Influence of bupropion and calcium channel antagonists on the nicotine-induced memory-related response of mice in the elevated plus maze in mice

Targeting Calcium Homeostasis in Myocardial Ischemia/Reperfusion Injury: An Overview of Regulatory Mechanisms and Therapeutic Reagents

Calcium homeostasis plays an essential role in maintaining excitation–contraction coupling (ECC) in cardiomyocytes, including calcium release, recapture, and storage. Disruption of calcium homeostasis may affect heart function, leading to the development of various heart diseases. Myocardial ischemia/reperfusion (MI/R) injury may occur after revascularization, which is a treatment used in coronary heart disease. MI/R injury is a complex pathological process, and the main cause of increased mortality and disability after treatment of coronary heart disease. However, current methods and drugs for treating MI/R injury are very scarce, not ideal, and have limitations. Studies have shown that MI/R injury can cause calcium overload that can further aggravate MI/R injury. Therefore, we reviewed the effects of critical calcium pathway regulators on MI/R injury and drew an intuitive diagram of the calcium homeostasis pathway. We also summarized and analyzed calcium pathway-related or MI/R drugs under research or marketing by searching Therapeutic Target and PubMed Databases. The data analysis showed that six drugs and corresponding targets are used to treat MI/R injury and involved in calcium signaling pathways. We emphasize the relevance of further detailed investigation of MI/R injury and calcium homeostasis and the therapeutic role of calcium homeostasis in MI/R injury, which bridges basic research and clinical applications of MI/R injury.

Differential effects of bupropion on acquisition and performance of an active avoidance task in male mice

Bupropion is an antidepressant drug that is known to aid smoking cessation, although little experimental evidence exists about its actions on active avoidance learning tasks. Our aim was to evaluate the effects of this drug on two-way active avoidance conditioning. In this study, NMRI mice received bupropion (10, 20 and 40mg/kg) or saline before a daily training session (learning phase, days 1-4) in the active avoidance task. Performance was evaluated on the fifth day (retention phase): in each bupropion-treated group half of the mice continued with the same dose of bupropion, and the other half received saline. Among the vehicle-treated mice, different sub-groups were challenged with different doses of bupropion. Results indicated that mice treated with 10 and 20mg/kg bupropion exhibited more number of avoidances during acquisition. The response latency confirmed this learning improvement, since this parameter decreased after bupropion administration. No differences between groups were observed in the retention phase. In conclusion, our data show that bupropion influences the learning process during active avoidance conditioning, suggesting that this drug can improve the control of emotional responses.

Enhancement of nootropic effect of duloxetine and bupropion by caffeine in mice

Objective:

The existing evidence suggests an association between depression and memory impairment. The objective of present study was to assess the effect of low dose caffeine with duloxetine and bupropion on memory.

Materials and Methods:

Mice were divided randomly into seven groups. Intra-peritoneal treatment of normal saline (10 ml/kg), caffeine (10 mg/kg), duloxetine (10 mg/kg), bupropion alone (10 mg/kg), caffeine + duloxetine (5 mg/kg, each), caffeine + bupropion (5 mg/kg, each), and bupropion + duloxetine (5 mg/kg, each) were given to groups I-VII, respectively. Elevated plus maze was used to evaluate transfer latency (TL) and Morris water maze was used to estimate the time spent in target quadrant.

Results:

Caffeine with duloxetine treated group was better than other combination treated groups in terms of a significant decrease in TL and increase in the time spent in target quadrant recorded.

Conclusion:

Combining lower dose of caffeine with duloxetine may enhance cognitive benefits than respective monotherapies.

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.

The ClockΔ19 mutation in mice fails to alter the primary and secondary reinforcing properties of nicotine

BACKGROUND

Clock genes have been demonstrated to play a role in behavioral responses to a variety of drugs of abuse, including cocaine, amphetamine, morphine, and ethanol. However, no studies to date have examined the role of Clock genes on nicotine-mediated behaviors. We examined the involvement of Clock, one of several Clock genes, on the effects of nicotine by examining mice with the ClockΔ19 mutation in behaviors commonly used to assess drug effects in rodents.

