Acupuncture reduces nicotine-induced norepinephrine release in the hypothalamus via the solitary NMDA receptor/NOS pathway.

Noradrenergic projections from the nucleus tractus solitarius (NTS) to the hypothalamic paraventricular nucleus (PVN) are involved in nicotine (Nic) dependence. Nic induces hypothalamic norepinephrine (NE) release through N-methyl-d-aspartate receptors (NMDARs) and nitric oxide in the NTS. However, acupuncture attenuates Nic withdrawal-induced anxiety. Therefore, this study investigated the effects of acupuncture on Nic-induced hypothalamic NE release. Rats received an intravenous infusion of Nic (90 µg/kg, over 60 s) and extracellular NE levels in the PVN were determined by in vivo microdialysis. Immediately after Nic administration, the rats were bilaterally treated with acupuncture at acupoint HT7 (Shen-Men) or PC6 (Nei-Guan), or a non-acupoint (tail) for 60 s. Acupuncture at HT7, but not at PC6 or the tail, significantly reduced Nic-induced NE release. However, this was abolished by a post-acupuncture infusion of either NMDA or sodium nitroprusside into the NTS. Additionally, acupuncture at HT7, but not the control points, prevented Nic-induced plasma corticosterone secretion and inhibited Nic-induced increases in the phosphorylation of neuronal nitric oxide synthase (nNOS) and endothelial NOS in the NTS. These findings suggest that acupuncture at HT7 reduces Nic-induced NE release in the PVN via inhibition of the solitary NMDAR/NOS pathway.

Synergistic protective effect of folic acid and vitamin B12 against nicotine-induced oxidative stress and apoptosis in pancreatic islets of the rat.

CONTEXT: Nicotine is an abundant and most significant component of cigarette smoke. Epidemiological evidence strongly suggests an association between cigarette smoking and pancreatic injury, although effects of smoking on endocrine pancreas are still controversial. OBJECTIVE: We examined the impact and underlying mechanisms of action of folic acid and vitamin B12 on nicotine-induced damage in pancreatic islets of rats. MATERIALS AND METHODS: Male Wistar rats were treated with nicotine (3 mg/kg body weight/d, intraperitonealy) with or without folic acid (36 µg/kg body weight/d, orally) and vitamin B12 (0.63 µg/kg body weight/d, orally) for 21 d. Fasting blood glucose, oral glucose tolerance test, HBA1c, insulin, oxidative stress parameters, proinflammatory cytokines, and CRP level were measured. Histological evaluation, TUNEL assay, and immunohistochemical staining of NF-κB and caspase-3 were also performed. RESULTS: Folic acid and vitamin B12 blunted the nicotine-induced impairment in fasting blood glucose (51-56% recovery), HbA1c (64-76% recovery), oral glucose tolerance, insulin level (23-40% recovery), and islet cell counts (26-74% recovery) in rats. Moreover, folic acid in combination with vitamin B12 also attenuated the nicotine-induced changes in markers of oxidative stress (17-88% recovery), TNF-α (40-99% recovery), and IL-6 level (47-65% recovery), CRP level (59-73% recovery), expression of NF-κB and caspase-3, and apoptosis in pancreatic islet cells. DISCUSSION AND CONCLUSION: The present study shows that folic acid and vitamin B12 supplementation can reduce nicotine-induced impairment in glucose homeostasis and apoptosis and damage of pancreatic islet cells by modulating oxidative stress, levels of proinflammatory cytokines, and expression of NF-κB.

Nuciferine, extracted from Nelumbo nucifera Gaertn, inhibits tumor-promoting effect of nicotine involving Wnt/ß-catenin signaling in non-small cell lung cancer.

