Increased anxiety-like behavior in adult rats exposed to nicotine as adolescents

OBJECTIVE: Twenty percent of adolescents between 12 and 18 years old are regular smokers. Recently developed animal models demonstrate that adolescent nicotine exposure produces behavioral and electrophysiological changes, which persist into adulthood. The purpose of this study was to further define the behavioral effects of nicotine exposure during adolescence. METHODS: Male 31-36-day-old adolescent rats were administered 5.0 mg/kg/day nicotine using transdermal Nicoderm CQ patches (SmithKline Beecham). During nicotine exposure, motor activity was assessed. Behavior in both standard open field and modified open field was examined 2-3 weeks after exposure ended. RESULTS: Nicotine exposure significantly enhanced motor activity in nicotine-exposed rats compared with controls, demonstrating the acute stimulatory effects of transdermal nicotine. Two to three weeks after nicotine exposure ended, significantly lower levels of exploratory activity were observed relative to controls in the standard open field. Rats exposed to nicotine during adolescence also retreated to the perimeter of the open field more quickly than control rats. In a modified open field, nicotine exposure reduced approaches to food, contact with food and food intake. CONCLUSIONS: Taken together, these data suggest that adolescent nicotine exposure may induce an anxiogenic profile, which persists beyond acute nicotine withdrawal. Given the hypothesized role of stress and anxiety in the maintenance of smoking, it could be speculated that anxiety associated with smoking abstinence may play an important role in continued adolescent tobacco use.     

Long-term changes in fear conditioning and anxiety-like behavior following nicotine exposure in adult versus adolescent rats

Adolescent nicotine exposure is associated with long-term use, and it has been suggested that this vulnerability to addiction may relate to lasting anxiogenic effects of the drug. However, few studies have addressed long-term effects of adolescent nicotine, and fewer yet have compared adolescent to adult exposure. Male and female Long-Evans rats continuously received nicotine bitartrate or sodium tartrate via osmotic mini-pumps over 15 days either during adolescence (p28-42) or adulthood (p85-99). Initial nicotine dose (free base) was either low (1 mg/kg/day) or high (2 mg/kg/day). Open field behavior and fear conditioning were assessed in adulthood, 1 month post-dosing. Animals pretreated with nicotine during adolescence showed less center time in a novel open field than sham controls. Conversely, the two nicotine doses differentially affected fear conditioning. Animals pretreated with low nicotine during adolescence demonstrated superior acquisition of the task compared to sham control animals; however, unlike either high nicotine-pretreated or sham control animals, they failed to extinguish the learned behavior. In contrast, animals pretreated during adulthood did not behave significantly different from sham controls on either task. Overall, nicotine-pretreatment during adolescence induced effects on behaviors related to fear and anxiety in adulthood, while comparable pretreatment during adulthood failed to produce significant residual effects.     

Influence of fluoxetine and paroxetine on anxiety-like behavior in young and adult prenatally stressed male rats

We present the results of a comparative analysis of the effects of the chronic administration of the selective serotonin reuptake inhibitors fluoxetine (5.0 mg/kg, p.o.) and paroxetine (5.0 mg/kg, p.o.) for 14 days of the postnatal period on anxiety-like behavior in the prenatally stressed male rats as studied during pubertal period (1.5 month) and in the adult age (3 month). The chronic administration of paroxetine in male rats did not change the anxiety-like behavior in male rates of any age. On the contrary, the administration of fluoxetine modulated the anxiety-like behavior of prenatally stressed rats depending on the age: the anxiolytic effect was observed in young males, while the anxiogenic effect was observed in adult male rats.     

