Agnieszka Michalak

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.

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.

Calcium homeostasis and protein kinase/phosphatase balance participate in nicotine-induced memory improvement in passive avoidance task in mice.

HighlightsNicotine enhances memory via L‐type VGCC blockade and via ERK1/2 activation.Only short‐term memory enhancement induced by nicotine is dependent on CaN inhibition.Nicotine affects short‐ and long‐term memory via similar cell signaling substrates. ABSTRACT Long‐term potentiation (LTP) and long‐term depression (LTD) depend on specific postsynaptic Ca2+/calmodulin concentration. LTP results from Ca2+ influx through the activated NMDA receptors or voltage‐gated calcium channels (VGCCs) and is linked with activation of protein kinases including mitogen‐activated protein kinase (MAPK). Weaker synaptic stimulation, as a result of low Ca2+ influx, leads to activation of Ca2+/calmodulin‐dependent phosphatase (calcineurin – CaN) and triggers LTD. Interestingly, both memory formation and drug addiction share similar neuroplastic changes. Nicotine, which is one of the most common addictive drugs, manifests its memory effects through nicotinic acetylcholine receptors (nAChRs). Because nAChRs may also gate Ca2+, it is suggested that calcium signaling pathways are involved in nicotine‐induced memory effects. Within the scope of the study was to evaluate the importance of calcium homeostasis and protein kinase/phosphatase balance in nicotine‐induced short‐ and long‐term memory effects. To assess memory function in mice passive avoidance test was used. The presented results confirm that acute nicotine (0.1 mg/kg) improves short‐ and long‐term memory. Pretreatment with L‐type VGCC blockers (amlodipine, nicardipine verapamil) increased nicotine‐induced memory improvement in the context of short‐ and long‐term memory. Pretreatment with FK‐506 (a potent CaN inhibitor) enhanced short‐ but not long‐term memory effects of nicotine, while SL‐327 (a selective MAPK/ERK kinase inhibitor) attenuated both nicotine‐induced short‐ and long‐term memory improvement. Acute nicotine enhances both types of memory via L‐type VGCC blockade and via ERK1/2 activation. Only short‐ but not long‐term memory enhancement induced by nicotine is dependent on CaN inhibition.

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.

Acute behavioral effects of co-administration of mephedrone and MDMA in mice

BACKGROUND Abuse of more than one psychoactive drug is becoming a global problem. Our experiments were designed to examine the effects of a concomitant administration of 3,4-methylenedioxy-methamphetamine (MDMA) and mephedrone on depression- and anxiety-like behaviors and cognitive processes in Swiss mice. METHODS In order to investigate the drug interactions the forced swimming test (FST) - an animal model of depression, the passive avoidance (PA) test - a memory and learning paradigm, as well as the elevated plus maze (EPM) test - test for anxiety level were used. RESULTS The results revealed that a concomitant administration of non-effective doses of mephedrone (1mg/kg) and MDMA (1mg/kg) exerted marked antidepressive effects in the FST. Also a co-administration of mephedrone (2.5mg/kg) and MDMA (1mg/kg) displayed a pro-cognitive action in the PA paradigm. Furthermore, even though mephedrone and MDMA can, in general, exert some anxiogenic effects in mice, the concomitant administration of nonactive doses of both drugs (0.05 and 0.1mg/kg, respectively) in the EPM test, did not show any synergistic effect in our study. CONCLUSIONS The effects of mephedrone and MDMA combination on mammalian organisms were attempted to be evaluated in our study and the results are described in the present report. These results may help explain the reasons for and consequences of a concomitant administration of psychoactive substances with regards to the central nervous system, while being possibly useful in the treatment of polydrug intoxication.

Impacts of cannabinoid receptor ligands on nicotine- and chronic mild stress-induced cognitive and depression-like effects in mice.

HighlightsCMUS caused depression‐like behaviors and memory disturbances in mice.Nicotine alleviated stress‐induced behavioral changes in stressed mice.CB receptor ligands decreased effects of subchronic nicotine in stressed mice.CB1 and CB2 receptors are engaged in stress‐ and nicotine‐related behavioral changes. ABSTRACT Taking into account the rather frequent concomitance of nicotine abuse and stress, we aimed to research memory‐ and depression‐related effects of nicotine administration in combination with chronic mild unpredictable stress (CMUS) in mice and an involvement of the endocannabinoid system through CB1 and CB2 receptors. Mice were submitted to the CMUS for 4 weeks. Effects on depression‐like behaviors and cognition, exerted by a combined administration of CB1, i.e., Oleamide (2.5, 5.0 mg/kg), AM 251 (0.1, 0.25 mg/kg) and CB2, i.e., JWH 133 (0.5, 2.0 mg/kg), AM 630 (0.25, 2.0 mg/kg) receptor ligands and nicotine (0.05, 0.1, 0.2 and 0.5 mg/kg), were then studied in stressed and unstressed mice by the forced swimming test and the passive avoidance paradigm, respectively. The results revealed that the CMUS‐exposed mice exhibited depression‐like behaviors and memory disturbances, while both effects were alleviated by nicotine. CB1 receptor ligands decreased antidepressive and cognitive (the latter for CB1 receptor antagonist only) effects of subchronic nicotine administration in stressed mice. CB1 and CB2 receptor antagonists exerted themselves some procognitive effects in those mice. Regarding the unstressed mice, CB1 and CB2 receptor ligands reversed the antidepressive effects of subchronic nicotine administration, while nicotine, in an ineffective dose, co‐administered with CB2 receptor ligands, improved cognition. We confirmed the role of the two main subtypes of cannabinoid receptors, termed CB1 and CB2, on stress‐ and nicotine‐related behavioral changes in mice. Our study has contributed to the understanding of the mechanisms involved in stress‐ and nicotine‐induced disorders, such as anhedonia and memory disturbances.

The role of verapamil and SL-327 in morphine- and ethanol-induced state-dependent and cross state-dependent memory

ABSTRACT Drugs of abuse trigger a very specific type of memory called state‐dependent memory (SDM). Both memory process and drug addiction are underlain by neuroplasticity, which depends on calcium concentration and protein kinase activity. Within the scope of this study was to evaluate the impact of verapamil, an L‐type voltage‐gated calcium channel (VGCC) blocker, and SL‐327, a selective MAPK/ERK kinase inhibitor, on morphine and ethanol SDM including the cross effects between these drugs with an additional influence of nicotine. To assess SDM in mice a step‐through passive avoidance task was used. Our results show that amnestic effects of morphine (10.0mg/kg, s.c.) and ethanol (1.0g/kg, i.p.) can be reversed by pre‐test administrations of morphine (10.0mg/kg, s.c.), ethanol (1.0g/kg, i.p.) and nicotine (0.1mg/kg, s.c.), indicating morphine and ethanol SDM, as well as morphine‐ethanol, morphine‐nicotine, ethanol‐morphine and ethanol‐nicotine cross SDM. Pre‐test co‐treatment of verapamil (10.0mg/kg, i.p.) with morphine/ethanol/nicotine increased all investigated SDM and cross SDM effects. Pre‐test co‐treatment of SL‐327 (10.0mg/kg, i.p.) diminished morphine‐ and ethanol‐induced SDM along with the cross effects except ethanol‐morphine cross SDM. In conclusion, SDM depends on ERK1/2 activation and also verapamil affects this type of memory, although the exact mechanism of its cognitive action has not been investigated in this study.