The chemical bases of communication among neurons and the chemical regulation or modulation of this communication are affected by psychopharmacologic agents. These drugs can alter all of the known chemical neurotransmitters, including: amino acid transmitters (e.g., g-amino-butyric acid [GABA], glycine, taurine, beta-alanine, glutamate, aspartate, cysteic acid), acetylcholine, catecholamines (e.g., norepinephrine, epinephrine, dopamine), indoleamines (e.g., serotonin), histamine, and neuroactive peptides (e.g., pro-opiomelanocortin [POMC], b-endorphin, leu-
cine-enkephalin, methionine-enkephalin, dynorphin, neuropeptide-Y). Psychopharmacologic agents also can alter neuromodulators and chemicals that affect body functions, including: adrenocorticotrophin hormone (ACTH), corticotropin releasing factor (CRF), corticosteroids, and many peptides (e.g., Substance P, galanin, cholecystokinin [CCK], neurotensin, vaso-pressin, antidiuretic hormone [ADH], thyrotropin releasing hormone [TRH]). In addition to these relatively large molecules, psychopharmacologic agents can affect chemical ions (charged particles, such as Na +, Ca++,K+,Mg++, Cl")that alter neuronal transmission. Further, psychopharmacologic agents can affect second messengers (e.g., cyclic adenosine monophosphate [cAMP], guanine diphosphate [GDP], nerve growth factor [NGF]) and G-proteins that act to modulate neuronal communication. Genes with altered expression after drug exposure also are under investigation. Evaluations of these actions are active topics of research.
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