Effect of intra-amygdala injection of nicotine and GABA receptor agents on anxiety-like behaviour in rats

There is evidence that both cholinergic and GABAergic systems are involved in the neurobiology of anxiety. In the present study, we investigated the effects and interaction of nicotinic and GABAergic systems in the central amygdala of rats, using the elevated plus maze test of anxiety. Bilateral administration of nicotine (1 and 2 microg/rat; 1 microl/rat; 0.5 microl/rat in each side) into the central amygdala (intra-CeA) induced an anxiogenic-like effect, shown by specific decreases in the percentage of open-arm time (%OAT) and percentage of open arm entries (%OAE). Intra-CeA injection of mecamylamine, a selective nicotine acetylcholine receptor antagonist (20, 30 and 50 ng/rat; 1 microl/rat; 0.5 microl/rat in each side) produced significant anxiolytic-like behaviour. The intra-CeA injection of the GABAA receptor agonist muscimol (0.25, 0.5 and 0.75 microg/rat; 1 microl/rat; 0.5 microl/rat in each side) decreased %OAT and %OAE, indicating anxiogenic-like behaviour. However, intra-CeA administration of the GABAA receptor antagonist bicuculline (0.25, 0.5 and 1 microg/rat; 1 microl/rat; 0.5 microl/rat in each side) produced significant anxiolytic-like behaviour. Nicotine in a subeffective dose (0.25 microg/rat) when co-administered with muscimol did not significantly increase the anxiety behaviour. An effective dose of nicotine (2 microg/rat) in combination with bicuculline (0.25, 0.5 and 1 microg/rat) had no interaction on %OAT, %OAE and locomotor activity. It can be concluded that in the central amygdala, the GABAergic system is not involved in the anxiogenic response to nicotine.     

Effects of nano and conventional Zinc Oxide on anxiety-like behavior in male rats

Objectives:

Current drug therapies for psychological disorders, such as anxiety, are not as effective as expected, and it has been shown that zinc supplements, such as zinc oxide (ZnO), can influence anxiety. ZnO nanoparticles (ZnO NPs) are among the most used nanomaterials produced and applied in many products.

Materials and Methods:

This study investigated the effects of ZnO NPs in comparison with conventional ZnO (cZnO) on anxiety-like behaviors. Adult male Wistar rats were divided into groups: Control (receiving saline 0.9%), ZnO NPs (5, 10, 20 mg/kg), and cZnO (5, 10, 20 mg/kg). All drugs were dispersed in saline 0.9%, and 30 minutes after intraperitoneal (i.p.) injection of drugs, elevated plus maze apparatus was used to evaluate anxiety.

Results:

ZnO NPs (5 mg/kg) and cZnO (10 and 20 mg/kg) significantly increased the percentage of time spent in open arm (open arm time % OAT) compared with the control group (P < 0.05). This indicates the anxiolytic effect of such components; in addition, ZnO NPs (20 mg/kg) reduced locomotor activity (P < 0.05). Serum zinc concentration increased by both anxiolytic dose of components (from 1.75 ± 1.07 (mg/l) in control group to 5.31 ± 0.53 (mg/l) in ZnO NPs (5 mg/kg) and 10.38 ± 0.90 (mg/l) in cZnO (10 mg/kg) groups). Also, all doses increased serum pH (from 7.3 ± 0.05 in control group to 8.1 ± 0.05 in ZnO NPs (5 mg/kg) and 8.05 ± 0.01 in cZnO (10 mg/kg) groups and kept them constant after 24 hours.

Conclusion:

Results indicate that the anxiolytic effect of ZnO NPs is much higher than its conventional form, but the introduction of ZnO NPs, as a new drug for treatment of anxiety disorder, needs further investigations.KEY WORDS: Anxiety, Nano ZnO, plus maze, rat     

Late emerging effects of prenatal and early postnatal nicotine exposure on the cholinergic system and anxiety-like behavior

