Association study of polymorphisms in the alpha 7 nicotinic acetylcholine receptor subunit and catechol-o-methyl transferase genes with sensory gating in first-episode schizophrenia

The purpose of the current study was to explore the association of auditory P50 sensory gating (P50) and prepulse inhibition (PPI) of schizophrenia with polymorphisms in the CHRNA7 and COMT genes. One hundred and fourty patients with schizophrenia participated in this study. They were administered the tests P50 and PPI. Moreover, three single nucleotide polymorphisms (SNPs) (rs2337980, rs1909884 and rs883473) in CHRNA7 and three SNPs (rs4680, rs737865 and rs165599) in COMT were selected to be genotyped by polyacrylamide gel microarray techniques. P50 index showed significant reduction in S2 amplitude between wild-type and mutation groups in the COMT rs4680. S1 amplitude of mutation group in the COMT rs737865 was also lower compared to wild-type group. PPI index revealed a shorter pulse latency of mutation group in the rs4680. The suppression ratio of mutation group was lower in COMT rs165599. Negative findings were shown between comparisons in all the CHRNA7 SNPs. We find that P50 and PPI may be influenced by COMT rs4680 polymorphisms in schizophrenia; more excitingly, we find that P50 might be influenced by COMT rs737865 polymorphisms and PPI may be influenced by COMT rs165599 polymorphisms in schizophrenia, and their mutations are associated with the reduction of the risk of P50 or PPI defects in schizophrenia. Futher studies with a larger number of subjects are needed to verify the present findings.     

Phenotypic characterization of an alpha 4 neuronal nicotinic acetylcholine receptor subunit knock-out mouse.

Neuronal nicotinic acetylcholine receptors (nAChR) are present in high abundance in the nervous system (Decker et al., 1995). There are a large number of subunits expressed in the brain that combine to form multimeric functional receptors. We have generated an alpha(4) nAChR subunit knock-out line and focus on defining the behavioral role of this receptor subunit. Homozygous mutant mice (Mt) are normal in size, fertility, and home-cage behavior. Spontaneous unconditioned motor behavior revealed an ethogram characterized by significant increases in several topographies of exploratory behavior in Mt relative to wild-type mice (Wt) over the course of habituation to a novel environment. Furthermore, the behavior of Mt in the elevated plus-maze assay was consistent with increased basal levels of anxiety. In response to nicotine, Wt exhibited early reductions in a number of behavioral topographies, under both unhabituated and habituated conditions; conversely, heightened levels of behavioral topographies in Mt were reduced by nicotine in the late phase of the unhabituated condition. Ligand autoradiography confirmed the lack of high-affinity binding to radiolabeled nicotine, cytisine, and epibatidine in the thalamus, cortex, and caudate putamen, although binding to a number of discrete nuclei remained. The study confirms the pivotal role played by the alpha(4) nAChR subunit in the modulation of a number of constituents of the normal mouse ethogram and in anxiety as assessed using the plus-maze. Furthermore, the response of Mt to nicotine administration suggests that persistent nicotine binding sites in the habenulo-interpeduncular system are sufficient to modulate motor activity in actively exploring mice.     

烟碱型乙酰胆碱受体基因多态与早发性精神分裂症的关联研究

目的探讨烟碱型乙酰胆碱受体基因多态在早发性精神分裂症发生中的作用。方法采用TaqMan荧光探针基因分型技术对421例早发性精神分裂症患者和598例健康对照者的α3、α4、α7、α5烟碱型乙酰胆碱受体基因(nicotinic acetylcholine receptor subunit gene)即CHRNA3(rs1317286)、CHRNA4(rs1044396)、CHRNA7(rs6494212)及CHRNA5(rs16969968,rs684513)基因多态位点进行基因分型,分析这些位点与早发性精神分裂症的关联及其与发病年龄的关系,并进一步分析基因与基因的交互作用。结果单位点分析显示所有位点的差异比较结果无统计学意义。Kaplan-Meier生存分析显示携带rs1317286G等位基因的患者发病年龄晚于不携带rs1317286G等位基因的患者[发病年龄分别为(15.5±0.33)岁和(15.1±0.14)岁,P=0.010]。CHRNA5基因的两个单核苷酸多态位点(single nucleotide polymorphisms,SNPs)组成的单体型也显示不与早发性精神分裂症关联。进一步的基因交互作用分析显示rs1044396、rs6494212及rs684513联合作用模式可能与精神分裂症相关(P=0.0007)。结论 CHRNA3(rs1317286)位点可能与精神分裂症的发病年龄相关;rs1044396、rs6494212及rs684513基因的联合作用模式可能与早发性精神分裂症有关。     

