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Neurotransmitter



  Neurotransmitters are chemicals that are used to relay, amplify and modulate signals between a neuron and another cell. According to the prevailing beliefs of the 1960s, a chemical can be classified as a neurotransmitter if it meets the following conditions:

  • There are precursors and/or synthesis enzymes located in the presynaptic neuron;
  • The chemical must be present in the presynaptic element
  • It is available in sufficient quantity in the presynaptic neuron to affect the postsynaptic neuron;
  • There must be postsynaptic receptors and the ability for the chemical to bind to said receptors
  • A biochemical mechanism for inactivation must be present.

Additional recommended knowledge

Contents

Types of neurotransmitters

There are many different ways to classify neurotransmitters. Often, dividing them into amino acids, peptides, and monoamines is sufficient for many purposes.

Some more precise divisions are as follows:

The major "workhorse" neurotransmitters of the brain are glutamic acid (=glutamate) and GABA.

Effects

Some examples of neurotransmitter action:

  • Acetylcholine - voluntary movement of the muscles
  • Norepinephrine - wakefulness or arousal
  • Dopamine - voluntary movement and motivation, "wanting", pleasure, associated with addiction and love
  • Serotonin - memory, emotions, wakefulness, sleep and temperature regulation
  • GABA (gamma aminobutyric acid) - inhibition of motor neurons
  • Glycine - spinal reflexes and motor behaviour
  • Neuromodulators - sensory transmission-especially pain

It is important to appreciate that it is the receptor that dictates the neurotransmitter's effect[citation needed]

Neurotransmitter systems

Neurons expressing certain types of neurotransmitters sometimes form distinct systems, where activation of the system causes effects in large volumes of the brain, called volume transmission.

The major neurotransmitter systems are the noradrenaline (norepinephrine) system, the dopamine system, the serotonin system and the cholinergic system.

Drugs targeting the neurotransmitter of such systems affects the whole system, and explains the mode of action of many drugs;

Diseases may affect specific neurotransmitter systems. For example, Parkinson's disease is at least in part related to failure of dopaminergic cells in deep-brain nuclei, for example the substantia nigra. Treatments potentiating the effect of dopamine precursors have been proposed and effected, with moderate success.

A brief comparison of the major neurotransmitter systems follows:

Neurotransmitter systems
System Origin [1] Effects[1]
Noradrenaline system locus coeruleus
  • arousal
  • reward
Lateral tegmental field
Dopamine system dopamine pathways:
  • mesocortical pathway
  • mesolimbic pathway
  • nigrostriatal pathway
  • tuberoinfundibular pathway
motor system, reward, cognition, endocrine, nausea
Serotonin system caudal dorsal raphe nucleus Increase (introverson), mood, satiety, body temperature and sleep, while decreasing nociception.
rostral dorsal raphe nucleus
Cholinergic system pontomesencephalotegmental complex
  • learning
  • short-term memory
  • arousal
  • reward
basal optic nucleus of Meynert
medial septal nucleus

Common neurotransmitters

Category Name Abbreviation Metabotropic Ionotropic
Small: Amino acids Aspartate - -
Neuropeptides N-Acetylaspartylglutamate NAAG Metabotropic glutamate receptors; selective agonist of mGluR3 -
Small: Amino acids Glutamate (glutamic acid) Glu Metabotropic glutamate receptor NMDA receptor, Kainate receptor, AMPA receptor
Small: Amino acids Gamma-aminobutyric acid GABA GABAB receptor GABAA receptor, GABAC receptor
Small: Amino acids Glycine Gly - Glycine receptor
Small: Acetylcholine Acetylcholine Ach Muscarinic acetylcholine receptor Nicotinic acetylcholine receptor
Small: Monoamine (Phe/Tyr) Dopamine DA Dopamine receptor -
Small: Monoamine (Phe/Tyr) Norepinephrine (noradrenaline) NE - -
Small: Monoamine (Phe/Tyr) Epinephrine (adrenaline) Epi - -
Small: Monoamine (Phe/Tyr) Octopamine - -
Small: Monoamine (Phe/Tyr) Tyramine -
Small: Monoamine (Trp) Serotonin (5-hydroxytryptamine) 5-HT Serotonin receptor, all but 5-HT3 5-HT3
Small: Monoamine (Trp) Melatonin Mel Melatonin receptor -
Small: Monoamine (His) Histamine H Histamine receptor -
PP: Gastrins Gastrin - -
PP: Gastrins Cholecystokinin CCK Cholecystokinin receptor -
PP: Neurohypophyseals Vasopressin Vasopressin receptor -
PP: Neurohypophyseals Oxytocin Oxytocin receptor -
PP: Neurohypophyseals Neurophysin I - -
PP: Neurohypophyseals Neurophysin II - -
PP: Neuropeptide Y Neuropeptide Y NY Neuropeptide Y receptor -
PP: Neuropeptide Y Pancreatic polypeptide PP - -
PP: Neuropeptide Y Peptide YY PYY - -
PP: Opioids Corticotropin (adrenocorticotropic hormone) ACTH Corticotropin receptor -
PP: Opioids Dynorphin - -
PP: Opioids Endorphin - -
PP: Opioids Enkephaline - -
PP: Secretins Secretin Secretin receptor -
PP: Secretins Motilin Motilin receptor -
PP: Secretins Glucagon Glucagon receptor -
PP: Secretins Vasoactive intestinal peptide VIP Vasoactive intestinal peptide receptor -
PP: Secretins Growth hormone-releasing factor GRF - -
PP: Somtostatins Somatostatin Somatostatin receptor -
SS: Tachykinins Neurokinin A - -
SS: Tachykinins Neurokinin B - -
SS: Tachykinins Substance P - -
PP: Other Bombesin - -
PP: Other Gastrin releasing peptide GRP - -
Gas Nitric oxide NO - -
Gas Carbon monoxide CO - -
Other Anandamide AEA Cannabinoid receptor -
Other Adenosine triphosphate ATP P2Y12 P2X receptor

See also

References

  1. ^ a b Rang, H. P. (2003). Pharmacology. Edinburgh: Churchill Livingstone, page 474 for noradrenaline system, page 476 for dopamine system, page 480 for serotonin system and page 483 for cholinergic system.. ISBN 0-443-07145-4. 
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Neurotransmitter". A list of authors is available in Wikipedia.
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