Effects of co-administration of bupropion and nicotinic agonists on the elevated plus-maze test in mice

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.

Evaluation of the Anxiolytic and Antidepressant Activities of the Aqueous Extract from Camellia euphlebia Merr. ex Sealy in Mice

Camellia euphlebia Merr. ex Sealy is a traditional Chinese medicine that has been widely used for improvement of human emotions in the Guangxi Province of southern China. However, there are no studies about the anxiolytic and antidepressant activities of Camellia euphlebia. This study evaluated the anxiolytic and antidepressant activities of the aqueous extract from Camellia euphlebia (CEE) in mice. We found that administration of 400 mg/kg CEE or 20 mg/kg fluoxetine for 7 days significantly reduced the immobility time in both TST and FST. Oral administration of 100 mg/kg extract or 4 mg/kg diazepam for 7 days significantly increased the percentage of time spent and the number of entries into the open arms of the EPMT. In addition, the time spent by mice in the illuminated side of the LDBT was increased. Furthermore, pretreatment with 400 mg/kg CEE for 7 days significantly elevated the level of 5-HT and DA in the whole brain of mice. These results provide support for the potential anxiolytic and antidepressant activity of Camellia euphlebia and contribute towards validation of the traditional use of Camellia euphlebia in the treatment of emotional disorders.

Age-contingent influence over accumbal neurotransmission and the locomotor stimulatory response to acute and repeated administration of nicotine in Wistar rats

Nicotine addiction is one of the leading contributors to the global burden of disease, and early onset smokers report a more severe addiction with lower chance of cessation than those with a late onset. Preclinical research supports an age-dependent component to the rewarding and reinforcing properties of nicotine, and the aim of this study was to define behavioral adaptations and changes in accumbal neurotransmission that arise over 15 days of intermittent nicotine treatment (0.36 mg/kg/day) in rats of three different ages (5 weeks, 10 weeks, 36 weeks old). Repeated treatment increased the locomotor stimulatory response to nicotine in all age groups, but significantly faster in the two younger groups. In addition, nicotine decreased rearing activity in a way that sustained even after repeated administration in aged rats but not in the younger age groups. Electrophysiological field potential recordings revealed a decline in input/output function in the nucleus accumbens (NAc) of animals intermittently treated with nicotine starting at 5 weeks of age, but not in older animals. In drug naïve rats, acute administration of nicotine modulated both accumbal dopamine output and excitatory transmission in a partially age-dependent manner. Fifteen days of intermittent nicotine treatment did not alter the acute effect displayed by nicotine on dopamine levels or evoked field potentials. The data presented here show that both acute and repeated nicotine administration modulates accumbal neurotransmission and behavior in an age-contingent manner and that these age-dependent differences could reflect important neurobiological underpinnings associated with the increased vulnerability for nicotine-addiction in adolescents.

Behavioral effects of different enriched environments in mice treated with the cholinergic agonist PNU-282987

Environmental enrichment is an experimental model in which rodents are housed in complex environments that favor lower levels of anxiety-like behavior. PNU-282987 (PNU) is a α7 nicotinic acetylcholine receptor agonist with beneficial effects on learning though its effects on anxiety are unclear. Our main aim was to carry out a study of its effects in NMRI (n=96) mice reared in different environments: environmental enrichment (EE), Marlau™ cages (MC) and standard environment (SE). After a 4-month period, mice received acute treatment of PNU (2.5, 5 and 10mg/kg) and were evaluated in the elevated plus-maze (EPM) and hole-board (HB). In the EPM, both EE and MC reared mice showed an increase in percentage of entries into open arms while those from EE group differed from SE in time spent on open arms. Mice treated with 2.5 and 10 mg/kg of PNU devoted less time to rearing into open arms. In the HB task, MC mice displayed higher exploratory activity reflected in more head-dips (HD) during the first minute than EE and SE, whereas EE displayed low exploration levels reflected in total HD (5 min). Further research is needed in order to clarify the behavioral effects of this nicotinic agonist in interaction with different environmental conditions. This article is part of a Special Issue entitled: insert SI title.

