Noradrenergic-induced expression of c-fos in rat cortex: neuronal localization.

β Adrenoceptors in the rat forebrain have been shown to exist predominantly on astrocytes. Studies were undertaken to determine whether the cellular localization of c-fos expression caused by the activation of brain β receptors would have a similar cellular localization. Double label light and electron microscopic immunohistochemical experiments with a glial (glial fibrillary acidic protein, GFAP) and neuronal marker (neurofilament protein, NFP) were undertaken in rats treated with the adrenergic drug, yohimbine. These studies revealed a predominantly neuronal localization of Fos protein in the cerebral cortex. The latter results indicate that neurons are the postsynaptic noradrenergic target cells in which this immediate early gene is expressed in response to the stimulation of β adrenoceptors. The possible relation of these findings to the glial localization of these receptors is discussed.     

Effects of simultaneous exposure to stress and nicotine on nicotine-induced locomotor activation in adolescent and adult rats

Preclinical studies have shown that repeated stress experiences can result in an increase in the locomotor response to the subsequent administration of drugs of abuse, a phenomenon that has been termed behavioral cross-sensitization. Behavioral sensitization reflects neuroadaptive processes associated with drug addiction and drug-induced psychosis. Although crosssensitization between stress- and drug-induced locomotor activity has been clearly demonstrated in adult rats, few studies have evaluated this phenomenon in adolescent rats. In the present study, we determined if the simultaneous exposure to stress and nicotine was capable of inducing behavioral sensitization to nicotine in adolescent and adult rats. To this end, adolescent (postnatal day (P) 28-37) and adult (P60-67) rats received nicotine (0.4 mg/kg, sc) or saline (0.9% NaCl, sc) and were immediately subjected to restraint stress for 2 h once a day for 7 days. The control group for stress was undisturbed following nicotine or saline injections. Three days after the last exposure to stress and nicotine, rats were challenged with a single dose of nicotine (0.4 mg/kg, sc) or saline and nicotine-induced locomotion was then recorded for 30 min. In adolescent rats, nicotine caused behavioral sensitization only in animals that were simultaneously exposed to stress, while in adult rats nicotine promoted sensitization independently of stress exposure. These findings demonstrate that adolescent rats are more vulnerable to the effects of stress on behavioral sensitization to nicotine than adult rats.     

尼古丁处理对大鼠脑内多巴胺转运体和酪氨酸羟化酶的影响

目的 观察尼古丁处理大鼠脑内多巴胺转运体(DAT)和酪氨酸羟化酶(TH)的表达变化,探讨尼古丁处理对大鼠脑内多巴胺(DA)能神经体系的影响. 方法 选用雄性Wistar大鼠按每日 0.4 mg/kg 腹腔注射尼古丁 7d;利用免疫组织化学和免疫印迹法,检测尼古丁处理大鼠有关脑区DAT和TH的表达改变. 结果 与对照组相比:1. 免疫组织化学显示,尼古丁处理组大鼠伏核(NACC)和腹则被盖区(VTA)的DAT灰度值降低了12.43 %和12.85 %;TH的灰度值则降低了11.87 %和10.09 %.2. 免疫印迹法显示,尼古丁处理组大鼠尾壳核(CPu)-NACC、黑质(SN)-VTA的DAT与β-肌动蛋白(β-actin)条带相对吸光度比值增加了75.68 %和117.14 %;而TH的比值则分别增加了66.32 %和60.31 %. 结论 尼古丁处理增加大鼠脑内DAT和TH的表达,这可能与尼古丁的成瘾机制有关.     

