Marta Kruk-Slomka

Effects of imperatorin on scopolamine-induced cognitive impairment and oxidative stress in mice

RationaleImperatorin, a naturally occurring furanocoumarin, inactivates gamma-aminobutyric acid transaminase and inhibits acetylcholinesterase activity.ObjectivesThe purpose of our experiment was to examine the influence of imperatorin on cognitive impairment and oxidative stress in the brain induced by scopolamine in male Swiss mice.MethodsIn the present studies, we used scopolamine-invoke memory deficit measured in passive avoidance (PA) paradigm as an animal model of Alzheimer disease (AD).ResultsOur finding revealed that imperatorin administered acutely at the doses of 5 and 10 mg/kg prior to the injection of scopolamine (1 mg/kg) improved memory acquisition and consolidation impaired by scopolamine. Furthermore, repeatable (7 days, twice daily) administration of the highest dose of imperatorin (10 mg/kg) significantly attenuated the effects of scopolamine on memory acquisition, whereas the doses of 5 and 10 mg/kg of this furanocoumarin were effective when memory consolidation was measured. Imperatorin, administered with scopolamine, increased antioxidant enzymes activity and decreased concentration of malondiamide, an indicator of lipid peroxidation level.ConclusionsThese results demonstrate that imperatorin may offer protection against scopolamine-induced memory impairments and possesses antioxidant properties, thus after further preclinical and clinical studies this compound may provide an interesting approach in pharmacotherapy, as well as prophylactics of AD.

Effects of imperatorin on nicotine-induced anxiety- and memory-related responses and oxidative stress in mice.

The purpose of the reported experiments was to examine the effects of imperatorin [9-[(3-methylbut-2-en-1-yl)oxy]-7H-furo[3,2-g]chromen-7-one] on anxiety and memory-related responses induced by nicotine in mice and their relation to the level of nicotine-induced oxidative stress in brain as well as in the hippocampus and the prefrontal cortex. Male Swiss mice were tested for anxiety in the elevated plus maze test (EPM), and for cognition using passive avoidance (PA) procedures. Imperatorin, purified by high-speed counter-current chromatography from methanol extract of fruits of Angelica officinalis, acutely administered at the doses of 10 and 20mg/kg impaired the anxiogenic effect of nicotine (0.1mg/kg, s.c.). Furthermore, acute injections of subthreshold dose of imperatorin (1mg/kg, i.p.) improved processes of memory acquisition when co-administered with nicotine used at non-active dose of 0.05 mg/kg, s.c. Additionally, repeated administration of imperatorin (1mg/kg, i.p., twice daily, for 6 days) improved different stages of memory processes (both acquisition and consolidation) when injected in combination with non-active dose of nicotine (0.05 mg/kg, s.c.) in the PA task. Oxidative stress was assessed by determination of antioxidant enzymes (glutathione peroxidases (GPx), superoxide dismutase (SOD), glutathione reductase (GR)) activities as well as of malondialdehyde (MDA) concentration in the whole brain, the hippocampus and the prefrontal cortex after repeated administration of imperatorin (1mg/kg, 6 days) and single nicotine injection (0.05 mg/kgs.c.) on the seventh day. The results of our research suggest strong behavioural interaction between imperatorin and nicotine at the level of anxiety- and cognitive-like processes. Furthermore, imperatorin inhibited nicotine-induced changes in examined indicators of oxidative stress, especially in the hippocampus and the cortex.

Antidepressant-like effects of the cannabinoid receptor ligands in the forced swimming test in mice: mechanism of action and possible interactions with cholinergic system.