ETHNOPHARMACOLOGICAL RELEVANCE: The leaves of Nelumbo nucifera Gaertn are recorded in the earliest written documentation of traditional Chinese medicinal as "Ben Cao Gang Mu", a medicinal herb for blood clotting, dysentery and dizziness. Recently, nuciferine (NF), one of N. nucifera Gaertn leaf extracts has been shown to possess several pharmacological properties, including anti-viral and anti-cancer. The aim of this study is to investigate the underlying molecular mechanism of the anti-cancer activity of NF in NSCLC progression induced by nicotine MATERIALS AND METHODS: The effect of NF on proliferation of A549 (human lung adenocarcinoma epithelial cell line) pretreated with or without nicotine was detected by tumor cell proliferation assay. TOP-Flash reporter assay was applied to investigate the activity of Wnt/ß-catenin signaling in tumor cells in the presence of NF and/or nicotine. Apoptosis was measured using a FITC-Annexin V and PI detection kit by flow cytometry. In addition, mRNA or protein expression levels were respectively tested by quantitative RT-PCR or western blot. In vivo experiments, tumor samples were fixed in formalin and embedded in paraffin for additional analyses by immunohistochemistry and TUNEL staining. RESULTS: NF significantly inhibited the proliferation of NSCLC cells in the presence of nicotine, suppressed the activity of Wnt/ß-catenin signaling, enhanced the stabilization of Axin, and induced apoptosis. NF down-regulated the expression levels of ß-catenin and its downstream targets including c-myc, cyclin D and VEGF-A. NF also decreased the ratio of Bcl-2/Bax, which may explain the pro-apoptosis effect of NF. In tumor xenograft nude mice, NF not only inhibited the growth of non-small cell lung cancer (NSCLC) cells, but also remarkably alleviated the injury induced by nicotine in liver function. CONCLUSIONS: NF has the remarkable effect to inhibit nicotine-induced NSCLC progression, which was due to its ability to reduce the activity of Wnt/ß-catenin signaling. Thus, the work stated here emphasizes the importance of this traditional medicine and presents a potential novel alternative to NSCLC prevention and therapy.

[Recent progress in vaccines against nicotine addiction].

Tobacco smoking is a global healthcare problem that poses a substantial and costly health burden. Nicotine is the major constituent responsible for the addiction to tobacco. Current strategies helping tobacco smokers have limited utility in increasing rates of smoking cessation, consequently indicating the need for alternative therapies. A novel therapeutic method is vaccination against nicotine. Nicotine vaccine can generate specific antibodies that can sequester nicotine from cigarette smoke in the blood, and prevent its access to the brain and minimize positive reinforcing effects, which may help smokers to stop smoking. The vaccine will have great potential for the treatment of nicotine addiction and for relapse prevention. Here we will review the current status of vaccines against nicotine addiction and discuss the problems associated with the development of nicotine vaccines.

MK-801 disrupts and nicotine augments 40 Hz auditory steady state responses in the auditory cortex of the urethane-anesthetized rat.

Patients with schizophrenia show marked deficits in processing sensory inputs including a reduction in the generation and synchronization of 40 Hz gamma oscillations in response to steady-state auditory stimulation. Such deficits are not readily demonstrable at other input frequencies. Acute administration of NMDA antagonists to healthy human subjects or laboratory animals is known to reproduce many sensory and cognitive deficits seen in schizophrenia patients. In the following study, we tested the hypothesis that the NMDA antagonist MK-801 would selectively disrupt steady-state gamma entrainment in the auditory cortex of urethane-anesthetized rat. Moreover, we further hypothesized that nicotinic receptor activation would alleviate this disruption. Auditory steady state responses were recorded in response to auditory stimuli delivered over a range of frequencies (10-80 Hz) and averaged over 50 trials. Evoked power was computed under baseline condition and after vehicle or MK-801 (0.03 mg/kg, iv). MK-801 produced a significant attenuation in response to 40 Hz auditory stimuli while entrainment to other frequencies was not affected. Time-frequency analysis revealed deficits in both power and phase-locking to 40 Hz. Nicotine (0.1 mg/kg, iv) administered after MK-801 reversed the attenuation of the 40 Hz response. Administered alone, nicotine augmented 40 Hz steady state power and phase-locking. Nicotine's effects were blocked by simultaneous administration of the α4ß2 antagonist DHßE. Thus we report for the first time, a rodent model that mimics a core neurophysiological deficit seen in patients with schizophrenia and a pharmacological approach to alleviate it.

Dose-dependent effects of nicotine on proliferation and differentiation of human bone marrow stromal cells and the antagonistic action of vitamin C.

