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Brain : a Journal of Neurology Jul 2018Cholinergic synapses are ubiquitous in the human central nervous system. Their high density in the thalamus, striatum, limbic system, and neocortex suggest that... (Review)
Review
Cholinergic synapses are ubiquitous in the human central nervous system. Their high density in the thalamus, striatum, limbic system, and neocortex suggest that cholinergic transmission is likely to be critically important for memory, learning, attention and other higher brain functions. Several lines of research suggest additional roles for cholinergic systems in overall brain homeostasis and plasticity. As such, the brain's cholinergic system occupies a central role in ongoing research related to normal cognition and age-related cognitive decline, including dementias such as Alzheimer's disease. The cholinergic hypothesis of Alzheimer's disease centres on the progressive loss of limbic and neocortical cholinergic innervation. Neurofibrillary degeneration in the basal forebrain is believed to be the primary cause for the dysfunction and death of forebrain cholinergic neurons, giving rise to a widespread presynaptic cholinergic denervation. Cholinesterase inhibitors increase the availability of acetylcholine at synapses in the brain and are one of the few drug therapies that have been proven clinically useful in the treatment of Alzheimer's disease dementia, thus validating the cholinergic system as an important therapeutic target in the disease. This review includes an overview of the role of the cholinergic system in cognition and an updated understanding of how cholinergic deficits in Alzheimer's disease interact with other aspects of disease pathophysiology, including plaques composed of amyloid-β proteins. This review also documents the benefits of cholinergic therapies at various stages of Alzheimer's disease and during long-term follow-up as visualized in novel imaging studies. The weight of the evidence supports the continued value of cholinergic drugs as a standard, cornerstone pharmacological approach in Alzheimer's disease, particularly as we look ahead to future combination therapies that address symptoms as well as disease progression.
Topics: Alzheimer Disease; Amyloid beta-Peptides; Cholinergic Agents; Cholinergic Neurons; Cholinesterase Inhibitors; Cognition; Cognition Disorders; Humans; Neurofibrillary Tangles
PubMed: 29850777
DOI: 10.1093/brain/awy132 -
Current Neuropharmacology 2016Acetylcholine (ACh) has a crucial role in the peripheral and central nervous systems. The enzyme choline acetyltransferase (ChAT) is responsible for synthesizing ACh... (Review)
Review
Acetylcholine (ACh) has a crucial role in the peripheral and central nervous systems. The enzyme choline acetyltransferase (ChAT) is responsible for synthesizing ACh from acetyl-CoA and choline in the cytoplasm and the vesicular acetylcholine transporter (VAChT) uptakes the neurotransmitter into synaptic vesicles. Following depolarization, ACh undergoes exocytosis reaching the synaptic cleft, where it can bind its receptors, including muscarinic and nicotinic receptors. ACh present at the synaptic cleft is promptly hydrolyzed by the enzyme acetylcholinesterase (AChE), forming acetate and choline, which is recycled into the presynaptic nerve terminal by the high-affinity choline transporter (CHT1). Cholinergic neurons located in the basal forebrain, including the neurons that form the nucleus basalis of Meynert, are severely lost in Alzheimer's disease (AD). AD is the most ordinary cause of dementia affecting 25 million people worldwide. The hallmarks of the disease are the accumulation of neurofibrillary tangles and amyloid plaques. However, there is no real correlation between levels of cortical plaques and AD-related cognitive impairment. Nevertheless, synaptic loss is the principal correlate of disease progression and loss of cholinergic neurons contributes to memory and attention deficits. Thus, drugs that act on the cholinergic system represent a promising option to treat AD patients.
Topics: Acetylcholine; Alzheimer Disease; Animals; Cholinergic Agents; Cholinergic Neurons; Cholinesterase Inhibitors; Drug Delivery Systems; Humans; Receptors, Cholinergic
PubMed: 26813123
DOI: 10.2174/1570159x13666150716165726 -
Neuron Nov 2022Cholinergic neurons in the medial septum (MS) constitute a major source of cholinergic input to the forebrain and modulate diverse functions, including sensory...
Cholinergic neurons in the medial septum (MS) constitute a major source of cholinergic input to the forebrain and modulate diverse functions, including sensory processing, memory, and attention. Most studies to date have treated cholinergic neurons as a single population; as such, the organizational principles underling their functional diversity remain unknown. Here, we identified two subsets (D28K versus D28K) of cholinergic neurons that are topographically segregated in mice, Macaca fascicularis, and humans. These cholinergic subpopulations possess unique electrophysiological signatures, express mutually exclusive marker genes (kcnh1 and aifm3 versus cacna1h and gga3), and make differential connections with physiologically distinct neuronal classes in the hippocampus to form two structurally defined and functionally distinct circuits. Gain- and loss-of-function studies on these circuits revealed their differential roles in modulation of anxiety-like behavior and spatial memory. These results provide a molecular and circuitry-based theory for how cholinergic neurons contribute to their diverse behavioral functions.