METHODS

We first measured the locomotor effects of nicotine in mutants and wild type mice in response to repeated nicotine injections (0.175 mg/kg, IP). To assess the secondary properties of nicotine, we measured the ability of nicotine (0.175 mg/kg, IP) to induce a conditioned place preference. Finally, we measured the primary reinforcing properties of nicotine at two doses (0.01 and 0.03 mg/kg/infusion, IV) using the self-administration paradigm.

RESULTS

Mutant mice demonstrated no difference in magnitude of the sensitized response to nicotine as compared to wild-type controls. In the conditioned place preference paradigm, mutant and wild-type mice demonstrated a similar preference for a nicotine-paired environment. And finally, mutant and wild-type mice demonstrated a similar acquisition of nicotine self-administration, as indicated by the number of responses on a nicotine-paired lever and the number of nicotine reinforcers achieved during sessions.

CONCLUSIONS

The ClockΔ19 mutation appears to have no effect on the reinforcing properties of nicotine, in contrast to its demonstrated role in cocaine reinforcement. Further studies are needed to determine the effect of other Clock genes on nicotine reinforcement.

Cognitive function during nicotine withdrawal: Implications for nicotine dependence treatment

Nicotine withdrawal is associated with deficits in neurocognitive function including sustained attention, working memory, and response inhibition. Several convergent lines of evidence suggest that these deficits may represent a core dependence phenotype and a target for treatment development efforts. A better understanding of the mechanisms underlying withdrawal-related cognitive deficits may lead to improve nicotine dependence treatment. We begin with an overview of the neurocognitive effects of withdrawal in rodent and human models, followed by discussion of the neurobehavioral mechanisms that are thought to underlie these effects. We then review individual differences in withdrawal-related neurocognitive effects including genetics, gender, and psychiatric comorbidity. We conclude with a discussion of the implications of this research for developing improved therapies, both pharmacotherapy and behavioral treatments, that target cognitive symptoms of nicotine withdrawal. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.

Memory-related effects of cholinergic receptor ligands in mice as measured by the elevated plus maze test

The purpose of our experiments was to examine the influence of cholinergic receptor ligands on memory-related behavior in mice using the elevated plus maze (EPM) test. The EPM test allows the exploration of different memory processes (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. Our findings reveal that for both the processes of acquisition and consolidation, treatment with nicotine (0.035 or 0.175 mg/kg, free base, sc) shortened TL on the second day of the experiments (TL2), thus improving memory processes. Treatment with scopolamine (0.3 or 1.0 mg/kg, ip) significantly increased TL2 values, thus impairing cognitive processes. Moreover, we found that treatment with nicotine, at the non-effective doses used during testing, prevented scopolamine-induced memory impairment by inducing a decrease in TL2 values. Next, we evaluated the influence of bupropion (10 or 20 mg/kg, ip), a drug currently used for smoking cessation in humans, on memory-related behavior induced by treatment with nicotine and scopolamine. An acute injection of bupropion (10 or 20 mg/kg) prior to injection with either nicotine (0.035 mg/kg) or scopolamine (1.0 mg/kg) significantly prevented nicotine-induced memory improvement or scopolamine-induced memory impairment. Bupropion treatment can diminish the rewarding (dependence-producing) effects of nicotine and also the cognitive effects that are related to addiction. Our studies further indicate the great involvement of the cholinergic system in memory processes and the potential for the development of more effective pharmacotherapies for memory impairment-like human disorders in which the cholinergic pathways have been implicated.