Animal models of prenatal nicotine exposure clearly indicate that nicotine is a neuroteratogen. Some of the persisting effects of prenatal nicotine exposure include low birth weight, behavioral changes and deficits in cognitive function, although few studies have looked for neurobehavioral and neurochemical effects that might persist throughout the lifespan. Pregnant rats were given continuous infusions of nicotine (0.96 mg/kg/day or 2.0 mg/kg/day, freebase) continuing through the third trimester equivalent, a period of rapid brain development. Because the third trimester equivalent occurs postnatally in the rat (roughly the first week of life) nicotine administration to neonate pups continued via maternal milk until postnatal day (P) 10. Exposure to nicotine during pre- and early postnatal development had an anxiogenic effect on adult rats (P75) in the elevated plus maze (EPM), and blocked extinction learning in a fear conditioning paradigm, suggesting that pre- and postnatal nicotine exposure affect anxiety-like behavior and cognitive function well into adulthood. In contrast, nicotine exposure had no effect on anxiety-like behaviors in the EPM in adolescent animals (P30). Analysis of mRNA for the α4, α7, and β2 subunits of nicotinic acetylcholine receptors revealed lower expression of these subunits in the adult hippocampus and medial prefrontal cortex following pre- and postnatal nicotine exposure, suggesting that nicotine altered the developmental trajectory of the brain. These long-term behavioral and neurochemical changes strengthen the case for discouraging cigarette smoking during pregnancy and clearly indicate that the use of the patch as a smoking cessation aid during pregnancy is not a safe alternative.     

Acute effects of nicotine on restraint stress-induced anxiety-like behavior, c-Fos expression, and corticosterone release in mice

Clinical evidence suggests that nicotine reduces anxiety in stressful situations. In the present study, we investigated the effect of nicotine on restraint-enhanced anxiety-like behavior, c-Fos expression, an index of neuronal activation in the brain, and plasma corticosterone. Two-hour restraint stress-enhanced anxiety-like behavior in the elevated plus-maze (EPM) and nicotine hydrogen tartrate (0.25 mg/kg, i.p.) attenuated the stress-induced changes. Pretreatment with the centrally acting nicotinic antagonist, mecamylamine (2 mg/kg), blocked nicotine's effects. In addition, restraint led to significant increases of c-Fos expression in several brain regions related to stress or anxiety including paraventricular hypothalamic nucleus (PVN), lateral hypothalamic area (LH), central amygdaloid nucleus (CeA), medial amygdaloid nucleus (MeA) and cingulate and retrosplenial cortices (Cg/RS), paraventricular thalamic nucleus (PVT), and basolateral amygdaloid nucleus (BLA). Nicotine attenuated the restraint-induced expression of c-Fos in the PVN, LH, CeA, MeA, and Cg/RS, while leaving the BLA and PVT unaffected. In contrast, nicotine did not reverse the increased levels of plasma corticosterone induced by restraint. These findings suggest that nicotine may modify the stress-induced behavioral changes via regulating the neuronal activation in selected brain regions rather than affecting hypothalamo-pituitary-adrenocortical axis hormone responses.     

Cerebral acetylcholine levels and long-term spatial cognitive impairment following middle cerebral artery occlusion in rats.

The behavioral and neurochemical changes in the chronic phase of permanent occlusion of the right middle cerebral artery (MCA) in rats were investigated. Nineteen MCA-occluded rats failed to solve the 8-arm radial maze task (cognitively impaired rats), while 11 MCA-occluded rats could complete it (cognitively unimpaired rats). When a delay of 60 min was imposed in the task, however, 5 cognitively unimpaired rats failed to complete the task. The rats that underwent behavioral testing were studied for any changes in ACh levels in various brain regions using HPLC with electrochemical detection. The ACh levels in the infarcted areas decreased considerably in all MCA-occluded rats, but no region of the infarcted areas correlated with the spatial cognitive deficit. The ACh levels tended to decrease in the frontal cortex of the cognitively impaired rats and greatly increased in both ipsilateral and contralateral parietal cortex of the cognitively unimpaired rats. A significant correlation was observed between the ACh levels and spatial cognitive deficit in the contralateral frontal cortex, and ipsilateral and contralateral parietal cortex. These results suggest that the cholinergic function of the frontal and parietal cortices might play a role in acquiring spatial cognition in MCA-occluded rats.     

