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The mesolimbic dopamine system, the main neural system mediating sensitization, seems to overlap this mediating reward. Given some data indicating that dopamine neurons are effected by cholinergic neurotransmitters, the aim of present study was to determine the influence of varenicline, a partial α4β2 nicotinic receptor agonist (0.5, 1 and 2 mg/kg) and mecamylamine, a nonselective nicotinic receptor antagonist (0.5, 1 and 2 mg/kg) on behavioural sensitization and cross – sensitization induced by nicotine (0.175 mg/kg, base) and morphine (5 mg/kg) in mice. First, we revealed that repeated injections of nicotine (9 days, every other day) produced significant increase in locomotor activity in mice measured following 7-day withdrowal after injection of challange doses of nicotine and morphine. Subsequently, we found that varenicline and mecamylamine attenuated the acquisition and expression of nicotine sensitization as well as locomotor crosssensitization between nicotine and morphine. Because they had no effects on naive mice, we concluded that the ability of both agents to block this results did not correspond to general supression of activity. The development of nicotine locomotor sensitization shows similarity to relapse described in ex-smokers and cross – sensitization seems to reflect the phenomenon of simultaneous abuse of several different drugs. Our results indicate similar nicotinic neurotransmission - probably through the α4β2 receptor subtypes - involved in the locomotor stimulant effects of nicotine and morphine in mice. This data suggest that cholinergic neurotransmission may be a potential target for developing pharmacotherapeutic strategies to prevent and treat nicotine and/or opioid addiction.
INTRODUCTION: The endocannabinoid system (ECS) is composed of cannabinoid (CB: CB1 and CB2) receptors and endocannabinoids, which are degraded by fatty acid hydrolase (FAAH) and monoacylglycerol lipase (MAGL). Thus, the function of the ECS might be modulated in a direct way, through CB receptor ligands or indirectly by FAAH and MAGL inhibitors. The ECS system is involved in many physiological functions, also through interaction with many systems. The cholinergic system plays a crucial role in memory processes. A connection with the ECS, especially CB and cholinergic receptor ligands, is supported by a large body of research. However, the influence of the ECS through an indirect manner in the context of cognitive processes remains poorly understood. AIM(S): The aim of the study was to evaluate the indirect influence of ECS, using of FAAH (URB 597) and MAGL (JZL 184) inhibitors, on memory related effects provoked by cholinergic receptor ligands, a cholinergic receptor agonist, nicotine, and a cholinergic receptor antagonist, scopolamine, in mice. METHOD(S): We assessed different memory stages using the passive avoidance (PA) test. A deficit in PA performance was expressed as the difference between retention and training latencies and is taken as an index of latency (IL). RESULTS: Co-administration of non-effective dose of JZL 184 (4 mg/kg), but not URB 597 (0.1 mg/kg), with a non‑effective dose of nicotine (0.05 mg/kg) enhanced both acquisition and consolidation of memory in the PA test in mice. An acute injection of JZL 184 (4 mg/kg) attenuated pro‑cognitive effects induced by effective dose of nicotine (0.1 mg/kg). In turn, co‑administration of URB (0.1 mg), but not JZL 184 (4 mg/kg), with scopolamine (1 mg/kg) attenuated the scopolamine-induced memory impairment in the PA test in mice CONCLUSIONS: The present findings clearly indicate that the ECS, through an indirect manner, modulates memory processes, especially those in which cholinergic pathways are implicated.
The aim of present experiments was to investigate the influence of cholinergic receptor’s ligands on memory-related behavior in mice, using the elevated plus maze (EPM) test. This test allows examining different processes of memory (acquisition and consolidation), depending on the time of drug treatment. The time 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. We revealed that in both processes of acquisition and consolidation, nicotine (0.035 and 0.175 mg/kg, free base, sc) shortened TL on the second day of experiment (TL2), improving memory processes. In contrast, scopolamine (0.3 and 1.0 mg/kg, ip) significantly increased TL2 values, impairing cognitive processes. In the following experiments, we evaluated the influence of a drug currently used in smoking cessation in humans, bupropion, on memoryrelated behavior induced by nicotine and scopolamine. Interestingly, the acute injection of bupropion (10 and 20 mg/ kg), prior to injections of both nicotine (0.035 mg/kg) or scopolamine (1.0 mg/kg), significantly prevented nicotine-induced memory improvement or scopolamine-induced memory impairment. Bupropion can diminish not only the rewarding (dependence-producing) effects of nicotine, but also its cognitive effects related to addiction. Our studies further indicated the great involvement of the cholinergic system in memory and allow development of more effective pharmacotherapies for memory impairment-like treatment of human disorders in which cholinergic pathways can be implicated.