Assessments of the effects of nicotine and ketamine using tyrosine hydroxylase-green fluorescent protein transgenic zebrafish as biosensors

Transgenic zebrafish are a common vertebrate model system for the study of addictive behavior. In the present study, plasmid constructs containing green fluorescent protein (GFP) and the promoter of tyrosine hydroxylase (TH), a key synthetic enzyme for catecholamines, were produced. The TH-GFP constructs were microinjected into zebrafish embryonic cells. Three days post-fertilization, GFP began expressing in distinct catecholaminergic areas. The TH-GFP transgenic zebrafish were employed as live biosensors to test the effects of the commonly abused drugs nicotine and ketamine. First, locomotion assays were used to study the general excitatory effects of the drugs. Maximal locomotor activity was obtained after treatment with a high concentration of nicotine (10 μM), but with a much lower concentration of ketamine (0.1 μM). Second, TH protein levels in zebrafish brains were assessed by Western blot. TH protein levels were significantly increased, with maximal protein levels found after treatment with the same drug concentrations that gave maximal locomotor activity. Importantly, analysis of GFP in the zebrafish catecholaminergic areas revealed the same expression patterns as was obtained by Western blot. The present results indicate that increased locomotor activity can be correlated to TH protein expression, as indicated by Western blot and expression of TH-GFP. We have shown that TH-GFP expression is a reliable method to show the effects of drugs on TH expression that may be employed as a novel high-throughput live biosensor for screening drugs of abuse.

Anti-stress effects of cilnidipine and nimodipine in immobilization subjected mice

The present study was designed to investigate the ameliorative role of cilnidipine and nimodipine in immobilization stress-induced behavioral alterations and memory defects in the mice. Acute stress was induced by immobilizing the mice for 150 min and stress-induced behavioral changes were assessed using actophotometer, hole board, open field and social interaction tests. The learning and memory was evaluated using elevated plus maze tests and biochemically, the corticosterone levels were measured in the blood serum. Acute immobilization stress resulted in decrease in locomotor activity, frequency of head dips and rearings in hole board; line crossing and rearing in the open field; increase in avoidance in social behavior along with development of memory deficits assessed by an increased transfer latency time and elevation of the corticosterone levels. Administration of cilnidipine (10 mg/kg), an L and N-type dual calcium channel blocker, and nimodipine (10 mg/kg), an L-type calcium channel blocker, significantly attenuated the immobilized stress-induced behavioral changes and restored memory deficits along with normalization of the corticosterone levels. Cilnidipine and nimodipine produced comparable beneficial effects in restoring immobilization stress subjected mice. It may be concluded that cilnidipine and nimodipine mediated attenuation of corticosterone release by blockage of calcium channels (both L and N-type) on the HPA-axis is responsible for beneficial effects in restoration of behavioral alterations and memory deficits in immobilization-induced acute stress in mice.

Nicotinergic impact on focal and non-focal neuroplasticity induced by non-invasive brain stimulation in non-smoking humans

Nicotine improves cognitive performance and modulates neuroplasticity in brain networks. The neurophysiological mechanisms underlying nicotine-induced behavioral changes have been sparsely studied, especially in humans. Global cholinergic activation focuses on plasticity in humans. However, the specific contribution of nicotinic receptors to these effects is unclear. Henceforth, we explored the impact of nicotine on non-focal neuroplasticity induced by transcranial direct current stimulation (tDCS) and focal, synapse-specific plasticity induced by paired associative stimulation (PAS) in healthy non-smoking individuals. Forty-eight subjects participated in the study. Each subject received placebo and nicotine patches combined with one of the stimulation protocols to the primary motor cortex in different sessions. Transcranial magnetic stimulation (TMS)-elicited motor-evoked potential (MEP) amplitudes were recorded as a measure of corticospinal excitability until the evening of the second day following the stimulation. Nicotine abolished or reduced both PAS- and tDCS-induced inhibitory neuroplasticity. Non-focal facilitatory plasticity was also abolished, whereas focal facilitatory plasticity was slightly prolonged by nicotine. Thus, nicotinergic influence on facilitatory, but not inhibitory plasticity mimics that of global cholinergic enhancement. Therefore, activating nicotinic receptors has clearly discernable effects from global cholinergic activation. These nicotine-generated plasticity alterations might be important for the effects of the drug on cognitive function.