Chronic transdermal nicotine patch treatment effects on cognitive performance in age-associated memory impairment

Objectives Chronic transdermal nicotine has been found to improve attentional performance in patients with Alzheimers disease (AD), but little is known about chronic nicotine effects in age-associated memory impairment (AAMI), a milder form of cognitive dysfunction. The current study was performed to determine the clinical and neuropsychological effects of chronic transdermal nicotine in AAMI subjects over a 4-week period.Design The double-blind, placebo-controlled, cross-over study consisted of two 4-week periods separated by a 2-week washout period.Setting An outpatient setting was used.Participants The subjects (n=11) met criteria for AAMI.Interventions The subjects were given nicotine patches (Nicotrol) to wear for 16 h a day at the following doses: 5 mg/day during week 1, 10 mg/day during week 2 and week 3 and 5 mg/day during week 4.Measurements The effects of nicotine treatment were determined with the clinical global impressions questionnaire, Conners Continuous Performance test, and the automated neuropsychologic assessment metrics (ANAM) computerized neuropsychology battery.Results Nicotine significantly improved the clinical global impression score as assessed by participants, as well as objective tests of attentional function on the Connors Continuous Performance Test and decision reaction time on the neuropsychology test battery. Nicotine did not improve performance on other tests measuring motor and memory function.Conclusion Chronic transdermal nicotine treatment in AAMI subjects caused a sustained improvement in clinical symptoms and objective computerized tests of attention. These results support the further investigation of nicotinic treatment as a promising therapy for AAMI.     

Minocycline reverses diabetes-associated cognitive impairment in rats

BackgroundMinocycline a tetracycline antibiotic is known for anti-inflammatory and neuroprotective actions. Here we determine the therapeutic potential of minocycline against type 2 diabetes associated cognitive decline in rats.MethodsHigh fat diet (HFD) and low dose streptozotocin (STZ; 25 mg/kg) were used to induce diabetes in Sprague-Dawley rats. Fasting blood glucose and haemoglobin (Hb) A1c were measured in these animals. Cognitive parameters were measured using passive avoidance and elevated plus maze test. Hippocampal Acetylcholine esterase (AchE), reduced glutathione (GSH), cytokines, chemokine levels were measured and histopathological evaluations were conducted. The diabetic animals were then given minocycline (50 mg/kg; 15 days) and the above parameters were reassessed. MTT and Lactate dehydrogenase (LDH) assays were conducted on neuronal cells in the presence of glucose with or without minocycline treatment.ResultsWe induced diabetes using HFD and STZ in these animals. Animals showed high fasting blood glucose levels (>245 mg/dl) and HbA1c compared to control animals. Diabetes significantly lowered step down latency and increased transfer latency. Diabetic animals showed significantly higher AchE, Tumor necrosis factor (TNF)-α, Interleukin (IL)-1β and Monocyte chemoattractant protein (MCP)-1 and lower GSH levels and reduced both CA1 and CA3 neuronal density compared to controls. Minocycline treatment partially reversed the above neurobehavioral and biochemical changes and improved hippocampal neuronal density in diabetic animals. Cell line studies showed glucosemediated neuronal death, which was considerably reversed upon minocycline treatment.ConclusionsMinocycline, primarily by its anti-inflammatory and antioxidant actions prevented hippocampal neuronal loss thus partially reversing the diabetes-associated cognitive decline in rats.     

