The role of nicotinic acetylcholine receptors

Epilepsy, Neurophysiology and Neurogenetics Unit, Department of Child Neurology and Psychiatry, IRCCS Stella Maris Foundation, Pisa, Italy.
Biochemical Pharmacology (Impact Factor: 5.01). 11/2007; 74(8):1308-14. DOI: 10.1016/j.bcp.2007.06.030
Source: PubMed


The role of neuronal acetylcholine receptors (nAChRs) in epilepsy has been clearly established by the finding of mutations in a subset of genes coding for subunits of the nAChRs in a form of sleep-related epilepsy with familial occurrence in about 30% of probands and dominant inheritance, named autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). Sporadic and familial forms have similar clinical and EEG features. Seizures begin in middle childhood as clusters of sleep-related attacks with prominent motor activity, and sustained dystonic posturing. In addition to nocturnal seizures, psychosis or schizophrenia, behavioral disorders, memory deficits and mental retardation were described in some individuals. Although over hundred families are on record, only a minority of them have been linked to mutations in the genes coding for the alpha4, alpha2 and beta2 (CHRNA4, CHRNA2, and CHRNB2) subunits of the nAChRs, indicating that ADNFLE is genetically heterogeneous despite a relatively homogeneous clinical picture. Functional characterization of some mutations suggests that gain of the receptor function might be the basis for epileptogenesis. In vitro and in vivo studies have shown high density of nAChRs in the thalamus, over activated brainstem ascending cholinergic pathway and enhanced GABAergic function, reinforcing the hypothesis that cortico-subcortical networks, regulating arousal from sleep, play a central role in seizure precipitation in ADNFLE.

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    • "The a7 and a4b2 nAChRs are found at pre-and postsynaptic sites, as well as non-synaptic sites in various regions of the brain [27] [28] [29] [30] [31] [32] [33]. Due to the widespread distribution of nAChRs in the central nervous system, it is not surprising that they are involved in the pathophysiology of many neurological diseases and conditions [1] [3] [34], including (but not limited to) nicotine addiction [35] [36] [37], Alzheimer's disease [33] [38] [39], human epilepsy syndrome [40] [41] [42] [43], schizophrenia [44] [45] [46] and autism [47] [48] [49]. Experimental evidence also suggests that nAChRs are involved in cognitive processes like attention [50– 53] and learning and memory [54] [55], in the central processing of pain [56] [57] [58] [59] [60] [61] [62] [63] [64] [65], and in psychological behaviors such as anxiety [54,66–69] and depression [68] [70] [71]. "
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    ABSTRACT: Nicotinic acetylcholine receptors (nAChRs) are ligand-gated cation-conducting transmembrane channels from the cys-loop receptor superfamily. The neuronal subtypes of these receptors (e.g. the α7 and α4β2 subtypes) are involved in neurobehavioral processes such as anxiety, the central processing of pain, food intake, nicotine seeking behavior, and a number of cognitive functions like learning and memory. Neuronal nAChR dysfunction is involved in the pathophysiology of many neurological disorders, and behavioral studies in animals are useful models to assess the effects of compounds that act on these receptors. Allosteric modulators are ligands that bind to the receptors at sites other than the orthosteric site where acetylcholine, the endogenous agonist for the nAChRs, binds. While conventional ligands for the neuronal nAChRs have been studied for their behavioral effects in animals, allosteric modulators for these receptors have only recently gained attention, and research on their behavioral effects is growing rapidly. Here we will discuss the behavioral effects of allosteric modulators of the neuronal nAChRs.
    Biochemical pharmacology 05/2013; 86(8). DOI:10.1016/j.bcp.2013.05.018 · 5.01 Impact Factor
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    • "The pathogenetic role of nicotine has yet to be clarified in NFLE [4] [15]. Experimental data on animals showed that nicotine injection induced a pathological locomotor activity and an escape reaction by "
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    ABSTRACT: The beneficial effect of nicotine has been reported in autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) patients, but not tested in sporadic cases. Recently, a nicotine defect in the arousal pathway has been hypothesized even in sporadic NFLE patients and their relatives. This case-control family study was designed to test whether NFLE subjects were more likely to use tobacco than controls, as an indirect marker of cholinergic arousal system dysregulation. At least four relatives were included for each NFLE proband and control. Each subject was questioned about tobacco habits; 434 individuals were recruited. Moreover, we compared NFLE patients with age- and sex-matched controls to determine whether they are more likely to use tobacco. We found a slightly higher trend of tobacco use in NFLE probands compared to that in control subjects; we did not find any significant difference in the distribution of tobacco use among NFLE group compared to that in the control group.
    Epilepsy & Behavior 12/2012; 26(1). DOI:10.1016/j.yebeh.2012.10.014 · 2.26 Impact Factor
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    • "A. Zerem et al. desensitize nAChRs, and in typical smokers, virtually all nAChRs are desensitized, especially a4b2 receptors (Bertrand et al., 2002; Marini & Guerrini, 2007; Hoda et al., 2008). Carbamazepine has a few modes of action in epilepsy, one of which is interaction with nAChR by entering the ionic pore and blocking it. "
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    ABSTRACT: We report resolution of an epileptic encephalopathy by administration of transdermal nicotine patches in an adolescent with severe nonlesional refractory frontal lobe epilepsy. The 18.5-year-old female patient had refractory epilepsy from the age of 11. Recurrent electroencephalography (EEG) recordings showed mostly generalized activity, albeit with right frontal predominance. Almost all antiepileptic medications failed to provide benefit. She developed an encephalopathic state with cognitive decline. The nonlesional frontal lobe epilepsy and a family history of a cousin with nocturnal epilepsy with frontal origin suggested genetic etiology. Transdermal nicotine patches brought complete resolution of the seizures, normalization of the EEG, and a significant improvement in her thinking process and speech organization. Sequencing of the CHRNB2 and CHRNA4 genes did not detect a mutation. Transdermal nicotine patches should be considered in severe pharmacoresistant frontal lobe epilepsy.
    Epilepsia 10/2012; 54(1). DOI:10.1111/j.1528-1167.2012.03715.x · 4.57 Impact Factor
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