A range of biological and molecular effects caused by nicotine are considered to effect bone metabolism. Vitamin C functions as a biological antioxidant. This study was to evaluate the in vitro effects of nicotine on human bone marrow stromal cells and whether Vitamin C supplementation show the antagonism action to high concentration nicotine. We used CCK-8, alkaline phosphatase (ALP) activity assay, Von Kossa staining, real-time polymerase chain reaction and Western Blot to evaluate the proliferation and osteogenic differentiation. The results indicated that the proliferation of BMSCs increased at the concentration of 50, 100 ng/ml, got inhibited at 1,000 ng/ml. When Vitamin C was added, the OD for proliferation increased. For ALP staining, we found that BMSCs treated with 50 and 100 ng/ml nicotine showed a higher activity compared with the control, and decreased at the 1,000 ng/ml. Bone morphogenetic protein-2 (BMP-2) expression and the calcium depositions decreased at 100 and 1,000 ng/ml nicotine, while the addition of Vitamin C reversed the down regulation. By real-time PCR, we detected that the mRNA expression of collagen type I (COL-I) and ALP were also increased in 50 and 100 ng/ml nicotine groups (P < 0.05), while reduced at 1,000 ng/ml (P < 0.05). When it came to osteocalcin (OCN), the changes were similar. Taken all together, it is found that nicotine has a two-phase effect on human BMSCs, showing that low level of nicotine could promote the proliferation and osteogenic differentiation while the high level display the opposite effect. Vitamin C could antagonize the inhibitory effect of higher concentration of nicotine partly.

Novel use of a lipid-lowering fibrate medication to prevent nicotine reward and relapse: preclinical findings.

Experimental drugs that activate α-type peroxisome proliferator-activated receptors (PPARα) have recently been shown to reduce the rewarding effects of nicotine in animals, but these drugs have not been approved for human use. The fibrates are a class of PPARα-activating medications that are widely prescribed to improve lipid profiles and prevent cardiovascular disease, but these drugs have not been tested in animal models of nicotine reward. Here, we examine the effects of clofibrate, a representative of the fibrate class, on reward-related behavioral, electrophysiological, and neurochemical effects of nicotine in rats and squirrel monkeys. Clofibrate prevented the acquisition of nicotine-taking behavior in naive animals, substantially decreased nicotine taking in experienced animals, and counteracted the relapse-inducing effects of re-exposure to nicotine or nicotine-associated cues after a period of abstinence. In the central nervous system, clofibrate blocked nicotine's effects on neuronal firing in the ventral tegmental area and on dopamine release in the nucleus accumbens shell. All of these results suggest that fibrate medications might promote smoking cessation. The fact that fibrates are already approved for human use could expedite clinical trials and subsequent implementation of fibrates as a treatment for tobacco dependence, especially in smokers with abnormal lipid profiles.

Hippophae rhamnoides attenuates nicotine-induced oxidative stress in rat liver.

The effects of vitamin E and Hippophae rhamnoides L. (Elaeagnaceae) extract (HRe-1) on nicotine-induced oxidative stress in rat liver were investigated. Four groups, eight rats each, were used in this study, and the supplementation period was 3 weeks. The groups were: nicotine (0.5 mg/kg/day, intraperitoneal (i.p.)); nicotine plus vitamin E (75 mg/kg/day, intragastric (i.g.)); nicotine plus HRe-1 (250 mg/kg/day, i.g.); and the control group. The malondialdehyde and nitric oxide levels, glutathione peroxidase, glutathione S-transferase, glutathione reductase, superoxide dismutase, and total and non-enzymatic superoxide scavenger activities were measured spectrophotometrically in supernatants of the tissue homogenates. Nicotine increased the malondialdehyde level in liver tissue compared with control. This nicotine-induced increase in lipid peroxidation was prevented by both vitamin E and HRe-1. Superoxide dismutase activity was higher in the nicotine plus vitamin E-supplemented group compared with nicotine and control groups. Glutathione reductase activity was higher in the nicotine group compared with the control group. However, glutathione peroxidase activity in the control group was higher than the levels in the nicotine, and the nicotine plus HRe-1 supplemented groups. The nitric oxide level was higher in the nicotine group compared with all other groups. Total and non-enzymatic superoxide scavenger activities and glutathione S-transferase activity were not affected by any of the treatments. Our results suggest that Hippophae rhamnoides extract as well as vitamin E can protect the liver against nicotine-induced oxidative stress.

Deleterious effects of nicotine on the ultrastructure of oocytes: role of gamma-tocotrienol.

