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alpha GPC is a cholinergic supplement that can help increase acetylcholine. Acetylcholine is a neurotransmitter just like serotonin, dopamine, noradrenaline.
Cut and paste fo the function of Acetylcholine -
Acetylcholine has functions both in the peripheral nervous system (PNS) and in the central nervous system (CNS) as a neuromodulator. Its receptors have very high binding constants.
In the peripheral nervous system, acetylcholine activates muscles, and is a major neurotransmitter in the autonomic nervous system.
In the central nervous system, acetylcholine and the associated neurons form a neurotransmitter system, the cholinergic system, which tends to cause anti-excitatory actions.
In the peripheral nervous system[edit]
In the peripheral nervous system, acetylcholine activates muscles, and is a major neurotransmitter in the autonomic nervous system. Acetylcholine binds to acetylcholine receptors on skeletal muscle fibers, it opens ligand-gated sodium channels in the cell membrane. Sodium ions then enter the muscle cell, initiating a sequence of steps that finally produce muscle contraction. Although acetylcholine induces contraction of skeletal muscle, it acts via a different type of receptor (muscarinic) to inhibit contraction of cardiac muscle fibers.
In the autonomic nervous system, acetylcholine is released in the following sites:
Damage to the cholinergic (acetylcholine-producing) system in the brain has been shown to be plausibly associated with the memory deficits associated with Alzheimer's disease.[4] ACh has also been shown to promote REM sleep.[5]
Pathways[edit]
There are three ACh pathways in the CNS.[citation needed]
Acetylcholine is a polyatomic cation. It and the associated neurons form a neurotransmitter system, the cholinergic system from the brainstem and basal forebrain that projects axons to many areas of the brain. In the brainstem it originates from the Pedunculopontine nucleus and laterodorsal tegmental nucleus collectively known as the mesopontine tegmentum area or pontomesencephalotegmental complex.[6][7] In the basal forebrain, it originates from the basal optic nucleus of Meynert and medial septal nucleus:
Plasticity[edit]
Excitability and inhibition[edit]
Acetylcholine also has other effects on neurons. One effect is to cause a slow depolarization[citation needed] by blocking a tonically active K+ current, which increases neuronal excitability. In alternative fashion, acetylcholine can activate non-specific cation conductances to directly excite neurons.[10] An effect upon postsynaptic M4-muscarinic ACh receptors is to open inward-rectifier potassium ion channel (Kir) and cause inhibition.[11] The influence of acetylcholine on specific neuron types can be dependent upon the duration of cholinergic stimulation. For instance, transient exposure to acetylcholine (up to several seconds) can inhibit cortical pyramidal neurons via M1 type muscarinic receptors that are linked to Gq-type G-protein alpha subunits. M1 receptor activation can induce calcium-release from intracellular stores, which then activate a calcium-activated potassium conductance, which inhibits pyramidal neuron firing.[12] On the other hand, tonic M1 receptor activation is strongly excitatory. Thus, ACh acting at one type of receptor can have multiple effects on the same postsynaptic neuron, depending on the duration of receptor activation.[13] Recent experiments in behaving animals have demonstrated that cortical neurons indeed experience both transient and persistent changes in local acetylcholine levels during cue-detection behaviors.[14]
In the cerebral cortex, tonic ACh inhibits layer 4 medium spiny neurons, the main targets of thalamocortical inputs while exciting pyramidal cells in layers 2/3 and layer 5.[11] This filters out weak sensory inputs in layer 4 and amplifies inputs that reach the layers 2/3 and layer L5 excitatory microcircuits. As a result, these layer-specific effects of ACh might function to improve the signal noise ratio of cortical processing.[11] At the same time, acetylcholine acts through nicotinic receptors to excite certain groups of inhibitory interneurons in the cortex, which further dampen down cortical activity.[15]
Role in decision making[edit]
One well-supported function of acetylcholine (ACh) in cortex is increased responsiveness to sensory stimuli, a form of attention. Phasic increases of ACh during visual,[16] auditory [17] and somatosensory [18] stimulus presentations have been found to increase the firing rate of neurons in the corresponding primary sensory cortices. When cholinergic neurons in the basal forebrain are lesioned, animals' ability to detect visual signals was robustly and persistently impaired.[19] In that same study, animals' ability to correctly reject non-target trials was not impaired, further supporting the interpretation that phasic ACh facilitates responsiveness to stimuli. Looking at ACh's effect on thalamocortical connections, a known pathway of sensory information, in vitro application of cholinergic agonist carbachol to mouse auditory cortex enhanced thalamocortical activity.[20] In addition, Gil et al. (1997) applied a different cholinergic agonist, nicotine, and found that activity was enhanced at thalamocortical synapses.[21] This finding provides further evidence for a facilitative role of ACh in transmission of sensory information from the thalamus to selective regions of cortex.