Two mutations in the nicotinic acetylcholine receptor subunit A4 (CHRNA4) in a family with autosomal dominant sleep‐related hypermotor epilepsy

Sleep‐related hypermotor epilepsy, or nocturnal frontal lobe epilepsy, as it was formerly called, is a focal epilepsy with mostly sleep‐related seizures of hypermotor, tonic or dystonic semiology. Sleep‐related hypermotor epilepsy may be attributed to a monogenetic cause with autosomal dominant inheritance. Mutations are described in different genes, including the genes for three subunits of the nicotinic acetylcholine receptor. We present a family with members over four generations exhibiting sleep‐related hypermotor epilepsy. Genetic testing was available for three members from three generations, and revealed two variants in the alpha‐4 subunit of the nicotinic acetylcholine receptor (one of them being novel) which are likely to be disease‐causing. As these mutations were identified in cis configuration (on the same allele), we do not know whether one of the variants alone or a combination of the two is responsible for the pathogenicity.     

Neurocognitive attention and behavior outcome of school-age children with a history of febrile convulsions: a population study

PURPOSE: A prospective population-based case-control study was performed to ascertain whether febrile convulsion (FC) in early childhood is associated with neurocognitive attention deficits in school age. METHODS: A total of 103 children, confirmed to have FC by age 3 years from a population survey of 4,340 live-birth newborns in Tainan City, Taiwan, was followed up until at least age 6 years. An achievement test, behavioral ratings, and computerized neurocognitive battery assessing various subcomponents of attention were given to 87 FC children (FC group) and 87 randomly selected population-matched control (CC group). RESULTS: Compared with the CC group, the FC group did not have scholastic performance or behavioral outcome disadvantage. Overall FC group performance was distinguished by significantly higher scores in the achievement test and fewer missing errors (p < 0.005) and commission errors (p < 0. 05), less variability in reaction time (p < 0.005), and a nonsignificant trend of impulsivity. Attention performance of the FC and CC groups were comparable. Within the FC group, age at onset, complex FC, recurrence of FC, development of unprovoked seizures, or prior use of phenobarbital had no adverse effects on neurocognitive attention outcome. CONCLUSIONS: This population study suggests that FC in early childhood does not have adverse effects on behavior, scholastic performance, and neurocognitive attention. On the contrary, the FC group demonstrated significantly better control of distractibility and attention at school age.     

Association of the nicotinic receptor beta 2 subunit and febrile seizures

The nicotinic acetylcholine receptors are members of a superfamily of ligand-gated ion channels that mediate fast signal transmission at synapses. Mutations in neuronal nicotinic acetylcholine receptor beta 2 subunit have been associated with autosomal dominant nocturnal frontal lobe epilepsies. A major challenge is to establish whether the monogenic epilepsy gene also contributes to the common epilepsies. Because febrile seizures represent the majority of childhood seizures, and a genetic predisposition, we investigated the possibility that the nicotinic acetylcholine receptor beta 2 subunit might be involved in the etiology of febrile seizures. Children were divided into two groups: those with febrile seizures (group 1; n = 104) and control patients (group 2; n = 83). Polymerase chain reaction was used to identify the G/C and T/C polymorphisms of the nicotinic acetylcholine receptor beta 2 subunit gene, which is mapped on chromosome 1. Genotypes and allelic frequencies for nicotinic acetylcholine receptor beta 2 subunit gene polymorphisms in both groups were compared. The results indicated that genotypes and allelic frequencies in both groups were not significantly different. These data suggest that nicotinic acetylcholine receptor beta 2 subunit polymorphisms are not a useful marker for prediction of the susceptibility to febrile seizures.     