Bupropion induced changes in exploratory and anxiety-like behaviour in NMRI male mice depends on the age

The aim of this study was to assess the effects of the antidepressant bupropion on anxiety and novelty-seeking in adolescent mice of different ages and adults. Behavioural differences between early adolescent, late adolescent and adult NMRI mice were measured both in the elevated plus-maze and the hole-board tasks following acute administration of bupropion (5, 10, 15, 20mg/kg) or saline. In the plus maze test, early and late adolescent mice treated with bupropion (10, 15mg/kg, respectively) had lower percentages of entries in the open-arms compared to their vehicle controls. Adult mice treated with bupropion did not differ from their vehicle controls. These results suggest that the effect of this drug on anxiety-like behaviour in mice depends on the age, showing adolescents an anxiogenic-like profile. In the hole-board, adolescents showed more elevated levels of novelty-seeking than adults, exhibiting shorter latency to the first head-dip (HD) and a higher number of HD's. Bupropion increases the latency to the first HD and decreases the number of HD's in all age-groups, indicating a decline in exploratory tendency. Findings reveal that the age can modulate the behaviour displayed by mice in both animal models, and that adolescents are more sensitive to bupropion's anxiogenic effects.

Antidepressant activity of Litsea glaucescens essential oil: identification of β-pinene and linalool as active principles

ETHNOPHARMACOLOGICAL RELEVANCE

Litsea glaucescens (Lauraceae) has been used in Mexican Traditional Medicine to relieve illness related to central nervous system, such as epilepsy, fright and sadness. In this study, L. glaucescens essential oil properties on central nervous system were evaluated in mice using different behavioral tests.

MATERIALS AND METHODS

The essential oil was obtained by hydrodistillation and analyzed by GC/MS. Identification of major compounds was also carried out by comparison with authentic samples. The psychopharmacological profile of L. glaucescens essential oil, and some its major compounds, were evaluated in mice using several experimental models: forced swimming test (FST: Antidepressant-like activity), open field test (OFT: Spontaneous locomotor activity), elevated plus-maze (EPM: Anxiolytic-like activity), exploratory cylinder (ECT: Sedative-like activity), rotarod (motor coordination) and traction performance (myo-relaxant effect) the essential oil and active principles was administered intraperitoneally.

RESULTS

The essential oil showed antidepressant-like activity at doses of 100 and 300 mg/Kg. The monoterpenes β-pinene and linalool were identified as the two main active principles of the essential oil, and showed antidepressant-like and sedative-like activity. Eucalyptol, limonene and α-pinene they did not show antidepressant-like activity, and were not further tested.

CONCLUSIONS

L. glaucescens essential oil showed antidepressant activity, β-pinene and linalool were identified as its active principles. These results support the use of L. glaucescens in Mexican Traditional Medicine for the treatment of sadness.

Neuronal nicotinic receptor antagonist reduces anxiety-like behavior in mice

Brain cholinergic neurotransmission has been implicated in the modulation of anxiety in humans and evidence suggests that drugs targeting neuronal nicotinic acetylcholine receptor (nAChR) could have potential for the treatment of anxiety. The objective of present study was to examine anxiolytic effects of lobeline (0.04 or 0.1 mg/kg), a nAChR antagonist, in C57BL/6J mice using elevated plus-maze (EPM) and marble-burying test. Lobeline (0.04 mg/kg) significantly increased open arm time on EPM and reduced number of marbles buried. Similarly, mecamylamine (0.3 mg/kg) produced anxiolytic effects, while peripherally acting hexamethonium (0.3 mg/kg) failed to produce any response. These results provide evidence that lobeline has anxiolytic potential and nAChR antagonists may represent a new class of anxiolytics in humans.

Behavioral effects of PNU-282987, an alpha7 nicotinic receptor agonist, in mice

The cholinergic system is closely related to learning and memory processes, and its neurodegeneration seems to be involved in neurodegenerative and neuropsychiatric cognitive disorders in the elderly. Alpha7 nicotinic acetylcholine receptors (nAChRs) have recently been shown to mediate neuroprotection and enhance cognitive performance in a variety of tasks, suggesting that there may be a new target for the pharmacotherapy of cognitive deficiencies. In this study, we investigated the behavioral effects of the acute and sub-chronic administration of 0, 1, 3, and 5 mg/kg of PNU-282987 (PNU) on motor activity, anxiety and learning in open-field and Morris water maze tasks in mice. Our results showed that the highest dose of PNU (5 mg/kg) diminished motor activity in the open-field following 5 and 12 days of administration (acute and sub-chronic, respectively). No effects on the acquisition of the Morris water maze were observed. However, only 1 mg/kg of PNU administered just before training trials over a period of 5 days showed beneficial effects on the retention of the water maze when evaluated 4 h after water maze acquisition. Further studies are needed to clarify the effects on the cognitive performance and potential neuroprotection of these agents in an elderly population with slight or severe deficiency in learning and memory processes, and/or in animal models vulnerable to neurodegenerative disorders.

