A study on the agents that reduces the nicotine induced nicotinic receptor density in wistar rats

The most important substance causing addiction towards cigarette is nicotine. Nicotine abstinence causes withdrawal symptoms in smokers. It is not just nicotine, along with it is the upregulation of nicotinic receptor density (NRD) that leads to addiction. All together makes nicotine deaddiction the most difficult aspect. Nicotine receptor density increases as long as the person is exposed to nicotine. When once the NRD is initiated by nicotine, later though you stop smoking, the increased nicotine receptors create an urge to smoke. Hence the person feels to smoke for satisfying the nicotine receptors. The smokers may attempt to quit smoking but the NRD will create an urge for nicotine again. One cannot completely quit smoking or cannot stop taking nicotine, until the NRD is reduced to normal. In our present study we have studied the effect of citric acid and tyrosine on decreasing nicotinic receptor density. We have induced the nicotinic receptor density to raise and studied the citric acid and tyrosine’s effect in maintaining the NRD closer to normal. The study concludes that citric acid and tyrosine have reduced the NRD significantly. This can control withdrawal symptoms and can stop craving for nicotine and finally can lead to cessation of smoking and from taking nicotine therapy.

Screening and evaluation of ethanolic extract from Casuarina equisetifolia inflorescence on isolated chick rectum, frog rectum and frog rectus abdominus muscle for identification of muscarinic and nicotinic receptor’s action

The present experiments were undertaken to justify the use of an ethanolic extract from inflorescence of Casuarina equisetifolia, Family: Casuarinaceae, influencing the nicotine responses on isolated chick rectum and frog rectum (Smooth Muscles) and frog rectus abdominus muscle (Skeletal Muscle). The isolated tissues were mounted in organ bath filled with physiological solution and was suitably aerated. After equilibration, responses were taken to different doses of nicotine (log doses) till a ceiling response was obtained. A sub-maximal dose of nicotine was selected and responses to this dose was taken and ensured that there is reproducibility of response. The drum was allowed to move for 1min., different concentrations of extracts into the organ baths were added and allowed to act for 1min without flushing the baths, then the sub-maximal dose of nicotine was added and allowed to act for 1min. this procedure was repeated (without extract) till the original response was obtained. The inference drawn from these experiments, the ethanolic extract of inflorescence of Casuarina equisetifolia antagonised the action of nicotine on isolated chick rectum, relaxed the effect of nicotine on frog rectum and it potentiated the effect of nicotine on frog rectus abdominus muscle. The nicotine receptors of rectus abdominus is activated, perhaps by the prevention of hydrolysis of acetylcholine by the extract. Based on the results obtained from the isolated chick rectum the ethanolic extract is having antinicotinic activity and it may act on the nicotinic acetylcholine receptors (nAChRs) as well as muscarinic acetylcholine receptors (mAChRs) on other isolated tissues. The extract might contain ganglionic blocking activity or non-specific activity or membrane stabilising activity also. Keywords: Nicotine, Ethanolic extract, Inflorescence of Casuarina equisetifolia, Isolated Chick Rectum, Isolated Frog Rectum and Isolated Frog Rectus Abdominus Muscle.

Abstract 147: Role of Nicotine in the Development of Intracranial Aneurysm Rupture

Background: Nicotine is one of main chemicals of tobacco smoke and promotes atherosclerosis and stroke. Tobacco smoke is considered an independent risk factor for intracranial aneurysm formation, growth, and rupture. There are mainly 5 subtypes of nicotine receptors. Roles of alpha7 nicotinic acetylcholine receptor (α7nAChR) in inflammation and vascular remodeling are diverse and context-dependent. Notably, endothelial α7nAChR is considered to mediate nicotine-induced inflammation. Activation of endothelial α7nAChR by nicotine may promote aneurysm rupture by increasing the aneurysm wall inflammation. Using a mouse model of intracranial aneurysm, we examined effects of nicotine in aneurysm rupture. Moreover we investigated potential roles of α7nAChR stimulation by nicotine in the pathophysiology of intracranial aneurysms. Methods: Intracranial aneurysms were induced by a combination of elastase injection into the cerebrospinal fluid and deoxycorticosteron acetate-salt (DOCA-salt) hypertension in male mice. Mice were treated with (1) nicotine (5 mg/kg/day, n=25); (2) saline sc (n=22) for three weeks after aneurysm induction. To investigate the effect of α7nAChR, mice were treated with (1) saline sc + saline ip (n=11); (2) saline sc + α7nAChR antagonist (Methyllycaconitine, MLA 5mg/kg/day) ip (n=13); (3) nicotine (5 mg/kg/day, sc, 28 days) + saline ip (n=18); (4) nicotine sc + MLA ip (n=18). Results: Nicotine alone significantly increased aneurysmal rupture compared with saline treatment (89% vs 46%, p=0.009). While α7nAChR antagonist did not affect the incidence of aneurysm or rupture rates, the α7nAChR antagonist significantly reduced the deleterious effect of nicotine as indicated by the reduction of the rupture rates (41% vs 100%: nicotine sc + MLA ip group vs nicotine sc + saline ip group, p=0.027). Conclusion: Our data indicate the promotion of aneurysm rupture by nicotine may be mediated by its stimulation of alpha7nAChR.

