Cholinergic neurotransmission system

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. 

For almost one century, acetylcholine has been recognized as a neurotransmitter both in the central nervous system and the peripheral nervous system. In the peripheral nervous system, acetylcholine has been identified as the neurotransmitter of autonomic ganglia and the neuromuscular junction. Acetylcholine is involved in different peripheral functions such as heart rate, blood flow, gastrointestinal tract motility, and sweat production and smooth muscle activity. In the CNS, cholinergic neurotransmission plays a crucial role in a variety of CNS functions including sensory perception, motor function, cognitive processing, memory, arousal, attention, sleep, nociception, motivation, reward, mood, and psychosis. 

Nicotiana tabacum, and lobeline, present in the dried leaves and tops of the herb, Lobelia inflata (13). Both nicotine and lobeline act as agonists on a specific type of acetylcholine receptor, the nicotinic cholinergic receptor. In mammals, nicotinic cholinergic receptors mediate cholinergic neurotransmission in skeletal muscles, autonomic ganglia, and the central nervous system. At these sites nicotine s action has two phases, excitation and depression. Insect central nervous tissues are rich in nicotinic cholinergic receptors (cf. 14), but their role in behavior is not well understood. 

IIL FUNCTIONS ASSOCIATED WITH CHOLINERGIC NEUROTRANSMISSION IN THE CENTRAL NERVOUS SYSTEM... 

AChE and BuChE differ in their enzymatic properties and physiological function (M7, D4). However, there are other types of cholinesterases like benzoylcholinesterase and propionylcholinesterase. AChE splits neuromediator acetylcholine at the cholinergic synapses. It was also observed in erythrocytes but its function here is not yet known in detail. Like the function of BuChE activity in plasma, though, there is evidence that BuChE plays an important role in cholinergic neurotransmission and could be involved in other nervous system functions, in neurological diseases, and in nonspecific detoxification processes (D4). 

Nicotine stimulates central nicotine receptors and also affects other neurotransmission systems, increasing tyrosine hydroxylase activity and elevating noradrenaline (norepinephrine) release from the hippocampus [185], These effects have surprising kinetics since induced modifications persist long after treatment withdrawal. The administration of nicotine to patients raises certain problems, but this line of research has resulted in the development of compounds without the undesirable effects of nicotine itself and are referred to as cholinergic channel activators (for review see [186]). 

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