The purpose of the experiments was to explore the role of the endocannabinoid system, through cannabinoid (CB) receptor ligands, nicotine and scopolamine, in the depression-related responses using the forced swimming test (FST) in mice. Our results revealed that acute injection of oleamide (10 and 20 mg/kg), a CB1 receptor agonist, caused antidepressant-like effect in the FST, while AM 251 (0.25-3 mg/kg), a CB1 receptor antagonist, did not provoke any effect in this test. Moreover, acute administration of both CB2 receptor agonist, JWH 133 (0.5 and 1 mg/kg) and CB2 receptor antagonist, AM 630 (0.5 mg/kg), exhibited antidepressant action. Antidepressant effects of oleamide and JWH 133 were attenuated by acute injection of both non-effective dose of AM 251, as well as AM 630. Among the all CB compounds used, only the combination of non-effective dose of oleamide (2.5 mg/kg) with non-effective dose of nicotine (0.5 mg/kg) caused an antidepressant effect. However, none of the CB receptor ligands, had influence on the antidepressant effects provoked by nicotine (0.2 mg/kg) injection. In turn, the combination of non-effective dose of oleamide (2.5 mg/kg); JWH (2 mg/kg) or AM 630 (2 mg/kg), but not of AM 251 (0.25 mg/kg), with non-effective dose of scopolamine (0.1 mg/kg), exhibited antidepressant properties. Indeed, all of the CB compounds used, intensified the antidepressant-like effects induced by an acute injection of scopolamine (0.3 mg/kg). Our results provide clear evidence that the endocannabinoid system participates in the depression-related behavior and through interactions with cholinergic system modulate these kind of responses.

Involvement of cholinergic receptors in the different stages of memory measured in the modified elevated plus maze test in mice

BACKGROUND AND METHODS Several lines of evidence support a strong relationship between cholinergic pathways and memory. The aim of our experiments was to examine the mechanisms involved in the formation of different memory stages, to evaluate the impact of substances, which affect the cholinergic system in mice, with an employment of the modified elevated plus maze (mEPM) test. This test allows examining different processes of memory (acquisition, consolidation and retrieval), depending on the time of drug treatment. The time period, necessary for mice to move from the opened arm to the enclosed arm (i.e., transfer latency, TL) was used as an index of memory. RESULTS Our findings revealed that in both memory acquisition and consolidation, nicotine, an agonist of cholinergic receptors (0.035 and 0.175 mg/kg, free base, sc), reduced TL on the second day of the experiment (TL2), thus improving memory. In turn, scopolamine, an antagonist of cholinergic receptors (0.3 and 1.0 mg/kg, ip), significantly increased TL2 values, impairing cognition. Subsequently, we evaluated the influence of mecamylamine, a non-selective antagonist of nicotinic cholinergic receptors (nAChRs) and of varenicline, an a4b2 partial nAChRs agonist, on memory-related behaviors induced by nicotine and scopolamine. Acute injections of mecamylamine (0.5 and 1.0 mg/kg, ip) and varenicline (0.5 and 1.0 mg/kg, ip), prior to the injections of nicotine (0.035 mg/kg) or scopolamine (1.0 mg/kg), significantly suppressed nicotine-induced memory improvement or scopolamine-induced memory impairment. CONCLUSION Our studies indicate that the cholinergic system plays a crucial role in memory processes. Pharmacological manipulation of cholinergic transmission can be the base to develop more effective pharmacotherapies for these memory disturbances in which cholinergic receptors are involved.

The effects of imperatorin on anxiety and memory-related behavior in male Swiss mice.