BACKGROUND: Previous studies have shown that nicotine enhances oxidative DNA damage and leads to increased lipid peroxidation, which affects embryo development. The present study investigated the effect of daily supplementation of gamma-tocotrienol on oocytes of nicotine-treated mice. MATERIAL/METHODS: Immature female mice (18-25 g) were divided into three groups. For 30 days, group A (control group) received saline (0.2 ml/day s.c.), group B nicotine (5 mg/kg/day s.c. in saline), and group C nicotine with gamma-tocotrienol (60 mg/kg/day p.o.). The animals were superovulated following these schedules. RESULTS: Scanning electron microscopy (SEM) showed that the nicotine-treated oocytes appeared nonspherical with rough surface and the zona pellucida (zp) was torn and became irregular. Supplementation with gamma-tocotrienol in the nicotine-treated mice retained the spherical shape of the oocytes with intact zp; however, the surfaces of the oocytes remained irregular and rough. Transmission electron microscopy (TEM) following chronic nicotine treatment showed loosening of the boundary and tearing of the zp. The perivitelline space was also widened. The cytoplasm of the oocytes retained abundant rough endoplasmic reticulum (rER) with numerous vesicles. Mitochondria were highly dense, with no cristae. The administration of gamma-tocotrienol partially reduced the detrimental effects of nicotine by retaining the smooth boundary of the zp with the tight perivitelline space. There was less rER with no visible vesicle and a lower amount of dense mitochondrial matrix. CONCLUSIONS: This study documented that chronic nicotine treatment adversely affects the ultrastructure of oocytes, while gamma-tocotrienol treatment at least minimizes the nicotine-induced damage to oocytes.

Beneficial effects of tocotrienol and tocopherol on bone histomorphometric parameters in sprague-dawley male rats after nicotine cessation.

This study was conducted to determine the effectiveness of three forms of vitamin E supplements following nicotine treatment on bone histomorphometric parameters in an adult male rat model. Rats were divided into seven groups: baseline (B, killed without treatment), control (C, normal saline for 4 months), nicotine (N, nicotine for 2 months), nicotine cessation (NC), tocotrienol-enhanced fraction (TEF), gamma-tocotrienol (GTT), and alpha-tocopherol (ATF). Treatments for the NC, TEF, GTT, and ATF groups were performed in two phases. For the first 2 months they were given nicotine (7 mg/kg), and for the following 2 months nicotine administration was stopped and treatments with respective vitamin E preparations (60 mg/kg) were commenced except for the NC group, which was allowed to recover without treatment. Rats in the N and NC groups had lower trabecular bone volume, mineral appositional rate (MAR), and bone formation rate (BFR/BS) and higher single labeled surface and osteoclast surface compared to the C group. Vitamin E treatment reversed these nicotine effects. Both the TEF and GTT groups, but not the ATF group, had a significantly higher trabecular thickness but lower eroded surface (ES/BS) than the C group. The tocotrienol-treated groups had lower ES/BS than the ATF group. The GTT group showed a significantly higher MAR and BFR/BS than the TEF and ATF groups. In conclusion, nicotine induced significant bone loss, while vitamin E supplements not only reversed the effects but also stimulated bone formation significantly above baseline values. Tocotrienol was shown to be slightly superior compared to tocopherol. Thus, vitamin E, especially GTT, may have therapeutic potential to repair bone damage caused by chronic smoking.

Dimethyl sulfoxide as a block to the deleterious effect of nicotine in a random skin flap in the rat.

BACKGROUND: In plastic surgery, a causal relationship between heavy smoking and flap necrosis has been shown. The deleterious effect of nicotine in random skin flaps in rats has also been proven, being related to vasoconstriction and possibly reactive oxygen species. This study aimed to verify the capacity of dimethyl sulfoxide, an antioxidant, to block the deleterious effect of nicotine in a random skin flap. METHODS: Fourteen adult male Wistar-EPM rats were distributed at random into two groups of seven animals. The nicotine group received this drug subcutaneously (1.2 mg/kg/day), for 1 week before flap elevation. The nicotine plus dimethyl sulfoxide group followed the same routine. Five minutes before the surgical procedure, rats in the nicotine group received distilled water orally and rats in the nicotine plus dimethyl sulfoxide group received dimethyl sulfoxide orally (2 ml/kg). Blood and skin tissue samples were collected to allow determination of malondialdehyde levels. RESULTS: The nicotine group had a mean value of 40.2 percent and the nicotine plus dimethyl sulfoxide group had a mean value of 20.6 percent necrosis (p = 0.009). Malondialdehyde levels in both serum and skin samples were lower in the animals that received dimethyl sulfoxide. CONCLUSION: The deleterious effect of nicotine was effectively blocked by dimethyl sulfoxide.

