drugs. The 5-HT1A and 5-HT1B/1C receptor agonists buspirone and m-CPP decreased the pain threshold. The antagonists of 5-HT1A(NAN-190),5-HT1/5-HT2(methysergide), 5-HT2 (ritanserin), and 5-HT3 (ondansetron) receptors as well as the agonists of 5-HT2(DOI) and 5-HT3 (mCPBG) receptors increased the pain threshold. Fluoxetine at a single dose of 10 mg/kg differently influenced the effects of the 5-HT agonists and antagonists on nociception. Comparison of the effects of dotarizine with the effects of some of the agonists and antagonists of 5-HT receptor subtypes on the nociceptive and other actions suggests the possibility of a therapeutic value of dotarizine as an antimigraine drug.

The 5-HT2 receptor antagonist ketanserine prevents electroconvulsive shock- and clonidine-induced amnesia.

The 5-HT2-selective antagonist ketanserine was examined for its ability to prevent electroconvulsive shock (ECS)- or clonidine-induced performance deficit in the passive avoidance situation (step-down) in rats. The posttrain intraperitoneal injection of ketanserine at doses of 3 and 10 mg/kg prevented the ECS- or clonidine-provoked amnesia upon retention tests given 3 h, 24 h, and 7 days after training. The present data favor the view that the selective modification of 5-HT2 receptors after training can prevent the performance deficit in step-down-trained rats and suggest a role of the 5-HTergic neurotransmitter system in memory. The results of this study further suggest that 5-HTergic receptor antagonists might be useful in treatment of cognitive disorders.

Asymmetry in behavioral responses to cholecystokinin microinjected into rat nucleus accumbens and amygdala.

The behavioral responses of rats to uni- or bilateral microinjections of the octapeptide cholecystokinin (CCK-8) into the left and/or right or both nucleus accumbens (NA) or amygdalae were studied. There were two main findings of effects of microinjections of CCK-8 into NA. First, bilateral injections of CCK-8 into NA dose-dependently decreased the horizontal activity. The second more important finding was that CCK-8 at a specific dose (0.01 micrograms) injected into the right NA increased the number of horizontal movements 6-fold as compared to the injection into the left NA. Neither uni- nor bilateral injections of CCK-8 into NA at all doses used induced changes in the vertical movements. CCK-8 injected into left, right or both amigdalae increased locomotion at the lowest dose (0.01 microgram), while at the high doses (0.5 and 1.0 microgram) it significantly decreased it. The plus-maze test confirmed the anxiogenic effect of CCK-8 (0.01 microgram) injected into amigdalae. CCK-8 exerted a favorable effect on learning and memory (shuttle-box) when injected into the left but not into the right amygdala. Injection of CCK-8 (0.01 micrograms) into left amygdala provoked a 4-fold increase of the number of avoidances as compared to the microinjection into the right amygdala.

Hippocampal asymmetry in the behavioral responses to the 5-HT1A receptor agonist 8-OH-DPAT.

The present study examined the behavioral responses of rats to unilateral and bilateral injections of the selective serotonin 1A (5-HT1A)-receptor agonist 8-hydroxydipropylaminotetralin hydrobromide (8-OH-DPAT) 1 microgram into the hippocampal CA1 area of male Wistar rats. 8-OH-DPAT increased locomotor activity, which was most pronounced with injections into the left hippocampus. The agonist impaired learning and memory (shuttle-box), especially when injected into the right hippocampus. The elevated plus-maze experiments showed that neither left nor right nor bilateral hippocampal injections of 8-OH-DPAT produced any anxiogenic effect. However, with Vogel's conflict test, right injections of 8-OH-DPAT produced anxiety. The present study has revealed hippocampal asymmetry in the behavioral responses to the 5-HT1A-receptor agonist 8-OH-DPAT.

Effects of agonists and antagonists of some serotonin-receptor subtypes on memory and their modulation by the 5-HT-uptake inhibitor fluoxetine.