The purpose of the reported experiments was to examine the effects of imperatorin [9-(3-methylbut-2-enyloxy)-7H-furo[3,2-g]chromen-7-one], a bioactive furanocoumarin isolated from the fruits of Angelica archangelica (Angelica officinalis) on anxiety and memory-related behaviors of mice. Male Swiss mice were tested for anxiety and cognition, in the elevated plus maze test (EPM), using two different procedures. In the present experiments, imperatorin was administered acutely (at the doses of 5, 10, 20, 30, and 50 mg/kg); injections were made 15, 30, and 60 min before test (anxiety); 30 min before the first trial (memory acquisition); or immediately after the first trial (memory consolidation), as well as subchronically, twice a day for 6 days. On the seventh day, the mice were injected once with imperatorin (10 and 20 mg/kg, i.p.) 30 min before the test (anxiety) and 30 min before the first trial (memory acquisition), or immediately after the first trial (memory consolidation). We observed that imperatorin when administered acutely and repeatedly, at the doses of 10 and 20 mg/kg, exerted an anxiolytic effect on mice tested 30 min after the injection measured in the EPM test. By contrast, no such effect was observed after the acute administration of imperatorin at the doses of 5, 30 and 50 mg/kg. Moreover, other observations carried out 15 and 60 min after a single injection of the drug did not reveal any effect of imperatorin on anxiety behavior in the EPM test. Furthermore, acute and repeated administration of imperatorin (10 and 20 mg/kg) improved different stages of memory processes (both acquisition and consolidation) in a modified EPM test (mEPM). The results of our research suggest imperatorin to be an interesting therapeutical option in disorders with high anxiety levels and memory impairment.

A comparison of mecamylamine and bupropion effects on memory-related responses induced by nicotine and scopolamine in the novel object recognition test in mice

BACKGROUND The aim of the present study was to evaluate the involvement of the cholinergic receptors ligands in the memory-related responses in mice, using the novel object recognition (NOR) test. METHODS The NOR test is based on natural, exploratory abilities of animals exposed to a new environment. In the first session, two copies of the same object were presented. In the next sessions (30min and 24h after), one of the familiar object and a new object were presented. RESULTS The mice injected with nicotine (0.035 and 0.175mg/kg, free base, sc) before the first session spent more time exploring the new object than the familiar one at the second and third session, indicating that nicotine improved cognition. In turn, the mice injected with scopolamine (0.3 and 1mg/kg, ip) before the first session spent less time exploring the new object than the familiar one at the second and third trial, indicating that scopolamine impaired the memory performance. Additionally, the acute injection of drugs used in smoking cessation in humans: mecamylamine (0.5 and 1mg/kg) and bupropion (5 and 10mg/kg), prior to injections of nicotine (0.035mg/kg) or scopolamine (1mg/kg), significantly prevented nicotine-induced memory improvement or scopolamine-induced memory impairment, at the second and third session. CONCLUSIONS The results of our studies unveiling neuronal mechanisms for cholinergic system of memory processes, via both nicotinic and muscarinic cholinergic receptors, will be useful for development of more effective pharmacotherapies for memory impairment-like treatment of human disorders in which cholinergic pathways have been implicated.

Correlations between the Memory-Related Behavior and the Level of Oxidative Stress Biomarkers in the Mice Brain, Provoked by an Acute Administration of CB Receptor Ligands

The endocannabinoid system, through cannabinoid (CB) receptors, is involved in memory-related responses, as well as in processes that may affect cognition, like oxidative stress processes. The purpose of the experiments was to investigate the impact of CB1 and CB2 receptor ligands on the long-term memory stages in male Swiss mice, using the passive avoidance (PA) test, as well as the influence of these compounds on the level of oxidative stress biomarkers in the mice brain. A single injection of a selective CB1 receptor antagonist, AM 251, improved long-term memory acquisition and consolidation in the PA test in mice, while a mixed CB1/CB2 receptor agonist WIN 55,212-2 impaired both stages of cognition. Additionally, JWH 133, a selective CB2 receptor agonist, and AM 630, a competitive CB2 receptor antagonist, significantly improved memory. Additionally, an acute administration of the highest used doses of JWH 133, WIN 55,212-2, and AM 630, but not AM 251, increased total antioxidant capacity (TAC) in the brain. In turn, the processes of lipids peroxidation, expressed as the concentration of malondialdehyde (MDA), were more advanced in case of AM 251. Thus, some changes in the PA performance may be connected with the level of oxidative stress in the brain.