L-NAME prevents anxiety-like and depression-like behavior in rats exposed to restraint stress

Stressful life events contribute to the development of many neuropsychiatric disorders including depression and anxiety. Animal studies based on the relationship of stress and depression or anxiety are scarce and controversial. Moreover, neither the neurobiological basis of anxiety and depression nor the mechanisms responsible for neurochemical regulation by stressful stimuli are well understood. This study was designed to investigate the possible contribution of both acute (2 h) and chronic (2 h X 15 d) restraint stress in the generation of anxiety and depression, and also to find out whether nitric oxide (NO) has a modulatory role in these behavioral reactions. Elevated plus-maze and forced swimming test (FST) were chosen for assessment of anxiety and depression, respectively, and N(G)-nitro L-arginine methyl ester (L-NAME, 10 mg/kg), a NO synthase (NOS) inhibitor, and L-arginine (50 mg/kg), a NO precursor, were used to evaluate the role of nitrergic system in restraint exposed rats. The results showed that acute and chronic stress caused depression-like and anxiety-like behaviors in rats and the acute inhibition of NOS by L-NAME prevented these acute and chronic stress-induced anxiogenesis and depression. These data lead to the conclusion that stress and NO seem to be involved in the generation of anxiety and depression.     

Chronic unpredictable stress induces a cognitive deficit and anxiety-like behavior in rats that is prevented by chronic antidepressant drug treatment.

Chronic stress is a risk factor for the development of many psychopathological conditions in humans, including major depression and anxiety disorders. There is a high degree of comorbidity of depression and anxiety. Moreover, cognitive impairments associated with frontal lobe dysfunction, including deficits in cognitive set-shifting and behavioral flexibility, are increasingly recognized as major components of depression, anxiety disorders, and other stress-related psychiatric illnesses. To begin to understand the neurobiological mechanisms underlying the cognitive and emotional consequences of chronic stress, it is necessary to employ an animal model that exhibits similar effects. In the present study, a rat model of chronic unpredictable stress (CUS) consistently induced a cognitive impairment in extradimensional set shifting capability in an attentional set shifting test, suggesting an alteration in function of the medial prefrontal cortex. CUS also increased anxiety-like behavior on the elevated plus-maze. Further, chronic treatment both with the selective norepinephrine reuptake blocker, desipramine (7.5 mg/kg/day), and the selective serotonin reuptake blocker, escitalopram (10 mg/kg/day), beginning 1 week before CUS treatment and continuing through the behavioral testing period, prevented the CUS-induced deficit in extradimensional set-shifting. Chronic desipramine treatment also prevented the CUS-induced increase in anxiety-like behavioral reactivity on the plus-maze, but escitalopram was less effective on this measure. Thus, CUS induced both cognitive and emotional disturbances that are similar to components of major depression and anxiety disorders. These effects were prevented by chronic treatment with antidepressant drugs, consistent also with clinical evidence that relapse of depressive episodes can be prevented by antidepressant drug treatment.     

Inhibition of fatty acid amide hydrolase modulates anxiety-like behavior in PCP-treated rats

Sub-chronic administration of PCP produces a social interaction deficit that is reversed by URB597, an inhibitor of the catabolic enzyme of the endocannabinoid anandamide. Since increased anxiety may contribute to social withdrawal and URB597 has been shown to have an anxiolytic action, we studied whether this drug affected saline- and PCP-treated rats' performance in the Elevated-Plus-Maze task, which has been used to assess anxiety-like effects. Sub-chronic PCP produced a CB₁-dependent decrease in anxiety-like behavior that was reversed by URB597 in a CB₁-independent fashion, as it was not blocked by the CB₁ antagonist AM251. These findings suggest that PCP-treated rats have altered endocannabinoid transmission and that anxiety does not contribute to the PCP-induced social withdrawal.     

