Neurotransmission, cholinergic

Cholinergic neurotransmission ChEs terminate cholinergic transmission in the central nervous system (CNS), in NMJs and in the autonomic system (the parasympathetic system, somatic motor nerves and pre-ganglionic sympathetic nerves). A few sensory cells and the NMJ in nematodes also include ChEs. 

While these functions can be a carried out by a single transporter isoform (e.g., the serotonin transporter, SERT) they may be split into separate processes carried out by distinct transporter subtypes, or in the case of acetylcholine, by a degrading enzyme. Termination of cholinergic neurotransmission is due to acetylcholinesterase which hydrolyses the ester bond to release choline and acetic acid. Reuptake of choline into the nerve cell is afforded by a high affinity transporter (CHT of the SLC5 gene family). 

Evidence that cortical ACh regulates EEG of prefrontal cortex (Figs. 5.9 and 5.10) implies that manipulating pontine cholinergic neurotransmission alters... 

Ferguson, S. M., Bazalakova, M., Savchenko, V. et al. (2004). Lethal impairment of cholinergic neurotransmission in hemicholinium-3-sensitive transporter knockout mice. Proc. Natl Acad. Sci. USA 101, 8762-7. 

Fig. 1. Schematic drawing of the cholinergic neurotransmission. In case of ganglionic and neuro-muscular synapses, the receptor is of the nicotinic, sodium channel-coupled type, in case of synapses at the parasympathetic target organs, the receptor is of the muscarinic, G-protein-coupled type. The predominant ehinination pathway of the transmitter acetylcholine...

The consistent findings of cholinergic deficits in AD and their correlations with both pathological and clinical features have suggested cholinergic maintenance and replacement therapies similar to the dopaminergic treatment of patients with Parkinson s disease. Theoretically, an enhancement of cholinergic neurotransmission can be achieved in various ways [Davies 1981) ... 

Riemann D, Hohagen F, Bahro M, et al Cholinergic neurotransmission, REM sleep and depression. J Psychosom Res 38 [suppl l) 15-25, 1994 Rihmer Z, Arato M, Szadoczky E, et al The dexamethasone suppression test in psychotic versus nonpsychotic endogenous depression. Br J Psychiatry 145 508-511, 1984... 

The discovery that the toxins of Elapid snakes bind almost irreversibly to the AChR also facilitated the isolation and study of this receptor. The structure of these venoms has been elucidated those most widely used experimentally are the a-bungarotoxin (BTX) of the Indian cobra and the toxin of the Siamese cobra. These compounds are peptides containing from 61 to 74 amino acids, five disulfide bridges, and a high proportion of basic arginine and lysine residues, often in close proximity. Venoms are toxic because they block cholinergic neurotransmission by binding to the receptor. 

FIGURE 12—10. Acetylcholine (ACh) receptors. There are numerous receptors for ACh. The major subdivision is between nicotinic (N) and muscarinic (M) cholinergic receptors. There are also numerous subtypes of these receptors, best characterized for muscarinic receptor subtypes (Ml, M2, Mx). Perhaps the Ml postsynaptic receptor is key to mediating the memory functions linked to cholinergic neurotransmission, but a role for other cholinergic receptor subtypes has not been ruled out. 

Stahl, S.M. (1998) Enhancing cholinergic neurotransmission with the new cholinesterase inhibitors implications for Alzheimer s disease and cognitive disorders. Hospital Practice 33(11), 131-6. 

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