Endocannabinoid System: the Direct and Indirect Involvement in the Memory and Learning Processes—a Short Review

The endocannabinoid system via cannabinoid (CB: CB1 and CB2) receptors and their endogenous ligands is directly and indirectly involved in many physiological functions, especially in memory and learning processes. Extensive studies reported that this system strictly modulates cognition-related processes evaluated in various animal models. However, the effects of cannabinoids on the cognition have been contradictory. The cannabinoid compounds were able to both impair or improve different phases of memory processes through direct (receptor related) or indirect (non-receptor related) mechanism. The memory-related effects induced by the cannabinoids can be depended on the kind of cannabinoid compound used, dosage, and route of administration as well as on the memory task chosen. Therefore, the objectives of this paper are to review and summarize the results describing the role of endocannabinoid system in cognition, including various stages of memory.

Influence of calcium channel antagonists on nonsomatic signs of nicotine and d-amphetamine withdrawal in mice

BACKGROUND Nonsomatic signs of psychostimulant withdrawal, difficult to demonstrate in animal paradigms, may appear to promote drug seeking and drug relapse in humans; thus, it is important to understand the mechanisms that mediate this kind of behaviors. The present study was undertaken to examine the calcium-dependent mechanism of negative nonsomatic and anhedonia-related symptoms of acute and protracted withdrawal of nicotine and D-amphetamine. METHODS Mice were chronically treated with nicotine (seven days, three times daily, 3.35 mg/kg, sc) or D-amphetamine (14 days, once daily, 2.5mg/kg, ip). Then, at the first, seventh or 14th day of withdrawal, anxiety- or depression-related effects, as well as cognition or nociception were studied. RESULTS Our results demonstrated that, at the seventh or 14th day of D-amphetamine or nicotine withdrawal, respectively, mice exhibited increased anxiety and depression-like effects, memory impairment and hyperalgesia. Further, major findings showed that calcium channel antagonists, i.e., nimodipine, verapamil and flunarizine (10 and 20mg/kg, ip), injected before the test, attenuated above-mentioned signs of drug withdrawal. CONCLUSIONS As an outcome, these findings support the hypothesis that similar calcium-dependent mechanisms are involved in an aversive nonsomatic component, associated with nicotine or d-amphetamine withdrawal. We can suggest that calcium channel blockers have potential to alleviate drug withdrawal and may thus be beneficial as pharmacotherapy of drug cessation and relapse.

CB1 receptors in the formation of the different phases of memory-related processes in the inhibitory avoidance test in mice

The endocannabinoid system, through the cannabinoid type 1 (CB1) and 2 (CB2) receptors modulates many physiological functions, including different aspects of memory-related processes. The aim of the present experiments was to explore the role of the endocannabinoid system, through CB1 receptors in the different stages of short-term (acquisition, retention and retrieval) and long-term (acquisition, consolidation and retrieval) memory-related responses, using the inhibitory avoidance (IA) test in mice. Our results revealed that an acute injection of oleamide (10 and 20mg/kg), a CB1 receptor agonist, impairs the short-term or/and long-term acquisition, retention/consolidation, retrieval memory and learning processes in the IA test in mice. In turn, in this test an acute injection of AM 251 (1 and 3mg/kg), a CB1 receptor antagonist, improves the short-term or/and long-term memory stages, described above. Moreover, this memory impairment induced by effective dose of oleamide (20mg/kg) is reversed by non-effective dose of AM 251 (0.25mg/kg) in the IA task, which proves the selectivity of oleamide to CB1 receptors and confirms that the CB1 receptor-related mechanism is one of the possible mechanisms, responsible for memory and learning responses. Obtained results provide clear evidence that the endocannabinoid system, through CB1 receptors, participates in the different stages of short- and long-term memory-related behavior. This knowledge may open in the future new possibilities for the development of CB-based therapies, especially for memory impairment human disorders.