An additional suggested function of ACh in cortex is suppression of intracortical information transmission. Gil et al. (1997) applied the cholinergic agonist muscarine to neocortical layers and found that excitatory post-synaptic potentials between intracortical synapses were depressed.[21] In vitro application of cholinergic agonist carbachol to mouse auditory cortex suppressed intracortical activity as well.[20] Optical recording with a voltage-sensitive dye in rat visual cortical slices demonstrated significant suppression in intracortical spread of excitement in the presence of ACh.[22]
Some forms of learning and plasticity in cortex appear dependent on the presence of acetylcholine. Bear et al. (1986) found that the typical synaptic remapping in striate cortex that occurs during monocular deprivation is reduced when there is a depletion of cholinergic projections to that region of cortex.[23] Kilgard et al. (1998) found that repeated stimulation of the basal forebrain, a primary source of ACh neurons, paired with presentation of a tone at a specific frequency, resulted in remapping of the auditory cortex to better suit processing of that tone.[24] Baskerville et al. (1996) investigated the role of ACh in experience-dependent plasticity by depleting cholinergic inputs to the barrel cortex of rats.[25] The cholinergic-depleted animals had a significantly reduced amount of whisker-pairing plasticity. Apart from the cortical areas, Crespo et al. (2006) found that the activation of nicotinic and muscarinic receptors in the nucleus accumbens is necessary for the acquisition of an appetitive task.[26]
ACh has been implicated in the reporting of expected uncertainty in the environment [27] based both on the suggested functions listed above and results recorded while subjects perform a behavioral cuing task. Reaction time difference between correctly cued trials and incorrectly cued trials, called the cue validity, was found to vary inversely with ACh levels in primates with pharmacologically (e.g. Witte et al., 1997) and surgically (e.g. Voytko et al., 1994) altered levels of ACh.[28][29] The result was also found in Alzheimer's disease patients (Parasuraman et al., 1992) and smokers after nicotine (an ACh agonist) consumption.[30][31] The inverse covariance is consistent with the interpretation of ACh as representing expected uncertainty in the environment, further supporting this claim.
Cut and paste fo the function of Acetylcholine -
Acetylcholine has functions both in the peripheral nervous system (PNS) and in the central nervous system (CNS) as a neuromodulator. Its receptors have very high binding constants.
In the peripheral nervous system, acetylcholine activates muscles, and is a major neurotransmitter in the autonomic nervous system.
In the central nervous system, acetylcholine and the associated neurons form a neurotransmitter system, the cholinergic system, which tends to cause anti-excitatory actions.
In the peripheral nervous system[edit]
In the peripheral nervous system, acetylcholine activates muscles, and is a major neurotransmitter in the autonomic nervous system. Acetylcholine binds to acetylcholine receptors on skeletal muscle fibers, it opens ligand-gated sodium channels in the cell membrane. Sodium ions then enter the muscle cell, initiating a sequence of steps that finally produce muscle contraction. Although acetylcholine induces contraction of skeletal muscle, it acts via a different type of receptor (muscarinic) to inhibit contraction of cardiac muscle fibers.
In the autonomic nervous system, acetylcholine is released in the following sites:
- all pre- and post-ganglionic parasympathetic neurons
- all preganglionic sympathetic neurons
- ganglionic sympathetic fibers to suprarenal medulla, the modified sympathetic ganglion; on stimulation by acetylcholine, the suprarenal medulla releases epinephrine and norepinephrine
- some postganglionic sympathetic fibers
- sudomotor neurons to sweat glands.
Damage to the cholinergic (acetylcholine-producing) system in the brain has been shown to be plausibly associated with the memory deficits associated with Alzheimer's disease.[4] ACh has also been shown to promote REM sleep.[5]
Pathways[edit]
There are three ACh pathways in the CNS.[citation needed]
- Pons to thalamus and cortex
- Magnocellular forebrain nucleus to cortex
- Septohippocampal
Acetylcholine is a polyatomic cation. It and the associated neurons form a neurotransmitter system, the cholinergic system from the brainstem and basal forebrain that projects axons to many areas of the brain. In the brainstem it originates from the Pedunculopontine nucleus and laterodorsal tegmental nucleus collectively known as the mesopontine tegmentum area or pontomesencephalotegmental complex.[6][7] In the basal forebrain, it originates from the basal optic nucleus of Meynert and medial septal nucleus:
- The pontomesencephalotegmental complex acts mainly on M1 receptors in the brainstem, deep cerebellar nuclei, pontine nuclei, locus caeruleus, raphe nucleus, lateral reticular nucleus and inferior olive.[7] It also projects to the thalamus, tectum, basal ganglia and basal forebrain.[6]
- Basal optic nucleus of Meynert acts mainly on M1 receptors in the neocortex.
- Medial septal nucleus acts mainly on M1 receptors in the hippocampus and neocortex.