N-n-alkylnicotinium analogs, a novel class of antagonists at alpha 4 beta 2* nicotinic acetylcholine receptors: inhibition of S(-)-nicotine-evoked 86Rb+ efflux from rat thalamic synaptosomes.

Pyridine N-n-alkylation of S(-)-nicotine (NIC) affords N-n-alkylnicotinium analogs, previously shown to competitively inhibit [(3)H]NIC binding and interact with alpha4beta2* nicotinic receptors (nAChRs). The present study determined the ability of the analogs to inhibit NIC-evoked (86)Rb(+) efflux from rat thalamic synaptosomes to assess functional interaction with alpha4beta2* nAChRs. In a concentration-dependent manner, NIC evoked (86)Rb(+) efflux (EC(50) = 170 nmol/L). Analog-induced inhibition of NIC-evoked (86)Rb(+) efflux varied over a approximately 450-fold range. Analogs with long n-alkyl chain lengths (C(9)-C(12)) inhibited efflux in the low nmol/L range (IC(50) = 9-20 nmol/L), similar to dihydro-beta-erythroidine (IC(50) = 19 nmol/L). Compounds with shorter n-alkyl chain lengths (C(1)-C(8)) produced inhibition in the low micromol/L range (IC(50) = 3-12 micromol/L). C(10) and C(12) analogs completely inhibited NIC-evoked efflux, whereas C(1-9) analogs produced maximal inhibition of only 10% to 60%. While the C(10) analog N-n-decylnicotinium iodide (NDNI) did not produce significant inhibition of NIC-evoked dopamine release in previously reported studies, NDNI possesses high affinity for [(3)H]NIC binding sites (K(i) = 90 nmol/L) and is a potent and efficacious inhibitor of NIC-evoked (86)Rb(+) efflux as demonstrated in the current studies. Thus, NDNI is a competitive, selective antagonist at alpha4beta2* nAChRs.

Effects of Salvia officinalis L. (sage) leaves on memory retention and its interaction with the cholinergic system in rats.

OBJECTIVE: The leaves of sage (Salvia officinalis L., Lamiaceae) are reported to have a wide range of biological activities, such as anti-bacterial, fungistatic, virustatic, astringent, eupeptic and anti-hydrotic effects. To determine the mnemogenic effect of sage leaves, we investigated the effects of ethanolic extract of sage leaves and its interaction with cholinergic system on memory retention of passive avoidance learning in rats. METHODS: Post-training intracerebroventricular (i.c.v.) injections were carried out in all the experiments except ethanolic extract (i.p. intraperitoneally). RESULTS: Administration of ethanolic extract (50 mg/kg), pilocarpine (0.5 and 1 mg/rat), the muscarinic cholinoceptor agonist, and nicotine (0.1 and 1 microg/rat) increased, while mecamylamine (1, 5 microg/rat), the muscarinic cholinoceptor antagonist, and mecamylamine (0.01 and 0.1 microg/rat), the nicotine cholinoceptor antagonist decreased memory retention in rats. Activation of muscarinic cholinoceptors by pilocarpine potentiated the response of ethanolic extract. Also, pharmacological blockade of scopolamine attenuated potentiating effect of ethanolic extract. Activation of nicotinic cholinoceptor by nicotine potentiated the response of ethanolic extract. Blockade of nicotinic cholinoceptor by mecamylamine attenuated the response of ethanolic extract. CONCLUSION: It is concluded that the ethanolic extract of salvia officinalis potentiated memory retention and also it has an interaction with muscarinic and nicotinic cholinergic systems that is involved in the memory retention process.

Effects of nicotine-specific antibodies, Nic311 and Nic-IgG, on the transfer of nicotine across the human placenta.