Nicotine-induced conditioned place preference in adolescent and adult rats

About 1 million American adolescents start smoking every year. Adolescents may be unusually sensitive to certain consequences of nicotine, demonstrating, for instance, significantly higher rates of dependence than adults at the same level of nicotine use. To explore whether adolescents may be more sensitive to rewarding properties of nicotine than adults, the present study used an animal model to assess the rewarding effects of a low nicotine dose (0.6 mg/kg) in a conditioned place preference (CPP) paradigm. Locomotor activity during conditioning and testing was also evaluated. Nicotine was observed to induce place preference conditioning in adolescent Sprague-Dawley rats, whereas the training dose of 0.6 mg/kg failed to produce convincing place preference in their adult counterparts. Age differences were also apparent in terms of nicotine influences on motor activity, with adults being more sensitive to nicotine-suppressant effects and only adolescents showing an emergence of nicotine-stimulatory effects upon repeated exposures. An increased predisposition to stimulatory nicotine effects during adolescence may contribute to age-specific rewarding properties of the drug as revealed using the CPP paradigm in this experiment. Increased sensitivity to stimulatory and rewarding effects during adolescence could potentially contribute to the high rate of nicotine use and dependence among human adolescents.     

Acute administration of ethanol suppresses pentylenetetrazole-induced c-fos expression in rat brain

The effect of acute ethanol administration on pentylenetetrazole-induced c-fos expression in rat brain was studied. Pentylenetetrazole induced the rapid and transient expression of c-fos mRNA in rat brain. Maximal induction at a dose of 30 mg/kg was detected within 30 min and persisted for 60 min. Thereafter c-fos gene expression decreased to control levels by 180 min. No increase in c-fos mRNA was evident at doses of pentylenetetrazole 20 mg/kg, whereas maximal elevation was seen at 30 or 40 mg/kg. This action was inhibited by acute ethanol treatment (blood alcohol level > 100 mg/dl). Acute ethanol treatment alone had no effect on c-fos gene expression.     

The electrophysiological effects of nicotine in the rat cerebellum: evidence for direct postsynaptic actions

The agonistic actions of nicotine in the cerebellum were dependent on the type of cerebellar neuron studied. Purkinje cells were inhibited and cerebellar interneurons were excited by pressure-ejected nicotine. The simultaneous iontophoresis of Mg²⁺ failed to block nicotine agonistic actions on either cell type. Since Mg²⁺ reduces presynaptic release of neurotransmitters, our findings suggest that the pharmacological actions of nicotine on cerebellar neurons are due to direct postsynaptic mechanisms.     

Differential expression of arc mRNA and other plasticity-related genes induced by nicotine in adolescent rat forebrain

Relatively little attention has been focused on mechanisms related to neural plasticity and drug abuse in adolescence, compared with abundant research using adult animal models. As smoking is typically initiated in adolescence, an important question to address is whether the adolescent brain responds differently to nicotine compared with the adult. To investigate this question, we examined the expression of a number of early response genes (arc, c-fos and NGFI-B) that have been implicated in synaptic plasticity and addiction, following acute nicotine in adolescent and adult rats. Baseline expression of arc and c-fos was higher in adolescent brains compared with adults. Following acute nicotine treatment (0.1, 0.4mg/kg), we found a marked induction of arc mRNA in the prefrontal cortex of nicotine-treated adolescents compared with a less pronounced increase of arc in the adult. c-fos and NGFI-B were also upregulated by nicotine, but not in an age-related manner. In contrast, nicotine induced less arc, c-fos, and NGFI-B expression in the somatosensory cortex of adolescents compared with adults. A fourth gene, quinoid dihydropteridine reductase was expressed at lower levels in white matter of the adolescent forebrain compared with the adult, but was not affected by nicotine. These results suggest that in adolescence, the activity of specific early response genes is higher in brain regions critical for emotional regulation and decision-making. Further, nicotine affects key plasticity molecules in these areas in a manner different from the adult. Thus, adolescence may represent a neurobiologically vulnerable period with regard to nicotine exposure.     

