Acetylcholine as neurotransmitter

Acenocoumarole, 331 Acephylline, 425 Acetaminophen, 111 Acetanilide, 111 Acetazolamide, 249 Acetohexamide, 138 Acetophenazine, 383 Acetyl methoxyprazine, 131 Acetylcholine, as neurotransmitter, 62 Acetylmethadol, 81 Aches, minor, 85 Acylureas, as hypnotics, 95, 220, 245 Addiction... 

Cholinergic. An agent that mimics acetylcholine. Also refers to neurons that utilize acetylcholine as a neurotransmitter. 

Parasympathetic nervous system. That portion of the autonomic nervous system that utilizes acetylcholine as the neurotransmitter at the neuro-effector junctions. 

After an overview of neurotransmitter systems and function and a consideration of which substances can be classified as neurotransmitters, section A deals with their release, effects on neuronal excitability and receptor interaction. The synaptic physiology and pharmacology and possible brain function of each neurotransmitter is then covered in some detail (section B). Special attention is given to acetylcholine, glutamate, GABA, noradrenaline, dopamine, 5-hydroxytryptamine and the peptides but the purines, histamine, steroids and nitric oxide are not forgotten and there is a brief overview of appropriate basic pharmacology. 

The concept of chemical neurotransmission originated in the 1920s with the classic experiments of Otto Loewi (which were themselves inspired by a dream), who demonstrated that by transferring the ventricular fluid of a stimulated frog heart onto an unstimulated frog heart he could reproduce the effects of a (parasympathetic) nerve stimulus on the unstimulated heart (Loewi Navratil, 1926). Subsequently, it was found that acetylcholine was the neurotransmitter released from these parasympathetic nerve fibers. As well as playing a critical role in synaptic transmission in the autonomic nervous system and at vertebrate neuromuscular junctions (Dale, 1935), acetylcholine plays a central role in the control of wakefulness and REM sleep. Some have even gone as far as to call acetylcholine a neurotransmitter correlate of consciousness (Perry et al., 1999). 

Cholinergic Relating to nerve cells or fibers that employ acetylcholine as their neurotransmitter. 

Somatic nerves originate in the CNS and terminate at the neuromuscular junction where acetylcholine is the transmitter. Nerves of the autonomic system also use acetylcholine as the neurotransmitter at the end of the preganglionic fibres within the ganglia. With few exceptions, the postganglionic sympathetic fibres secrete noradrenaline (norepinephrine) whilst postganglionic parasympathetic fibres secrete acetylcholine. 

Cholinergic Medications (Boosting Acetylcholine). As we ve previously told you, acetylcholine is the primary neurotransmitter that the brain uses for memory and intellectual processing. It was only a matter of time before medications that boost acetylcholine transmission were studied in dementia patients. 

So, parasympathetic nerves use acetylcholine as a neurotransmitter and cholinomimetic drugs mimic the action of acetylcholine at its receptors. Muscarinic receptor subtypes are found on neuroeffector junctions. Nicotinic receptor subtypes are found on ganglionic synapses. Chohnomimetics can be classified as ... 

To illustrate the action of ion channels in cell-to-cell signaling, we describe the mechanisms by which a neuron passes a signal along its length and across a synapse to the next neuron (or to a myocyte) in a cellular circuit, using acetylcholine as the neurotransmitter. 

In the following we attempt to describe the acetylcholinesterase/choline acetyltransferase enzyme system inside the neural synaptic cleft in a simple fashion see Figure 4.49. The complete neurocycle of the acetylcholine as a neurotransmitter is simulated in our model as a simple two-enzymes/two-compartments model. Each compartment is described as a constant-flow, constant-volume, isothermal, continuous stirred tank reactor (CSTR). The two compartments (I) and (II) are separated by a nonselective permeable membrane as shown in Figure 4.50. 

As indicated in Figure 18-1, the transmitter at the preganglionic-postganglionic synapse in both divisions is acetylcholine, as is the transmitter at the parasympathetic postganglionic-effector cell synapse. The transmitter at the sympathetic postganglionic-effector cell synapse is usually norepinephrine. A small number of sympathetic postganglionic fibers, however, also use acetylcholine as their neurotransmitter. 

In addition to their functions as presynaptic autoreceptors, 0C2AR can also modulate release of other neurotransmitters (Figure 3). In the CNS, 0C2A and 0C2C receptors inhibit dopamine release in basal ganglia (Bucheler et al. 2002) as well as serotonin secretion in mouse hippocampus and brain cortex (Scheibner et al. 2001a). In the enteric nervous system, the release of acetylcholine as determined by [3H] -choline overflow from tissue slices was selectively inhibited by (X2aAR (Scheibner et al. 2002). 

Acetylcholine is a neurotransmitter, a key substance involved with transmission of nerve impulses in the brain, skeletal muscles, and other areas where nerve impulses occur. An essential step in the proper function of any nerve impulse is its cessation (see Figure 6.9), which requires hydrolysis of acetylcholine as shown by Reaction 6.10.1. Some xenobiotics, such as organophosphate compounds (see Chapter 18) and carbamates (see Chapter 15) inhibit acetylcholinesterase, with the result that acetylcholine accumulates and nerves are overstimulated. Adverse effects may occur in the central nervous system, in the autonomic nervous system, and at neuromuscular junctions. Convulsions, paralysis, and finally death may result. 

Cholinergic stimulation Stimulation of the nerve fibers utilizing acetylcholine as the neurotransmitter. 

The signals between nerve cells are transmitted by chemicals known as neurotransmitters. Acetylcholine is an important neurotransmitter that is involved in the sig-... 

The preganglionic fibers terminating in the adrenal medulla, the autonomic ganglia (both parasympathetic and sympathetic), and the postganglionic fibers of the parasympathetic division use acetylcholine as a neurotransmitter (Figure 4.2). Cholinergic neurons innervate voluntary muscles of the somatic system and are also found in the CNS. 

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