The adverse effects of smoking during pregnancy on fetal development are, in part, due to nicotine. These effects may be due to the actions of nicotine in fetal circulation or on placental functions. In pregnant rats, vaccination with a nicotine immunogen reduces the transfer of nicotine from the maternal to fetal circulation. However, extrapolation of these results to pregnant women might not be valid due to the well-recognized differences between human and rat placentas. In the current investigation, the effects of nicotine-specific antibodies on the transfer of nicotine from the maternal to fetal circuit of the dually perfused human placental lobule were determined. Two types of nicotine-specific antibodies were investigated; nicotine-specific mouse monoclonal antibody (Nic311, K(d) for nicotine 60nM) and IgG from rabbits vaccinated with a nicotine immunogen (Nic-IgG, K(d) 1.6nM). Transfer of the antibodies from maternal to fetal circuits was negligible. Both rabbit Nic-IgG and, to a lesser extent, mouse monoclonal Nic311 significantly reduced nicotine transfer from the maternal to fetal circuit as well as the retention of the drug by placental tissue. These effects were mediated by a substantial increase in the protein binding of nicotine and a reduction in the unbound nicotine concentration. Therefore, the data cited in this report suggest that the use of nicotine-specific antibodies might reduce fetal exposure to the drug, and that antibody affinity for nicotine is a key determinant of the extent of nicotine transfer.

Chronic nicotine toxicity is prevented by aqueous garlic extract.

Based on the potent antioxidant effects of garlic, we investigated the putative protective role of aqueous garlic extract (AGE) against nicotine-induced oxidative organ damage. Male Wistar albino rats (200-250 g) were injected with nicotine hydrogen bitartrate (0.6 mg/kg; i.p.) alone or with aqueous garlic extract (125 mg/kg; i.p.) for 21 days. At the end of the experimental period (22nd day) rats were killed by decapitation. The aorta, heart, kidney and urinary bladder tissues were taken for the determination of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen contents. Blood urea nitrogen (BUN) and creatinine concentrations and lactate dehydrogenase (LDH) levels in blood were measured for the evaluation of renal functions and tissue damage, respectively. Tissues were also examined microscopically. The decrease in GSH levels and increases in MDA level, MPO activity and collagen contents induced by chronic nicotine administration indicated that tissue injury involves free radical formation. Treatment of rats with AGE restored the reduced GSH levels while it decreased MDA levels as well as MPO activity. Increased collagen contents of the tissues by chronic nicotine were reversed back to the control levels with AGE. Since AGE administration reversed these oxidant responses, improved renal function and histological damage, it seems likely that AGE protects the tissues against nicotine-induced oxidative damage.

Taurine treatment protects against chronic nicotine-induced oxidative changes.

Experiments have shown that chronic nicotine administration caused oxidative damage in various organs by increasing lipid peroxidation products and decreasing the activity of endogenous antioxidants. The aim of this study was to investigate the effects of taurine treatment on nicotine-induced oxidative changes in rat thoracic aorta and heart and to explore the possible mechanisms of action. Male Wistar albino rats (200-250 g) were injected with nicotine hydrogen bitartrate (0.6 mg/kg; i.p.) or saline for 21 days. Taurine was administered (50 mg/kg; i.p.) alone or along with nicotine injections. After decapitation, the thoracic aorta and heart tissues were excised. The aorta was used for in vitro contractility studies or stored along with the heart samples for the measurement of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen content. Tissue samples were also examined histologically. Serum samples were stored for the measurement of MDA, GSH and lactate dehydrogenase (LDH) activity. Chronic nicotine treatment impaired both the contraction and relaxation responses of the aortic rings to phenylephrine and acetylcholine, respectively. It increased lipid peroxidation, MPO levels and tissue collagen content of both aorta and heart samples. Taurine supplementation to nicotine-treated animals reversed the contractile dysfunction and restored the endogenous GSH levels and decreased high lipid peroxidation and MPO activities in both tissues. These data suggest that taurine supplementation effectively attenuates the oxidative damage because of chronic nicotine administration possibly by its antioxidant effects.

Nicotine enhancement of dopamine release by a calcium-dependent increase in the size of the readily releasable pool of synaptic vesicles.

A major factor underlying compulsive tobacco use is nicotine-induced modulation of dopamine release in the mesolimbic reward pathway (Wise and Rompre, 1989). An established biochemical mechanism for nicotine-enhanced dopamine release is by activating presynaptic nicotinic acetylcholine receptors (nAChRs) (Wonnacott, 1997). Prolonged application of 10(-7) to 10(-5) m nicotine to striatal synaptosomes promoted a sustained efflux of [3H]dopamine. This nicotine effect was mediated by non-alpha7 nAChRs, because it was blocked by 5 mum mecamylamine but was resistant to 100 nm alpha-bungarotoxin (alphaBgTx). Dopamine release was diminished by omitting Na+ or by applying peptide calcium channel blockers, indicating that nAChRs trigger release by depolarizing the nerve terminals. However, because alpha7 receptors rapidly desensitize in the continuous presence of agonists, a repetitive stimulation protocol was used to evaluate the possible significance of desensitization. This protocol produced a transient increase in [3H]dopamine released by depolarization and a significant increase in the response to hypertonic solutions that measure the size of the readily releasable pool (RRP) of synaptic vesicles. The nicotine-induced increase in the size of the readily releasable pool was blocked by alphaBgTx and by the calmodulin antagonist calmidazolium, suggesting that Ca2+ entry through alpha7 nAChRs specifically enhances synaptic vesicle mobilization at dopamine terminals. Thus, nicotine enhances dopamine release by two complementary actions mediated by discrete nAChR subtypes and suggest that the alpha7 nAChR-mediated pathway is tightly and specifically coupled to refilling of the RRP of vesicles in dopamine terminals.