Alpha 4 nicotinic acetylcholine receptor subunit links cholinergic to brainstem monoaminergic neurotransmission

Agonists of nicotinic receptors containing the alpha4-subunit produce antinociception accompanied by several adverse side effects. The purpose of this study was to determine the distribution of the alpha4-subunit of nicotinic acetylcholine receptors (nAChR) in brainstem monoaminergic nuclei that may contribute to these effects using dual labeling immunofluorescence methods. The alpha4-subunit immunoreactivity was enriched in serotonergic (nucleus raphe magnus, pallidus, obscurus, and dorsalis) and noradrenergic (A5, locus coeruleus (LC), A7) areas associated with antinociception, where it was commonly colocalized with serotonin (5-HT) or tyrosine hydroxylase (TH) immunoreactivity. However, it was also noted that alpha4 was present in all other brainstem monoaminergic nuclei examined (adrenergic C1-C3, noradrenergic A1-alpha4, dopamine A9 and A10, nucleus raphe medianus). To determine if alpha4 agonists could impact neural activity in brainstem, monoaminergic nuclei that are associated with antinociception, the expression of c-Fos in response to the systemic administration of epibatidine (2.5, 5, or 10 microg/kg) was examined. Epibatidine produced a robust (2-5-fold) increase in c-Fos expression, which was not dose dependent, in all of these areas examined except the nucleus raphe magnus. These results suggest that the alpha4 subunit is positioned to mediate the effects of acetylcholine widely across many, if not all, monoaminergic neurons in the brainstem. These observations emphasize the potential involvement of noradrenergic, as well as serotonergic mechanisms in epibatidine's analgesic effects, and they also suggest that even selective alpha4 ligand may have widespread effects on brain monoamine neurotransmission.     

精神分裂症伴发2型糖尿病与烟碱型乙酰胆碱受体基因多态性关联研究

目的在中国汉族精神分裂症患者中探讨烟碱型乙酰胆碱受体基因多态性与2型糖尿病共病的关联。方法采用Taq Man荧光探针基因分型技术对346例伴发2型糖尿病的中国汉族精神分裂症患者和360例不伴糖尿病的精神分裂症患者的α3、α4、α7、α5烟碱型乙酰胆碱受体(neuronal nicotinic acetylcholine receptor,n Ach R)基因即CHRNA3(rs1317286)、CHRNA4(rs1044396)、CHRNA7(rs6494212)及CHRNA5(rs16969968、rs684513)多态位点进行基因分型,比较等位基因频率和基因型频率,并进一步进行基因-基因交互作用分析。结果单位点分析显示男性患者rs6494212位点的等位基因分布和基因型分布在两组间差异均有统计学意义(P0.05);rs1317286、rs1044396、rs16969968、rs684513位点的基因型分布和等位基因分布均无明显差异(P均0.05)。CHRNA5基因的两个单核苷酸多态位点(single nucleotide polymorphisms,SNPs)组成的单体型与两组疾病共病关联无统计学意义(P0.05)。进一步基因交互作用分析显示rs131726、rs1044396、rs6494212及rs684513这4个位点的联合作用模式可能与两组疾病共病相关(P=0.002)。结论 CHRNA7(rs6494212)可能是中国汉族男性精神分裂症患者患2型糖尿病的易感基因。rs1317286、rs1044396、rs6494212及rs684513位点的联合作用可能与精神分裂症共病2型糖尿病相关。     

Expression of neuronal nicotinic acetylcholine receptor subunit mRNAs within midbrain dopamine neurons