Acute nicotine activates c-fos and activity-regulated cytoskeletal associated protein mRNA expression in limbic brain areas involved in the central stress-response in rat pups during a period of hypo-responsiveness to stress

In adult rats, acute nicotine, the major psychoactive ingredient in tobacco smoke, stimulates the hypothalamic-pituitary-adrenal axis (HPA), resulting in activation of brain areas involved in stress and anxiety-linked behavior. However, in rat pups the first two postnatal weeks are characterized by hypo-responsiveness to stress, also called the 'stress non-responsive period' (SNRP). Therefore, we wanted to address the question if acute nicotine stimulates areas involved in the stress response during SNRP. To determine neuronal activation, the expression of the immediate-early genes c-fos and activity-regulated cytoskeletal associated protein (Arc) was studied in the central nucleus of the amygdala (CeA), bed nucleus stria terminalis (BST) and paraventricular hypothalamic nucleus (PVN), which are areas involved in the neuroendocrine and central stress response. Rat pups received nicotine tartrate (2 mg/kg) or saline by i.p. injection at postnatal days (P) 5, 7 and 10 and their brains were removed after 30 min. We used semi-quantitative radioactive in situ hybridization with gene specific antisense cRNA probes in coronal sections. In control pups, c-fos expression was low in most brain regions, but robust Arc hybridization was found in several areas including cingulate cortex, hippocampus and caudate. Acute nicotine resulted in significant induction of c-fos expression in the PVN and CeA at P5, P7 and P10, and in the BST at P7 and P10. Acute nicotine significantly induced expression of Arc in CeA at P5, P7 and P10, and in the BST at P10. In conclusion, acute nicotine age dependently activated different brain areas of the HPA axis during the SNRP. After P7, the response was more pronounced and included the BST, suggesting differential maturation of the HPA axis in response to nicotine.     

Depression by nicotine of pain-related nociceptive activity in the rat thalamus and spinal cord

Summary To assess the possible role of nicotinergic control in nociception and pain, experiments were carried out on rats under urethane anesthesia in which nociceptive activity was elicited by electrical stimulation of afferent C fibers in the sural nerve and recorded from single neurones in the thalamus and from ascending axons in the spinal cord. Intravenous administration of nicotine (0.01–0.5 mg/kg) depressed the nociceptive activity evoked in the thalamus and the spinal cord in a dose-dependent way. The maximum depression in thalamus and spinal cord was 40% of control activity and obtained at a dose of 0.025 mg/kg. Likewise, local administration of nicotine to the spinal cord by intrathecal injection (5, 10, and 30 g) reduced the nociceptive activity evoked in neurones of the thalamus and in ascending axons of the spinal cord, the maximum of the depression being 40% of control activity. The depressant effect of nicotine (0.05 mg/kg) was reduced by mecamylamine (1 mg/kg) but not by atropine (0.5 mg/kg). It is concluded that the antinociceptive effect of nicotine is due to a specific action of the alcaloid at the spinal level.     

严重烫伤后脑内ZO-1mRNA表达变化与血脑屏障功能的关系

目的:探讨脑内ZO-1mRNA的表达水平在严重烫伤过程中的动态变化及其与血脑屏障功能的关系。方法:建立30%TBSAⅢ度烫伤模型,Sprague-Dawley大鼠随机分为正常对照组、烫伤组,其中烫伤组又分为烫伤后1、3、6、12、24h等5组,应用半定量逆转录-聚合酶链式反应(RT-PCR)检测ZO-1mRNA基因的表达水平,用化学法测定血脑屏障对伊文氏蓝的通透性,并分析二者的变化趋势。结果:严重烫伤后脑内ZO-1mRNA的表达迅速降低,其中以烫伤后3h降低最为显著。严重烫伤后脑组织内伊文氏蓝含量增高,其中以6h最为明显,大脑、小脑分别为(20±0.58)μg/g、(31.33±1.47)μg/g。结论:严重烫伤后的大脑内ZO-1mRNA的表达下降(P<0.01),伊文氏蓝的含量升高,ZO-1mRNA表达水平降低可能标志着血脑屏障的破坏。     