A case of a varenicline-induced mania in a patient with the history of depression

IntroductionVarenicline is an alpha 4 beta 2 nicotinic receptor partial agonist with dopaminergic effects, approved for smoking cessation. The complex interactions and modulations of serotonin and nicotine receptors caused by varenicline may cause mania by its serotonin agonist activity and by its release of dopamine in the striatum. We report a case of a varenicline-induced mania with the history of depression.CaseA 38-year-old female, with the history of depression and have been using sertraline 50 mg/day for a year, admitted for grandiose delusions, decreased need for sleep, increased amount and rapid speech, and agitation. These symptoms began 1 week after she started taking varenicline as prescribed for smoking cessation. Young Mania Score (YMS) was 32. She discontinued sertraline and varenicline after 1 week of use but symptoms of mania continued. The patient smoked about 20 cigarettes a day for more than 10 years. She had a positive history of depression in her family. Her lab work up was unremarkable; including negative urine toxicology and brain CT scan. The patient met DSM-5 criteria for a manic episode and was started on olanzapine 10 mg/day and quetiapine 100 mg/day. The patient's symptoms gradually improved within 1 week with attainment of euthymic mood, improved sleep, and resolution of grandiosity. YMS was 7.ConclusionBased on this case it might be suggested that patient's and family's psychiatric history should be assessed cautiously before prescribing varenicline for smoking cessation due to development of mood symptoms.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Characterization of the adverse effects of nicotine on placental development: in vivo and in vitro studies

In utero exposure to nicotine is associated with increased risk of numerous adverse fetal and neonatal outcomes, which suggests that it acts directly to affect placental development and the establishment of the fetomaternal circulation (FC). This study used both in vivo [Wistar rats treated with 1 mg/kg nicotine from 2 wk prior to mating until gestational day (GD) 15] and in vitro (RCHO-1 cell line; treated with 10−9 to 10−3M nicotine) models to examine the effects of nicotine on these pathways. At GD 15, control and treated placentas were examined for the impact of nicotine on 1) trophoblast invasion, proliferation, and degree of hypoxia, 2) labyrinth vascularization, 3) expression of key genes of placental development, and 4) expression of placental angiogenic factors. The RCHO-1 cell line was used to determine the direct effects of nicotine on trophoblast differentiation. Our in vivo experiments show that nicotine inhibits trophoblast interstitial invasion, increases placental hypoxia, downregulates labyrinth vascularization as well as key transcription factors Hand1 and GCM1, and decreases local and circulating EG-VEGF, a key placental angiogenic factor. The in vitro experiments confirmed the inhibitory effects of nicotine on the trophoblast migration, invasion, and differentiation processes and demonstrated that those effects are most likely due to a dysregulation in the expression of nicotine receptors and a decrease in MMP9 activity. Taken together, these data suggest that adverse effects of maternal smoking on pregnancy outcome are due in part to direct and endocrine effects of nicotine on the main processes of placental development and establishment of FC.

Abstract 483: The Signaling Pathways of Nicotine-induced ERK1/2 Phosphorylation in Rat Mesangial Cells

Tobacco smoking is associated with accelerated progression of chronic kidney disease of different etiologies including diabetes and hypertension. However, the mechanisms involved are not well understood. We have previously reported that nicotine, a biologically active compound present in high concentrations in tobacco, induces cell proliferation and fibronectin production in mesangial cells which are prevented by ERK1/2 inhibition (AJP’05). In these studies we determined whether rat mesangial cells (MC) express nicotine receptors and characterized the signaling pathways that lead to ERK1/2 phosphorylation in response to nicotine. MC were grown in DMEM with 15% FBS in the presence of 0.4 mg/ml G418 and starved for 24 hours in DMEM without FBS before treatment. We first demonstrated that MC are endowed with several nicotinic Ach receptor (nAChR) subunits including α2-7 and β1-4 as assessed by western blot. Treatment of rat MC with nicotine at 10 -7 M caused a time-dependent ERK1/2 phosphorylation which peaked after 10 min of stimulation( N=3). Several protein kinase inhibitors were then used to identify the upstream kinases that mediate nicotine-induced ERK1/2 phosphorylation. The calcium/calmodulin-dependent protein kinase II (CaMKII) inhibitor KN93 (10 -7 M) decreased the ERK1/2 phosphorylation level by ∼57% (0.41 of 0.95) as compared to nicotine. The PKC inhibitor Go6983 at 10 -9 M, the PKA inhibitor H89 (10 -8 M) and the EGFR inhibitor AG 1478 (10 -7 M) also inhibited ERK1/2 phosphorylation by 60% (0.38 of 0.95), 48% (0.63 of 1.20) and 68% (0.40 of 1.23) respectively as compared to nicotine. Given the role of the nicotine receptors as agonist-regulated Ca 2+ channels, we determined the effects of Ca 2+ channel blockade on nicotine induced ERK1/2 phosphorylation. Treatment of MC with the calcium channel Verapamil (10 -9 M) resulted in 33% (0.49 of 0.73) inhibition of ERK1/2 phosphorylation as compared to nicotine. In summary, we have determined in these studies that rat MC are endowed with several nAChR subunits and that ERK1/2 phosphorylation in response to nicotine requires CaMK II, PKA, PKC and EGFR. In addition, we have demonstrated that these effects require Ca 2+ consistent with the role of the nAChR as agonist-regulated Ca 2+ channels in MC.