Effects of co-administration of bupropion and nicotine or d-amphetamine on the elevated plus maze test in mice

Objectives

A variety of abused drugs, including psychostimulants, can modulate the expression of anxiety. Although the effect of nicotine and d-amphetamine on anxiety-related behaviour in animal models has been investigated, the mechanisms underlying the anxiogenic or anxiolytic actions of these drugs have not been clarified. Bupropion is an antidepressant drug which may alleviate some symptoms of nicotine withdrawal, although its effects on anxiety are not clear. We have investigated the effect of nicotine and d-amphetamine on anxiety in the elevated plus maze test in mice.

Methods

We examined the influence of acute administration of nicotine (0.1 mg/kg, s.c.) and d-amphetamine (2 mg/kg, i.p.) on anxiety level. We then evaluated the anxiety-related response after subchronic injection of both psychostimulants, including crossover effects. For this purpose, nicotine (0.1 mg/kg, s.c.) was administered daily for six days, and on the seventh day mice were challenged with nicotine (0.1 mg/kg, s.c.) or d-amphetamine (2 mg/kg, i.p.). A distinct group of mice was pretreated with d-amphetamine (2 mg/kg, i.p., 8 days), and subjected to d-amphetamine (2 mg/kg, i.p.) or nicotine (0.1 mg/kg, s.c.) challenge on the ninth day. Moreover, we investigated acute and subchronic effects of co-administration of bupropion (5, 10 and 20 mg/kg; i.p.) and nicotine or d-amphetamine.

Key findings

We observed that acute anxiogenic effects of nicotine and d-amphetamine as well as the development of tolerance and cross-tolerance to their effects were blunted by a pretreatment with a nonactive dose of bupropion (5 mg/kg, i.p.).

Conclusions

These results demonstrated that similar neural mechanisms were involved in the regulation of nicotine and d-amphetamine anxiety-like behaviour in mice. The results have provided new findings to support the use of bupropion in the treatment of nicotine and/or amphetamine addiction.

Behavioural and pharmacological mechanisms of bupropion's anti-smoking effects: recent preclinical and clinical insights

Ongoing studies continue to explore the behavioural and pharmacological effects of bupropion in smoking cessation studies and animal models of nicotine dependence. In the present review, the components of nicotine dependence that form the most likely targets of bupropion are identified within the context of an expanding preclinical and clinical literature regarding the anti-addictive properties of bupropion. Second, preclinical and clinical data that implicate specific pharmacological modes of action of bupropion in mediating the anti-smoking effects of the compound are discussed. Third, it is suggested that the unique mixed pharmacological profile of bupropion provides (1) attenuation of the multiple negative consequences of withdrawal via blockade of dopamine and noradrenaline reuptake; (2) replacement of the reward-facilitating and subjective effects of nicotine via blockade of dopaminergic reuptake; (3) attenuation of the rewarding effects of acute nicotine by nicotinic acetylcholine receptor blockade. The importance of species differences in bupropion metabolism in the interpretation of preclinical studies is highlighted. Finally, future studies are suggested to address identified gaps in the knowledge: most importantly, to provide stronger evidence for the role of noradrenaline reuptake inhibition in bupropion-induced attenuation of nicotine withdrawal. Future studies aimed at providing more evidence for the three-fold nature of the anti-smoking effects of bupropion are also suggested, along with the possibility of utilizing adjunct therapies to improve smoking cessation rates.

Effects of bupropion, alone or coadministered with nicotine, on social behavior in mice

Bupropion, administered alone or combined with nicotine, is presently used to treat nicotine dependence. Despite experimental evidence of the complex behavioral actions of this drug, there have been little data reported about its effects on social behavior. Our main aim was to investigate the effects of acute administration of bupropion, alone or plus nicotine, on social interaction in mice. OF1 group-housed male mice were confronted in a neutral cage with an anosmic opponent during a 10 minutes encounter. Time allocated to body care and digging was reduced by administration of bupropion (40 mg/kg) both when administered alone and with nicotine (1 and 0.5 mg/kg). The lowest dose of bupropion (10 mg/kg) also reduced digging when combined with 1 mg/kg of nicotine. Time spent on non-social exploration and exploration from a distance was significantly higher in mice treated with bupropion (40 mg/kg) alone or combined with nicotine (1 and 0.5 mg/kg). The lowest dose of bupropion (10 mg/kg) increased non-social exploration when combined with 0.5 mg/kg of nicotine and exploration from a distance when combined with 1 mg/kg of nicotine. Ethopharmacological assessment of the behavior of groups of mice treated with different combinations of the two drugs indicates that nicotine can potentiate some of the behavioral effects of low doses of bupropion. Results also indicate that bupropion, either alone or combined with nicotine, has no significant effects on social investigation, suggesting that this drug does not induce a clear anxiolytic profile in OF1 mice.