3,4-Methylenedioxymethamphetamine (MDMA, ‘ecstasy’), a potent monoamine-releaser that is widely used as a recreational drug. Hence, understanding the effects and mechanisms of MDMA is of immense importance for the public health in the world. We examined how an acute dose of MDMA affects memory and learning processes, anxiety- and depressive-like behaviors in female Swiss mice as well as oxidative processes in brain. The aim of the present study was to examine the effects of MDMA (20–0.1 mg/kg, ip) in the forced swim test (FST), elevated plus maze (EPM) and passive avoidance (PA) paradigm in mice. At first, we showed that MDMA at the doses of 10 and 2.5 mg/kg exhibited a significant reduction of immobility time in the FST, indicating the antidepressant-like activity. In the second series of our experiment, we demonstrated that MDMA at the doses of 5 and 2.5 mg/kg improved consolidation of memory processes in PA test. Also, this compound showed strong anxiogenic effect at the range of doses (20–0.5 mg/kg). MDMA at the higher doses (20-5 mg/kg) enhanced oxidative stress, expressed as superoxide dismutase activity, ascorbic acid concentration and malondialdehyde level, within brain, whereas its lower doses did not affect measured parameters. Taken together, these data suggest an anxiogenic-like, antidepresive and procognitive in consolidation trial effects of acute MDMA treatment. The results of our study also showed the influence of MDMA on the oxidative stress processes in the brain.
The purpose of the experiments was to examine the anxiety-related effects of d-amphetamine and nicotine, and the possible involvement of the endocannabinoid system. D-amphetamine (2 mg/kg, ip) was administered acutely or daily for 8 days. On the 9th day, mice were challenged with d-amphetamine (2 mg/kg, ip) or nicotine (0.1 mg/kg, sc), and were tested in the elevated plus maze. Additionally, a distinct group of mice was pretreated with an acute (0.1 mg/kg, sc) or subchronic nicotine (6 days), and subjected to nicotine (0.1 mg/kg, sc) or d-amphetamine (2 mg/kg, ip) challenge on the 7th day. The cannabinoid receptor ligands, WIN 55,212-2, a non-selective cannabinoid receptor agonist (0.25; 0.5 and 1 mg/kg, ip) and rimonabant, a CB1 cannabinoid receptor antagonist (0.25; 0.5; 1 and 2 mg/kg, ip) were injected prior to each injection of saline or acute and subchronic d-amphetamine or nicotine. We observed that acute anxiogenic and subchronic anxiolytic effects of both psychostimulants as well as the development of full cross-tolerance to their anxiogenic effects were dose-dependently blunted by ineffective doses of WIN 55,212-2 (0.25 and 0.5 mg/kg) and rimonabant (0.5 and 1 mg/kg). These results provide evidence that the endogenous cannabinoid system is involved in the anxiety-related responses to d-amphetamine and/or nicotine.
Cannabinoids are implicated in regulation of variety emotions through the type 1 (CB1) and type 2 (CB2) receptors. Our pharamcological interests have been focused on the effects of CB2 receptor selective ligands in the treatment of Alzheimer disease (AD) which is associated with memory-loss, phobia, depression as well as oxidative processes in brain. We examined the impact of CB2 agonist: JWH-133 in mice using passive avoidance (PA) test to measure memory-related responses, elevated plus maze (EPM) test to measure anxiety-related behavior and forced swimming test (FST) to measure depression-related responses. Total antioxidant capacity (TAC) and lipids peroxidation level, expressed as malondialdehyde (MDA) concentration, were measured in homogenates of brain. Our findings revealed that a single injection of JWH-133 improved memory in PA, had an anxiogenic effects in EPM, antidepressant effects in FST and slightly increased total antioxidant capacity but did not affect lipids peroxidation level in brain. CB2 ligands could become a new pharmacological alternative in treatment of AD which is associated not only with emotional-related disorders but also with oxidative stress.