The memory effects of agonists and antagonists of some serotonin (5-HT)-receptor subtypes were studied in experiments on rats using the method for passive avoidance with punishment reinforcement (step-down). The 5-HT1A-receptor agonist buspirone (1 mg/kg i.p.) elicited behavioural responses which suggested the lack of pronounced effect on learning and retention; the 5-HT1A-receptor antagonists NAN-190 (1 mg/kg i.p.) and pindolol (6 mg/kg i.p.) impaired retention tested 24 hours and 7 days after training as compared to controls. The 5-HT2-receptor antagonist ritanserin (1 mg/kg i.p.) impaired retention tested 24 hours and 7 days after training as compared to controls, while the 5-HT3-receptor antagonist ondansetron (0.1 mg/kg i.p.) improved it. The 5-HT1/5-HT2-receptor antagonist dotarizine (50 mg/kg orally), characterized by a calcium-antagonistic action, too, exerted some facilitating effect on learning. Most of the effects of the 5-HT-receptor agonists and antagonists were changed when the 5-HT concentration in the synaptic region was increased by the 5-HT-uptake inhibitor fluoxetine (20 mg/kg orally). The results suggest different participation of 5-HT1A-, 5-HT2- and 5-HT3-receptors in the mechanisms of memory process and its modulation by the serotonin level in the cerebral serotonergic synapses.

Behavioral effects of the Ca2+/5-HT antagonist dotarizine.

The diphenyl-methyl-piperazine derivatives with Ca(2+)-antagonistic effect dotarizine (DOT), Fl-6020 and flunarizine were investigated in experiments on rats. The substances tested were administered repeatedly at an oral dose of 50 mg/kg. Behavioral methods were used to study the exploratory activity when the animals were placed in an environment that was unfamiliar to them (the chamber of the Opto Varimex apparatus), the elevated plus-maze method for examining the effect on anxiety, and the method of recording changes in motor activity (using the Automex II apparatus). DOT was found to increase motor activity and to have an anxiolytic effect. Combination of DOT--a compound with Ca(2+)--and 5-HT2-receptor antagonistic action--and the 5-HT-receptor agonists and antagonists used (buspirone, NAN190, pindolol, ritanserin and ondansetron) resulted in such changes in the development of habituation and in anxiety, which suggest that the modulating effects of DOT depend but partly on its typical interaction with the 5-HT2 receptor. Apparently, the Ca(2+)-antagonistic action of DOT plays a definite role, changing its biological activity depending on the 5-HT receptor subtype at the level of which the interaction is taking place.

Effects of cytidine diphosphate choline on rats with memory deficits.

The effects of cytidine diphosphate choline (CDP-choline, CAS 987-78-0) on learning and memory in rats with memory deficits were examined using behavioral methods of active avoidance with punishment reinforcement (shuttle-box), passive avoidance with punishment reinforcement (step-through and step-down), and active avoidance with positive (alimentary) reinforcement (staircase-maze). In the majority of experiments CDP-choline was applied orally at doses of 10-50 or 100 mg/kg daily for 7 days before the training session. The experiments were carried out on young-adult (aged 5 months) and old (aged 22 months) rats and on rats with a low capability for retention of learned behavior. Memory deficits were induced by the muscarinic cholinoceptor antagonist scopolamine (in young and old rats and mice), by the alpha 2-adrenoceptor agonist clonidine, by electroconvulsive shock, and by hypoxy. Memory deficits were also induced in rats offspring of dams that had been exposed to alcohol during pregnancy and lactation. The results suggest that CDP-choline acts as a memory-enhancing drug and that its effect is particularly pronounced in animals with memory deficits.

Memory effects of standardized extracts of Panax ginseng (G115), Ginkgo biloba (GK 501) and their combination Gincosan (PHL-00701).