Differential sensitivity to the effects of nicotine and bupropion in adolescent and adult male OF1 mice during social interaction tests

Few studies have compared the action of both nicotine (NIC) and bupropion (BUP), an antidepressant used to treat NIC dependence, on social and aggressive behavior at different ages. This study aims to determine whether these drugs produce differential effects in adolescent (postnatal day: 36-37) and adult (postnatal day: 65-66) mice that have been housed individually for 2 weeks in order to induce aggressive behavior. Mice received BUP (40, 20, or 10 mg/kg), NIC (1, 0.5, and 0.25 mg/kg as base), or vehicle earlier to a social interaction test. BUP (40 mg/kg) decreased social investigation and increased nonsocial exploration in both adolescent and adult mice. The same effects were also observed in adult mice administered with a lower dose of the same drug (20 mg/kg). In adolescents, NIC (1 mg/kg) decreased social investigation, but this effect did not reach statistical significance in adults. In conclusion, a differential sensitivity to the effects of NIC or BUP emerged in some of the behavioral categories when the two age groups were compared.

Cytisine, a partial agonist of high-affinity nicotinic acetylcholine receptors, has antidepressant-like properties in male C57BL/6J mice

The nicotine in tobacco is thought to modulate neuronal systems regulating mood. Moreover, it appears possible that blockade rather than activation of beta2-containing (beta2*) nicotinic acetylcholine receptors (nAChRs) may lead to antidepressant-like effects. We used cytisine, a partial agonist of alpha4/beta2*nAChRs and a full agonist at alpha3/beta4*nAChRs, in several tests of antidepressant efficacy. Further, we used c-fos expression to identify potential neurobiological correlates of the antidepressant-like effects of cytisine. Cytisine had antidepressant-like effects in several animal models of antidepressant efficacy. In addition, immunohistochemical analyses indicated that cytisine could reduce c-fos immunoreactivity in the basolateral amygdala by approximately 50%. These data show that cytisine acts like classical antidepressants in rodent models of antidepressant efficacy. In addition, cytisine's ability to block alpha4/beta2*nAChRs may be responsible for its antidepressant-like properties, and these may be mediated through a reduction of neuronal activity in the basolateral amygdala. These studies also suggest that both antagonists and partial agonists of alpha4/beta2*nAChRs would be interesting targets for the development of novel antidepressant drugs.

Review of the pharmacology and clinical profile of bupropion, an antidepressant and tobacco use cessation agent

Bupropion hydrochloride ((+/-)-2-tert-butylamino)-3'-chloropropiophenone x HCl) is a nonselective inhibitor of the dopamine transporter (DAT) and the norepinephrine transporter (NET) and is also an antagonist at neuronal nicotinic acetylcholine receptors (nAChRs). In animal models used commonly to screen for antidepressant activity, bupropion shows a positive response. Also using animal models, bupropion has been shown to attenuate nicotine-induced unconditioned behaviors, to share or enhance discriminative stimulus properties of nicotine and to have a complex effect on nicotine self-administration, i.e., low doses augmenting nicotine self-administration and high doses attenuating self-administration. Current studies show that bupropion facilitates the acquisition of nicotine conditioned place preference in rats, further suggesting that bupropion enhances the rewarding properties of nicotine. Bupropion has been shown to attenuate the expression of nicotine withdrawal symptoms in both animal models and human subjects. With respect to relapse, current studies show that bupropion attenuates nicotine-induced reinstatement in rats, but large individual differences are apparent. Clinically, bupropion is used as a treatment for two indications, as an antidepressant, the indication for which it was developed, and as a tobacco use cessation agent. In clinical trials, bupropion is being tested as a candidate treatment for psychostimulant drug abuse, attention-deficit hyperactivity disorder (ADHD) and obesity. Bupropion is available in three bioequivalent oral formulations, immediate release (IR), sustained release (SR), and extended release (XL). Extensive hepatic metabolism of bupropion produces three pharmacologically active metabolites, which may contribute to its clinical profile.