Topics: Humans; Mice; Animals; Cholinergic Neurons; Cholinergic Agents; Prosencephalon; Hippocampus
PubMed: 36130594
DOI: 10.1016/j.neuron.2022.08.025 -
Nature Communications Apr 2023Nucleus- and cell-specific interrogation of individual basal forebrain (BF) cholinergic circuits is crucial for refining targets to treat comorbid chronic pain-like and...
Nucleus- and cell-specific interrogation of individual basal forebrain (BF) cholinergic circuits is crucial for refining targets to treat comorbid chronic pain-like and depression-like behaviour. As the ventral pallidum (VP) in the BF regulates pain perception and emotions, we aim to address the role of VP-derived cholinergic circuits in hyperalgesia and depression-like behaviour in chronic pain mouse model. In male mice, VP cholinergic neurons innervate local non-cholinergic neurons and modulate downstream basolateral amygdala (BLA) neurons through nicotinic acetylcholine receptors. These cholinergic circuits are mobilized by pain-like stimuli and become hyperactive during persistent pain. Acute stimulation of VP cholinergic neurons and the VP-BLA cholinergic projection reduces pain threshold in naïve mice whereas inhibition of the circuits elevated pain threshold in pain-like states. Multi-day repetitive modulation of the VP-BLA cholinergic pathway regulates depression-like behaviour in persistent pain. Therefore, VP-derived cholinergic circuits are implicated in comorbid hyperalgesia and depression-like behaviour in chronic pain mouse model.
Topics: Mice; Male; Animals; Basal Forebrain; Depression; Chronic Pain; Hyperalgesia; Cholinergic Neurons
PubMed: 37069246
DOI: 10.1038/s41467-023-37968-x -
Cell Dec 2023Conscious perception is greatly diminished during sleep, but the underlying circuit mechanism is poorly understood. We show that cortical ignition-a brain process shown...
Conscious perception is greatly diminished during sleep, but the underlying circuit mechanism is poorly understood. We show that cortical ignition-a brain process shown to be associated with conscious awareness in humans and non-human primates-is strongly suppressed during non-rapid-eye-movement (NREM) sleep in mice due to reduced cholinergic modulation and rapid inhibition of cortical responses. Brain-wide functional ultrasound imaging and cell-type-specific calcium imaging combined with optogenetics showed that activity propagation from visual to frontal cortex is markedly reduced during NREM sleep due to strong inhibition of frontal pyramidal neurons. Chemogenetic activation and inactivation of basal forebrain cholinergic neurons powerfully increased and decreased visual-to-frontal activity propagation, respectively. Furthermore, although multiple subtypes of dendrite-targeting GABAergic interneurons in the frontal cortex are more active during wakefulness, soma-targeting parvalbumin-expressing interneurons are more active during sleep. Chemogenetic manipulation of parvalbumin interneurons showed that sleep/wake-dependent cortical ignition is strongly modulated by perisomatic inhibition of pyramidal neurons.
Topics: Animals; Mice; Cholinergic Neurons; Electroencephalography; Frontal Lobe; Parvalbumins; Sleep; Wakefulness
PubMed: 38070510
DOI: 10.1016/j.cell.2023.11.012 -
Neuron Jul 2021The vagus nerve innervates many organs, and most, if not all, of its motor fibers are cholinergic. However, no one knows its organizing principles-whether or not there...
The vagus nerve innervates many organs, and most, if not all, of its motor fibers are cholinergic. However, no one knows its organizing principles-whether or not there are dedicated neurons with restricted targets that act as "labeled lines" to perform certain functions, including two opposing ones (gastric contraction versus relaxation). By performing unbiased transcriptional profiling of DMV cholinergic neurons, we discovered seven molecularly distinct subtypes of motor neurons. Then, by using subtype-specific Cre driver mice, we show that two of these subtypes exclusively innervate the glandular domain of the stomach where, remarkably, they contact different enteric neurons releasing functionally opposing neurotransmitters (acetylcholine versus nitric oxide). Thus, the vagus motor nerve communicates via genetically defined labeled lines to control functionally unique enteric neurons within discrete subregions of the gastrointestinal tract. This discovery reveals that the parasympathetic nervous system utilizes a striking division of labor to control autonomic function.
Topics: Animals; Brain; Cholinergic Neurons; Enteric Nervous System; Gastric Mucosa; Gene Expression Profiling; Male; Mice, Inbred C57BL; Mice, Transgenic; Motor Neurons; Neural Pathways; Stomach; Vagus Nerve; Mice
PubMed: 34077742
DOI: 10.1016/j.neuron.2021.05.004 -
The European Journal of Neuroscience Mar 2019The purpose of this review is to bridge the gap between earlier literature on striatal cholinergic interneurons and mechanisms of microcircuit interaction demonstrated... (Review)
Review
The purpose of this review is to bridge the gap between earlier literature on striatal cholinergic interneurons and mechanisms of microcircuit interaction demonstrated with the use of newly available tools. It is well known that the main source of the high level of acetylcholine in the striatum, compared to other brain regions, is the cholinergic interneurons. These interneurons provide an extensive local innervation that suggests they may be a key modulator of striatal microcircuits. Supporting this idea requires the consideration of functional properties of these interneurons, their influence on medium spiny neurons, other interneurons, and interactions with other synaptic regulators. Here, we underline the effects of intrastriatal and extrastriatal afferents onto cholinergic interneurons and discuss the activation of pre- and postsynaptic muscarinic and nicotinic receptors that participate in the modulation of intrastriatal neuronal interactions. We further address recent findings about corelease of other transmitters in cholinergic interneurons and actions of these interneurons in striosome and matrix compartments. In addition, we summarize recent evidence on acetylcholine-mediated striatal synaptic plasticity and propose roles for cholinergic interneurons in normal striatal physiology. A short examination of their role in neurological disorders such as Parkinson's, Huntington's, and Tourette's pathologies and dystonia is also included.