Adriamycin-related anxiety-like behavior, brain oxidative stress and myelotoxicity in male Wistar rats

Chemotherapeutic regimens have been indicated to negatively impact the quality of life for patients. Adriamycin (ADR) is an effective chemotherapeutic agent widely employed for the treatment of human's malignancies; however, it may cause serious side effects. The present study was aimed at investigating the effects of acute administration of ADR on cognitive alterations, brain oxidative status and immune dysregulation in male Wistar rats. Treated animals received a single intraperitoneal injection of ADR (7 mg/kg). Control ones received physiological saline only. Behavioral effects were tested in the elevated plus-maze and the open field which showed that drug-treated rats displayed anxious behavior and deteriorations in the locomotive and exploratory activities over the 72 h following ADR injection as compared to controls. Assessment of brain antioxidant capacity in ADR-injected animals revealed an increase in glutathione-S-transferase activities and malondialdehyde levels while a decrease in glutathione concentrations when compared with the vehicle-treated group. Our results indicated that ADR administration decreased total leukocyte, lymphocyte and granulocyte counts, while enhanced monocyte levels. Moreover, white blood cells (WBC) relative counts in ADR-treated rats showed a significant increase in monocytes and granulocytes and a decrease in lymphocytes as compared to controls. This study suggests that ADR-related cognitive impairments are associated with brain oxidative stress and myelosuppression.     

白藜芦醇对糖尿病大鼠认知功能损害的改善作用

目的观察白藜芦醇对糖尿病大鼠认知功能的影响并探讨其作用机制。方法 60只SD大鼠随机分为3组,即对照组、模型组和治疗组,每组20只。模型组和治疗组大鼠接受链脲佐菌素腹腔注射建立糖尿病模型。治疗组大鼠于造模后给予白藜芦醇治疗。利用Morris水迷宫检测大鼠空间认知能力;ELISA试剂盒测定大鼠海马炎症因子指标TNF-α和IL-6的表达,利用Western blot法检测大鼠海马部位凋亡相关蛋白(Bax、Bcl-2及Caspase-3)的表达。结果与对照组大鼠相比,模型组大鼠认知功能下降,海马TNF-α和IL-6的含量明显升高(P<0.05);与模型组大鼠相比,治疗组大鼠认知能力提高,海马TNF-α和IL-6的含量明显降低(P<0.05)。与对照组大鼠相比,模型组大鼠海马Bax和Caspase-3的含量明显升高(P<0.05),Bcl-2的表达明显降低(P<0.05);与模型组大鼠相比,治疗组大鼠海马Bax和Caspase-3的含量明显降低(P<0.05),Bcl-2的表达升高显著(P<0.05)。结论白藜芦醇治疗可改善糖尿病大鼠空间认知功能的损害,其发挥神经保护作用的机制可能与抑制凋亡途径和抗炎作用密切相关。     

Effects of the combination of metyrapone and oxazepam on intravenous nicotine self-administration in rats

Rationale

Despite increased education regarding its dangers, cigarette smoking remains a significant public health concern due to serious associated health consequences such as cancer and respiratory and cardiovascular diseases. Most smokers fail in their attempts to quit smoking, and current pharmacological interventions have relatively low levels of efficacy and are associated with significant adverse events. We have previously reported that combinations of metyrapone and oxazepam, administered at doses that were ineffective when delivered singly, resulted in dose-related decreases in cocaine self-administration in rats while not affecting food-maintained responding during the same sessions.

Objectives

The current study was designed to test the effects of the administration of a metyrapone:oxazepam combination on nicotine self-administration in rats.

Methods

Several dose combinations of metyrapone (12.5, 25 or 50 mg/kg) and oxazepam (5 or 10 mg/kg) were tested in rats trained to intravenously (IV) self-administer nicotine (0.03 mg/kg/infusion) during 1-h self-administration sessions using both fixed-ratio and progressive-ratio (PR) schedules of reinforcement.

Results

The administration of low doses of metyrapone and oxazepam in combination significantly decreased IV nicotine self-administration in rats. At the lowest doses of 12.5 mg/kg of metyrapone and 5 mg/kg of oxazepam, the drugs alone did not decrease IV nicotine self-administration, but the combination was effective. Varenicline was also tested using the fixed-ratio schedule, and reductions in nicotine intake were similar to those seen with the moderate dose of the combination.

Conclusions

The results of this study suggest a potential utility of the combination of metyrapone and oxazepam for smoking cessation in humans.