Increased expression of VMAT2 in dopaminergic neurons during nicotine withdrawal

Evidence suggests that the vesicular monoamine transporter-2 (VMAT2) is regulated in striatum and dopamine (DA) may play a role in its regulation. DA is an important mediator of the behavioral actions of nicotine, and dopaminergic neurotransmission is altered following nicotine administration. We investigated the effect of nicotine withdrawal on the expression of VMAT2 in the midbrain DA neurons in animals dependent to nicotine. Mice were injected with nicotine free base 2 mg/kg, sc, four times daily for 14 days and killed 12–72 h after drug discontinuation. VMAT2 protein was increased in the striatum of nicotine-treated mice in a time-dependent fashion at all times studied. Furthermore, in situ hybridization studies demonstrated that VMAT2 mRNA was elevated in the substantia nigra pars compacta and ventral tegmental area, indicating enhanced gene expression and subsequent protein synthesis. Tissue DA content and synthesis were unaltered in the striatum of nicotine-treated mice at the times studied. However, basal DA release was decreased at 12 and 24 h after nicotine discontinuation which coincided with the elevated levels of VMAT2 protein. VMAT2 up-regulation might be a compensatory mechanism to restore and maintain synaptic transmission in dopaminergic midbrain neurons during nicotine withdrawal.     

Regional and temporal expression of sodium channel messenger RNAs in the rat brain during development

Summary The distribution of mRNA expression for three types of voltage gated neuronal sodium-channels was studied in the rat brain at different developmental stages (embryonal day E18, postnatal day P5 and adult). With the in-situ hybridization technique, using synthetic DNA-oligomer probes, pronounced regional and temporal variations in the expression levels of the different channel subtypes could be detected. In comparison with types I and III, sodium channel II mRNA was the most abundant subtype at all developmental stages. Maximal expression of sodium channel II mRNA was seen at P5 in virtually all parts of the grey matter, except for the cerebellum. In adult rat brain in contrast, sodium channel II mRNA levels were maximal in the granular layer of the cerebellum, whereas in all other regions expression had decreased to roughly 50% of postnatal levels. Na channel I expression was virtually absent at E18 and showed highest levels at P5, with maxima in the caudate nucleus and hippocampus. In the adult brain, expression of Na-channel I was nearly absent in the neocortex, but well detectable in the cerebellum and, at lower levels in the striatum and thalamus. Sodium channel III was mainly expressed at the embryonal stage and showed a decrease to very low levels with little regional preferences in the adult.Supported by Deutsche Forschungsgemeinschaft grant no.: Cr 30/16     

Sleep deprivation and c-fos expression in the rat brain

SUMMARY  This study examined the effects of sleep deprivation on the expression of the immediate early gene c-fos in the brain with both in situ hybridization and immunocytochemistry. Rats were manually sleep-derived for 3 h, 6 h, 12 h, and 24 h starting at light onset (08.00 hours), and for 12 h starting at dark onset (20.00 hours). c-Fos expression was found to be higher in sleep-deprived rats with respect to control animals in several brain areas. The increase was evident both in terms of c-fos mRNA and Fos protein, although with a different time course. Among the areas that showed a consistent induction of c-fos were many cortical regions, the medial preoptic area and the posterior hypothalamic area, some thalamic nuclei, and several nuclei of the dorsal pontine tegmentum. The pattern of c-fos expression after sleep deprivation was very similar to that observed after comparable periods of spontaneous wakefulness (Pompeiano et al. 1994). In general, the increase in c-fos expression was not simply proportional to the amount of previous wakefulness. In many areas, the highest levels of c-fos were seen after 3 h of sleep deprivation. These observations are discussed with respect to the homeostatic regulation of sleep and to the functional consequences of wakefulness in specific brain areas.     