Topics: Animals; Basal Ganglia Diseases; Cholinergic Neurons; Corpus Striatum; Humans; Interneurons; Nerve Net; Neuronal Plasticity
PubMed: 29797362
DOI: 10.1111/ejn.13949 -
Developmental Biology Jan 2017Striatal cholinergic interneurons and basal forebrain cholinergic projection neurons, which together comprise the forebrain cholinergic system, regulate attention,... (Review)
Review
Striatal cholinergic interneurons and basal forebrain cholinergic projection neurons, which together comprise the forebrain cholinergic system, regulate attention, memory, reward pathways, and motor activity through the neuromodulation of multiple brain circuits. The importance of these neurons in the etiology of neurocognitive disorders has been well documented, but our understanding of their specification during embryogenesis is still incomplete. All forebrain cholinergic projection neurons and interneurons appear to share a common developmental origin in the embryonic ventral telencephalon, a region that also gives rise to GABAergic projection neurons and interneurons. Significant progress has been made in identifying the key intrinsic and extrinsic factors that promote a cholinergic fate in this precursor population. However, how cholinergic interneurons and projection neurons differentiate from one another during development, as well as how distinct developmental programs contribute to heterogeneity within those two classes, is not yet well understood. In this review we summarize the transcription factors and signaling molecules known to play a role in the specification and early development of striatal and basal forebrain cholinergic neurons. We also discuss the heterogeneity of these populations and its possible developmental origins.
Topics: Animals; Body Patterning; Cholinergic Neurons; Humans; Neural Stem Cells; Prosencephalon; Signal Transduction; Transcription Factors
PubMed: 27847324
DOI: 10.1016/j.ydbio.2016.11.007 -
Neuropharmacology Jan 2016Neurons that produce acetylcholine (ACh) are positioned to broadly influence the brain, with axonal arborizations that extend throughout the cerebral cortex, striatum,... (Review)
Review
Neurons that produce acetylcholine (ACh) are positioned to broadly influence the brain, with axonal arborizations that extend throughout the cerebral cortex, striatum, and hippocampus. While the action of these neurons has typically been attributed entirely to ACh, neurons often release more than one primary neurotransmitter. Here, we review evidence for the cotransmission of the inhibitory neurotransmitter GABA from cholinergic neurons throughout the mammalian central nervous system. Functional cotransmission of ACh and GABA has been reported in the retina and cortex, and anatomical studies suggest that GABA cotransmission is a common feature of nearly all forebrain ACh-producing neurons. Further experiments are necessary to confirm the extent of GABA cotransmission from cholinergic neurons, and the contribution of GABA needs to be considered when studying the functional impact of activity in ACh-producing neurons. This article is part of the Special Issue entitled 'Synaptopathy--from Biology to Therapy'.
Topics: Acetylcholine; Animals; Brain; Cholinergic Neurons; Humans; Mice; Optogenetics; Synaptic Transmission; gamma-Aminobutyric Acid
PubMed: 26220313
DOI: 10.1016/j.neuropharm.2015.07.031 -
Current Neuropharmacology 2019Tacrine is a potent inhibitor of cholinesterases (acetylcholinesterase and butyrylcholinesterase) that shows limiting clinical application by liver toxicity. In spite of... (Review)
Review
Tacrine is a potent inhibitor of cholinesterases (acetylcholinesterase and butyrylcholinesterase) that shows limiting clinical application by liver toxicity. In spite of this, analogues of tacrine are considered as a model inhibitor of cholinesterases in the therapy of Alzheimer's disease. The interest in these compounds is mainly related to a high variety of their structure and biological properties. In the present review, we have described the role of cholinergic transmission and treatment strategies in Alzheimer's disease as well as the synthesis and biological activity of several recently developed classes of multifunctional tacrine analogues and hybrids, which consist of a new paradigm to treat Alzheimer's disease. We have also reported potential of these analogues in the treatment of Alzheimer's diseases in various experimental systems.
Topics: Acetylcholinesterase; Alzheimer Disease; Amyloid beta-Peptides; Animals; Butyrylcholinesterase; Cholinergic Neurons; Cholinesterase Inhibitors; Humans; Tacrine
PubMed: 29651948
DOI: 10.2174/1570159X16666180412091908