A common element in the phenomenon of addiction is polydrug abuse. Behavioural responses related to the relapse to drug taking can be measured in various animal models e.g., in the conditioned place preference (CPP) paradigm. In the present experiments, we employed CPP paradigm including the establishment, extinction, reinstatement and cross-reinstatement procedures, to study mechanisms of nicotine seeking behaviour and interactions between nicotine and cannabinoids and ethanol. First, we revealed that nicotine produced a place preference to the initially less-preferred compartment paired with its injections during conditioning (0.175 mg/kg, base, i.p.). Once established, nicotine CPP was extinguished by repeated testing. Following this extinction phase, nicotineexperienced rats were challenged with CB1 receptor agonist – WIN 55,212-2 (0.5 mg/kg, i.p.) or ethanol (0.5 g/kg, i.p.). These priming injections of both drugs reinstated a marked preference for the compartment previously paired with nicotine. Furthermore, we evaluated the efficacy of atypical antidepressant drug - bupropion (5, 10 and 20 mg/kg, i.p.) in blocking reinstatement of nicotine CPP provoked by WIN 55,212-2 and ethanol. Our results demonstrated that bupropion (exept for dose 10 mg/kg used in reinstatement induced by WIN 55,212-2) attenuated the reinstatement of nicotine-conditioned response induced by both drugs. Results obtained in the present studies may contribute to better understanding of the neurochemical mechanisms underlying nicotine addiction and reciprocal relationships between nicotine, cannabis and ethanol. As reinstatement of drug-seeking is a factor for the development of dependence, bupropion may be useful in the relapse-prevention phase of addiction treatment.
Reinstatement of drug-seeking behaviour in animals is relevant to relapse to drug taking in humans. In the present study, we used the conditioned place preference paradigm to investigate the establishment, extinction, reinstatement and cross-reinstatement of nicotine-induced place conditioning in rats. We have revealed that nicotine produced a place preference to the compartment paired with its injections during conditioning. Once established, nicotine place preference was extinguished by repeated testing. Following this extinction phase, nicotine-experienced rats were challenged with nicotine (0.5 mg/kg) or morphine (10 mg/kg). These priming injections of both drugs renewed a marked preference for the compartment previously paired with nicotine. In the second step, we examined the infl uence of CB1 cannabinoid receptor antagonist rimonabant (0.5, 1 and 2 mg/kg) on the reinstatement of nicotine place conditioning. It was shown that rimonabant, dosedependently, attenuated the reinstatement of nicotine-conditioned response. Our fi ndings may further indicate similar endocannabinoid-dependent mechanisms involved in the development of reinstatement of nicotine-conditioned place preference provoked by priming injections of nicotine and morphine. As reinstatement of drug-seeking is a factor for the development of drug dependence, CB1 receptor antagonists may be useful in the relapse-prevention phase of addiction treatment, including nicotinism and polydrug abuse.
INTRODUCTION: Posttraumatic stress disorder (PTSD) is a chronic and prevalent psychiatric condition that may develop following exposure to traumatic events. Depressive symptoms and anxiety belong to the most frequent symptoms observed in PTSD patients. Less than 30% of PTSD patients achieve full remission with the use of available drugs. For this purpose, there is a clear need to develop more efficient and safer drugs as alternative and/or complimentary therapy for PTSD. Hyperoside (HYP) is one of the polyphenols found in Impatiens glandulifera. Our previous experiments showed that HYP exerted antidepressant effects, both after acute and chronic (14 days) treatment in mice in the forced swimming test (FST; data not published). AIM(S): The present study aimed to investigate the effect of HYP on the behavioural impairments (depression and anxiety) induced by a mouse single prolonged stress (mSPS) – a rodent model of PTSD. METHOD(S): mSPS protocol: mice were exposed to a series of short stressors. In particular, they were restrained for 2 h in a Plexiglas tubes (50 ml), placed in glass beakers and immersed in water (23‑25°C) for a group swim (10 min). Then, they were exposed to a beaker of soiled bedding taken from cages of rats (15 min), and at the end, they were exposed to anhydrous diethyl ether until they lost consciousness (approx. 2 – 3 min). Seven days after exposure to SPS, the administration of substances was started (during next 14 days). Then, animals were subjected to behavioural tests, including the elevated plus-maze test (EPM), measurement of locomotion, and FST. RESULTS: Mice given chronically HYP (3.75 and 7.5 mg/kg) after exposure to mSPS exhibited a reduction of immobility time in FST, and more open arm entries and longer open arms duration in EPM without affecting locomotor activity as compared to control‑mSPS group. CONCLUSIONS: In summary, our results suggested the potential of HYP in alleviating the mSPS-induced depressive and anxiety‑like responses.
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