In experiments on young (aged 3 months) and old (aged 26 months) rats, using some conditioned-reflex methods with punishment or positive reinforcement for active and passive avoidance (shuttle-box, step-down, step-through, and water maze), we studied the effects of the standardized extracts of Panax ginseng (G115), Ginkgo biloba (GK501) and their combination Gincosan (PHL-00701). The extracts were administered orally for 7 days before training at three increasing doses: 17, 50, and 150 mg/kg for G115; 10, 30, and 90 mg/kg for GK501; and 27, 80, and 240 mg/kg for PHL-00701. The two extracts and their combination improved the retention of learned behavior. This effect varied considerably with the extracts, with the dose and with the behavioral method used. The results suggest that the Panax ginseng G115 and the Ginkgo biloba GK501 extracts possess properties similar in every respect to those of nootropic drugs. The favorable effects on learning and memory of the combination of G115 plus GK501 and the other pharmacological activities inherent in the extracts characterize this combination, offered as Gincosan as a particularly promising drug in geriatric practice.

Effect of CDP-choline on learning and memory processes in rodents.

The effects of cytidine (5') diphosphocholine (CDP-choline) on learning and memory were studied using conditioned reflex methods for passive avoidance and active avoidance with punishment reinforcement (step-through, step-down, shuttle box and maze), for active avoidance with alimentary reinforcement (staircase maze), and the Morris water maze. The majority of experiments involved comparative studies of the nootropic drugs meclofenoxate and/or piracetam. CDP-choline was administered orally, in some of the experiments also intraperitoneally, at doses of 10-500 mg/kg body weight once or twice daily for 5 or 7 days. In separate cases only single doses were administered. Trainings started one hour after the last dose of the drugs. Retention tests were given 3 h, 24 h, 7 days or 10 days after training. The results obtained with the different methods document CDP-choline's ability to improve learning and memory in rats and mice. No essential differences in the effects of CDP-choline were established upon oral and intraperitoneal administration of the drug. The learning- and memory-facilitating effects of CDP-choline were similar to those of meclofenoxate and piracetam. The results of the present study permit us to define CDP-choline as a substance capable of improving cognitive levels.

[Lipid peroxidation changes in the brain in fetal alcohol syndrome]. / Izmeneniia perekisnogo okisleniia lipidov v mozge pri fetal'nom alkogol'nom sindrome.

The study was performed upon three groups of 12-week-old male rats. The first group of rats received ethanol/9 g/kg/day as 6% aqueous solution/during pregnancy and lactation, the second group received ethanol only during lactation and the third group, controls, received equicaloric sucrose solution. The concentrations of LPO products were determined in the homogenates of tissue from frontal cortex, striatum, hypothalamus, hippocamp and cerebellum. The concentration of fluorescent products in the brain structures of rats treated perinatally with ethanol was several-fold increased as compared with controls. The levels of diene conjugates were increased in most brain structures of rats with FAS. It should be pointed out that there was the same degree of increase of the levels of both fluorescent products and diene conjugates in two groups of rats with FAS. Having in mind that in the rat the increased growth of the brain occurs during the first 10 postnatal days, it might be assumed that this period is favorable for LPO.

Behavioral effects of stem-leaves extract from panax ginseng C.A. Meyer.

The behavioral effects of extracts from ginseng stem and leaves (GL), standardized with respect to the total saponines, and from ginseng roots (G115), standardized with respect to the content of ginsenosides were examined in experiments on rats with undisturbed memory and in rats with experimentally-impaired memory (electroconvulsive shock) using the methods for active avoidance (shuttle-box) and passive avoidance (step-down, step-through), the water-maze method and the method for studying exploratory behavior. On multiple administration G115 exerted favorable effects on learning and memory and on the higher nervous activity as a whole. These effects greatly varied with the dose and administration schedules, with the rat strain, with the rat's ability to perform adequately in any particular learning task, and with the behavioral method. The extract from the overground part of ginseng (GL) had, in the majority of cases, an effect weaker than that of G115 or was without effect at all. Based on previous and present results, we discuss the role of the changes in brain biogenic monoamines induced by the extracts for their mechanism of action.