Inhibition of nicotine-induced toxicity by curcumin and curcumin analog: a comparative study.

The present study was undertaken to evaluate the effects of curcumin and curcumin analog on blood oxidant-antioxidant status during nicotine-induced toxicity in male Wistar rats. Lung toxicity was induced by subcutaneous injection of nicotine at a dose of 2.5 mg/kg of body weight (5 days a week, for 22 weeks). The enhanced circulatory lipid peroxides in nicotine-treated rats was accompanied by a significant decrease in the levels of ascorbic acid, vitamin E, reduced glutathione, glutathione peroxidase, superoxide dismutase, and catalase. There was a reduction in the levels of zinc with an elevation of copper and ferritin in nicotine-treated rats. Administration of curcumin and curcumin analog significantly lowered the lipid peroxidation and enhanced the antioxidant status with modulation in the levels of zinc, copper, and ferritin. However, the effect was more significant in curcumin analog-treated rats than in curcumin-treated rats. The results of the present study suggest that curcumin and curcumin analog exert their protective effects by modulating the extent of lipid peroxidation and enhancing the antioxidant status.

Characterization of the effects of bupropion on the reinforcing properties of nicotine and food in rats.

Bupropion is an atypical antidepressant drug that is the only nonnicotine-based prescription medicine approved for smoking cessation by the Food and Drug Administration. The aim of the present experiments was to investigate the effects of bupropion (5-40 mg/kg) on the reinforcing properties of nicotine and food in rats. The effects of bupropion were studied under two schedules of reinforcement: a fixed ratio 5 time-out 20-sec (FR5 TO20 s) and a progressive ratio (PR). Rats were trained to respond for nicotine (0.01 or 0.03 mg/kg/infusion, free base) or food under the FR5 TO20 s schedule. Pretreatment with the highest dose of bupropion (40 mg/kg) resulted in a significant reduction (approximately 50%) of nicotine intake in rats self-administering 0.03 mg/kg/infusion of nicotine. The same dose of bupropion also decreased (approximately 40%) the self-administration of 0.01 mg/kg/infusion of nicotine, but this effect did not reach statistical significance. Pretreatment with bupropion slightly (approximately 15%) reduced responding for food under the FR5 TO20 s schedule. Finally, pretreatment with bupropion did not affect the self-administration of nicotine (0.03 mg/kg/infusion) under a PR schedule, but dose-dependently increased responding for food under the same PR schedule. These findings indicate that a high dose of bupropion decreases the reinforcing properties of nicotine as measured under an FR schedule, while having no apparent effects on breaking points for nicotine under a PR schedule that reflects both the reinforcing properties and the motivation to obtain nicotine.

Inhibitory effect of Sejin-Eum I/II on nicotine- and cigarette extract-induced cytotoxicity in human lung fibroblast.

Nicotine is a major pharmacologically active component of cigarette smoke. Excessive cigarette smoking is harmful to lung. Sejin-Eum (SJE) I is composed of various Oriental medicines, and SJE II is SJE I plus seeds of Avena sativa (Gramineae) that reduces the craving for cigarette in man. In this study, we have examined whether an aqueous extract of SJE I/II inhibits nicotine- or cigarette extract (CE)-induced cytotoxicity in human embryonic lung fibroblast, MRC-9. Assessment of cell viability using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay indicated that SJE I/II (500 and 1000 microg/ml) not only inhibited nicotine-induced cytotoxicity but also had significantly proliferous effect on MRC-9. However, SJE I/II had little effect on inhibition of CE-induced cytotoxicity. These results suggest the possibility that the use of SJE I/II may be useful for improvement of many symptoms by nicotine.