Many behavioral effects of nicotine result from activation of nigrostriatal and mesolimbic dopaminergic systems. Nicotine regulates dopamine release not only by stimulation of nicotinic acetylcholine receptors (nAChRs) on dopamine cell bodies within the substantia nigra and ventral tegmental area (SN/VTA), but also on presynaptic nAChRs located on striatal terminals. The nAChR subtype(s) present on both cell bodies and terminals is still a matter of controversy. The purpose of this study was to use double-labeling in situ hybridization to identify nAChR subunit mRNAs expressed within dopamine neurons of the SN/VTA, by using a digoxigenin-labeled riboprobe for tyrosine hydroxylase as the dopamine cell marker and (35)S-labeled riboprobes for nAChR subunits. The results reveal a heterogeneous population of nAChR subunit mRNAs within midbrain dopamine neurons. Within the SN, almost all dopamine neurons express alpha2, alpha4, alpha5, alpha6, beta2, and beta3 nAChR mRNAs, with more than half also expressing alpha3 and alpha7 mRNAs. In contrast, less than 10% express beta4 mRNA. Within the VTA, a similar pattern of nAChR subunit mRNA expression is observed except that most subunits are expressed in a slightly lower percentage of dopamine neurons than in the SN. Within the SN, alpha4, beta2, alpha7, and beta4 mRNAs are also expressed in a significant number of nondopaminergic neurons, whereas within the VTA this only occurs for beta4. The heterogeneity in the expression of nAChR subunits within the SN/VTA may indicate the formation of a variety of different nAChR subtypes on cell bodies and terminals of the nigrostriatal and mesolimbic pathways.     

Lower core body temperature and attenuated nicotine-induced hypothermic response in mice lacking the beta4 neuronal nicotinic acetylcholine receptor subunit

Diverse physiological and pathological effects of nicotine, including the alteration of body temperature, are presumably mediated by neuronal nicotinic acetylcholine receptors (nAChR). Previous studies have suggested the involvement of distinct nAChR subunits in nicotine-induced thermoregulation. We studied genetically manipulated knockout mice lacking the alpha7, alpha5 or beta4 subunit genes, in order to assess the effects of subunit deficiency on temperature regulation. Using a telemetry system, core body temperature was monitored continuously prior to and following nicotine administration in mutant mice and in wild-type littermates. Mice lacking in the beta4 nAChR subunit gene had significantly lower baseline core body temperature than all other mouse strains studied. beta4 null mice also demonstrated a reduced nicotine-induced hypothermic response and impaired desensitization following repeat nicotine exposure. These findings suggest the involvement of the beta4 nAChR subunit in both core body temperature homeostasis and nicotine-elicited thermo-alterations in mice.     

Phenobarbital, primidone and sodium valproate in the prophylaxis of febrile convulsions

Of 196 children with febrile convulsions, 6.9 were placed on phenobarbital, 4-5 mg/kg/day b.i.d., and 32 on primidone, 15-20 mg/kg/day b.i.d. The remaining 95 children were given sodium valproate; the dosage was 20-25 mg/kg/day b.i.d. in 38 of them, 20-25 mg/kg/day t.i.d. in 24 of them, and 30 mg/kg/day b.i.d. in 33 patients. Recurrence rate of febrile convulsions during one year were not statistically different among these five groups. However, the dosage regimen of valproate of 20-25 mg/kg/day b.i.d. was relatively inferior to the other regimens of valproate in the prophylactic effect. This may be explained by the facts that when the same daily dosage of sodium valproate was given, the daily fluctuation of plasma levels was greater with the b.i.d.-regimen than with the t.i.d.-regimen, and that when the dosage interval was the same, the minimum plasma level of the day was lower with the smaller daily dosage regimen than with the larger one.     

散发性Alzheimer病与神经型尼古丁胆碱能受体α4α7基因多态性的关联研究

目的探讨散发性Alzheimer病(SAD)与神经型尼古丁胆碱能受体α4亚单位(CHRNA4)基因外显子3、α7亚单位(CHRNA7)基因内含子3、7基因多态性的关联关系。方法用聚合酶链式反应-变性梯度凝胶电泳(PCR-DGGE)和DNA测序技术分析23例SAD患者及30例正常人的CHRNA4基因外显子3基因序列和16例SAD患者及16例正常人CHRNA7基因全部外显子及其两侧的部分内含子基因序列。结果在CHRNA4基因外显子3上发现3个新的多态性位点C104T(2=8,41,P<0.05)、A136G(2=16.21,P<0.05);G169A(2=3.98,P<0.05)。研究结果显示3个多态位点在SAD组与对照组之间存在差异显著性。在CHRNA7基因上发现2个新的多态性位点内含子3G3133418C(2=4.571,P>0.05)、内含子7上117643+GTG三碱基插入突变(2=1.032,P>0.5)统计学结果该2个多态位点在SAD组与对照组之间无差异显著性。结论在CHRNA4基因外显子3上发现的3个新的多态性位点(GeneBank登录号为AY786507AY857199AY857197)与散发性Alzheimer病的发病可能存在相关关系。在CHRNA7基因上发现的2个新的多态性位点(GeneBank登录号为AY641830和AY641831)与散发性Alzheimer病的发病没有显著性的相关关系。因此CHRNA4基因外显子3多态性可能与散发性Alzheimer病发病有关联。     