尼古丁对中性粒细胞活化及细胞间粘附分子基因表达的影响

目的:观察尼古丁对中性粒细胞(PMNs)的活化,PMNs与内皮细胞的粘附及内皮细胞表达ICAM-1mRNA,有助于阐明尼古丁在慢性阻塞性肺疾患(COPD)炎症发病中的作用。方法:测定β-葡萄糖醛酸苷酶及溶菌酶活性,以反映PMNs的活化;培养人脐静脉内皮细胞,观察PMNs与内皮细胞的粘附;制备探针,提取总RNA,Northern杂交测细胞间粘附分子-1(ICAM-1)mRNA。结果:尼古丁可活化PMNs,增加PMNs－内皮细胞粘附;增强ICAM-1mRNA表达,764-3可明显抑制尼古丁的上述作用。结论:尼古丁通过活化PMNs,促进PMNs－内皮细胞粘附,在COPD慢性炎症发病中起重要作用。而这种粘附作用的增加与粘附分子表达增强有关;抑制尼古丁的上述作用可能是764-3抗炎作用的部分机理。     

Acute intermittent nicotine treatment induces fibroblast growth factor-2 in the subventricular zone of the adult rat brain and enhances neuronal precursor cell proliferation

Over the past years, evidence has accumulated that stem cells are present in the adult brain, and generate neurons and/or glia from two active germinal zones: the subventricular zone (SVZ) of the lateral ventricles and the subgranular zone (SGZ) of the dentate gyrus of the hippocampus. This study shows that acute intermittent nicotine treatment significantly enhances neuronal precursor cell proliferation in the SVZ of adult rat brain, but not in the SGZ of the hippocampus, and pre-treatment with mecamylamine, a nonselective nAChR antagonist, blocks the enhanced precursor proliferation by nicotine. This effect is supported by up-regulation of fibroblast growth factor-2 (FGF-2) mRNA in the SVZ and the expression of its receptor FGFR-1 in cells of SVZ showing precursor cells profile. It is also demonstrated that the nicotine effect on neuronal precursor proliferation is mediated by FGF-2 via fibroblast growth factor receptor 1 (FGFR-1) activation by showing that i.c.v. pre-treatment with anti-FGF-2 antibodies or with FGFR-1 inhibitor 3-[(3-(2-carboxyethyl)-4-methylpyrrol-2-yl)methylene]-2-indolinone (SU5402) blocks nicotine-induced precursor cell proliferation. This nicotine enhancement of neuronal precursor cell proliferation was not accompanied by an increase in the number of apoptotic cells. Taken together the present findings revealed the existence in the SVZ of the adult rat brain of a trophic mechanism mediated by FGF-2 and its receptor and regulated by nAchR activation. This possibility of in vivo regulation of neurogenesis in the adult brain by exogenous factors may aid to develop treatments stimulating neurogenesis with potential therapeutic implications.     

Effects of nicotine on rat sternohyoid muscle contractile properties

Obstructive sleep apnoea (OSA) is a major clinical disorder characterised by recurring episodes of pharyngeal collapse during sleep. At present, there remains no satisfactory treatment for OSA. Pharmacological therapies as a potential treatment for the disorder are an attractive option and include agents that increase the contractility of the pharyngeal muscles. The aim of the present study was to examine the effects of nicotine on upper airway muscle contractile properties. In vitro isometric contractile properties were determined using strips of rat sternohyoid muscle in physiological salt solution containing nicotine (0-100 microg/ml) at 25 degrees C. Isometric twitch and tetanic tension, contraction time, half-relaxation time and tension-frequency relationship were determined by electrical field stimulation with platinum electrodes. Fatigue was induced by stimulation at 40 Hz with 300 ms trains at a frequency of 0.5 Hz for 5 min. Nicotine at a concentration of 1 microg/ml was associated with a significant increase in sternohyoid muscle specific tension compared to control data. Dose-dependent increases in contractile tension were not observed. Nicotine had effects on tension-frequency relationship and endurance properties of the sternohyoid muscle at some but not all doses. A leftward shift in the tension-frequency relationship was observed at low stimulus frequencies (20-30 Hz) for nicotine at a concentration of 1 and 5 microg/ml and a significant increase in fatigue resistance was observed with nicotine at a concentration of 10 microg/ml. As fatigue of the upper airway muscles has been implicated in obstructive airway conditions, a pharmacological agent that improves muscle endurance may prove useful as a potential treatment for such disorders. Therefore, further studies of the effects of nicotinic agonists on upper airway function are warranted.