Plasticity[edit]
Excitability and inhibition[edit]
Acetylcholine also has other effects on neurons. One effect is to cause a slow depolarization[citation needed] by blocking a tonically active K+ current, which increases neuronal excitability. In alternative fashion, acetylcholine can activate non-specific cation conductances to directly excite neurons.[10] An effect upon postsynaptic M4-muscarinic ACh receptors is to open inward-rectifier potassium ion channel (Kir) and cause inhibition.[11] The influence of acetylcholine on specific neuron types can be dependent upon the duration of cholinergic stimulation. For instance, transient exposure to acetylcholine (up to several seconds) can inhibit cortical pyramidal neurons via M1 type muscarinic receptors that are linked to Gq-type G-protein alpha subunits. M1 receptor activation can induce calcium-release from intracellular stores, which then activate a calcium-activated potassium conductance, which inhibits pyramidal neuron firing.[12] On the other hand, tonic M1 receptor activation is strongly excitatory. Thus, ACh acting at one type of receptor can have multiple effects on the same postsynaptic neuron, depending on the duration of receptor activation.[13] Recent experiments in behaving animals have demonstrated that cortical neurons indeed experience both transient and persistent changes in local acetylcholine levels during cue-detection behaviors.[14]
In the cerebral cortex, tonic ACh inhibits layer 4 medium spiny neurons, the main targets of thalamocortical inputs while exciting pyramidal cells in layers 2/3 and layer 5.[11] This filters out weak sensory inputs in layer 4 and amplifies inputs that reach the layers 2/3 and layer L5 excitatory microcircuits. As a result, these layer-specific effects of ACh might function to improve the signal noise ratio of cortical processing.[11] At the same time, acetylcholine acts through nicotinic receptors to excite certain groups of inhibitory interneurons in the cortex, which further dampen down cortical activity.[15]
Role in decision making[edit]
One well-supported function of acetylcholine (ACh) in cortex is increased responsiveness to sensory stimuli, a form of attention. Phasic increases of ACh during visual,[16] auditory [17] and somatosensory [18] stimulus presentations have been found to increase the firing rate of neurons in the corresponding primary sensory cortices. When cholinergic neurons in the basal forebrain are lesioned, animals' ability to detect visual signals was robustly and persistently impaired.[19] In that same study, animals' ability to correctly reject non-target trials was not impaired, further supporting the interpretation that phasic ACh facilitates responsiveness to stimuli. Looking at ACh's effect on thalamocortical connections, a known pathway of sensory information, in vitro application of cholinergic agonist carbachol to mouse auditory cortex enhanced thalamocortical activity.[20] In addition, Gil et al. (1997) applied a different cholinergic agonist, nicotine, and found that activity was enhanced at thalamocortical synapses.[21] This finding provides further evidence for a facilitative role of ACh in transmission of sensory information from the thalamus to selective regions of cortex.
An additional suggested function of ACh in cortex is suppression of intracortical information transmission. Gil et al. (1997) applied the cholinergic agonist muscarine to neocortical layers and found that excitatory post-synaptic potentials between intracortical synapses were depressed.[21] In vitro application of cholinergic agonist carbachol to mouse auditory cortex suppressed intracortical activity as well.[20] Optical recording with a voltage-sensitive dye in rat visual cortical slices demonstrated significant suppression in intracortical spread of excitement in the presence of ACh.[22]
Some forms of learning and plasticity in cortex appear dependent on the presence of acetylcholine. Bear et al. (1986) found that the typical synaptic remapping in striate cortex that occurs during monocular deprivation is reduced when there is a depletion of cholinergic projections to that region of cortex.[23] Kilgard et al. (1998) found that repeated stimulation of the basal forebrain, a primary source of ACh neurons, paired with presentation of a tone at a specific frequency, resulted in remapping of the auditory cortex to better suit processing of that tone.[24] Baskerville et al. (1996) investigated the role of ACh in experience-dependent plasticity by depleting cholinergic inputs to the barrel cortex of rats.[25] The cholinergic-depleted animals had a significantly reduced amount of whisker-pairing plasticity. Apart from the cortical areas, Crespo et al. (2006) found that the activation of nicotinic and muscarinic receptors in the nucleus accumbens is necessary for the acquisition of an appetitive task.[26]
ACh has been implicated in the reporting of expected uncertainty in the environment [27] based both on the suggested functions listed above and results recorded while subjects perform a behavioral cuing task. Reaction time difference between correctly cued trials and incorrectly cued trials, called the cue validity, was found to vary inversely with ACh levels in primates with pharmacologically (e.g. Witte et al., 1997) and surgically (e.g. Voytko et al., 1994) altered levels of ACh.[28][29] The result was also found in Alzheimer's disease patients (Parasuraman et al., 1992) and smokers after nicotine (an ACh agonist) consumption.[30][31] The inverse covariance is consistent with the interpretation of ACh as representing expected uncertainty in the environment, further supporting this claim.