Effects of nicotine in the dopaminergic system of mice lacking the alpha4 subunit of neuronal nicotinic acetylcholine receptors

The mesostriatal dopaminergic system influences locomotor activity and the reinforcing properties of many drugs of abuse including nicotine. Here we investigate the role of the alpha4 nicotinic acetylcholine receptor (nAChR) subunit in mediating the effects of nicotine in the mesolimbic dopamine system in mice lacking the alpha4 subunit. We show that there are two distinct populations of receptors in the substantia nigra and striatum by using autoradiographic labelling with 125I alpha-conotoxin MII. These receptors are comprised of the alpha4, beta2 and alpha6 nAChR subunits and non-alpha4, beta2, and alpha6 nAChR subunits. Non-alpha4 subunit-containing nAChRs are located on dopaminergic neurons, are functional and respond to nicotine as demonstrated by patch clamp recordings. In vivo microdialysis performed in awake, freely moving mice reveal that mutant mice have basal striatal dopamine levels which are twice as high as those observed in wild-type mice. Despite the fact that both wild-type and alpha4 null mutant mice show a similar increase in dopamine release in response to intrastriatal KCl perfusion, a nicotine-elicited increase in dopamine levels is not observed in mutant mice. Locomotor activity experiments show that there is no difference between wild-type and mutant mice in basal activity in both habituated and non-habituated environments. Interestingly, mutant mice sustain an increase in cocaine-elicited locomotor activity longer than wild-type mice. In addition, mutant mice recover from depressant locomotor activity in response to nicotine at a faster rate. Our results indicate that alpha4-containing nAChRs exert a tonic control on striatal basal dopamine release, which is mediated by a heterogeneous population of nAChRs.     

Unexpected sensitivity of the human alpha7 neuronal nicotinic acetylcholine receptor to aminoglycosides

The wide use of antibiotics and the development of resistance is a major health concern and, despite their relatively severe side effects, aminoglycoside antibiotics are still used in clinics. Effects of seven aminoglycosides were investigated at the human homomeric alpha7 and heteromeric alpha4beta2 neuronal nicotinic acetylcholine receptors. All aminoglycosides tested inhibited the acetylcholine-evoked responses with more pronounced effects at alpha7 than at alpha4beta2. Neomycin displayed higher blockade with a half inhibition in the nanomolar range at low calcium concentration and in the micromolar range in physiological calcium concentration but still exerted blockade below the concentration used in the clinic. These data suggest that some of their side effects may be attributable to their interactions with neuronal nicotinic acetylcholine receptors.     

Association of novel and established polymorphisms in neuronal nicotinic acetylcholine receptors with sporadic Alzheimer's disease

Since the loss of cholinergic neurons in the Alzheimer's disease (AD) brain was first reported, considerable evidence in vivo and in vitro has accumulated in support of the cholinergic hypothesis of AD. The hypothesis is greatly supported by the fact that the most promising drugs against AD are inhibitors of acetylcholinesterase (AChE). To identify the possible mutations and/or polymorphisms of neuronal nicotinic acetylcholine receptor (nAChR) genes related to the pathogenesis of sporadic AD, we have performed mutational analyses of the major neuronal nAChR genes (CHRNA3, 4, 7 and CHRNB2) expressed in central nervous system. Allelic analysis showed association of specific silent or intronic polymorphisms of the CHRNA3 and CHRNA4 genes and AD. Two novel missense point mutations, Ser413Leu in the CHRNA4 gene and Gln397Pro in the CHRNB2 gene, were identified in two different AD cases but were not found in other AD cases and controls. These findings suggested that genetic polymorphisms of the neuronal nAChR genes might be related to the pathogenesis of sporadic AD.