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Neurotransmitters and drugs
Neurotransmitters and some drugs that stimulate receptors are called agonists. Agonists stimulate receptors to their fullest signal transduction. Drugs that act as agonists are useful in patients who lack or are deficient in agonist neurotransmitters. In situations where the actions of a full agonist or partial agonists are undesirable, an antagonist is required to revert the receptor back to the state where no agonist exists, back to neutral. Partial agonists act as they sound, and produce a conformational change of a receptor that is halfway between the changes of a full agonist and the baseline conformation of that receptor. An antagonist can also reverse the effects of inverse agonists to the receptors baseline. An inverse agonist acts to change the conformation of a receptor to completely inactivate it and remove the baseline constitutive activity.
Compare and contrast the actions of g coupled proteins and ion gated channels.
Both G protein coupled receptors and Ion gated channels are a form of signal transduction cascades in the brain. They are both triggered by neurotransmitters, and many of the psychotropic drugs used today affect one of these two cascades. They both perform when an extracellular first messenger passes a message to an intracellular second messenger. However, G protein’s second messenger is a chemical, such as adenosine monophosphate, while the ion channel second messenger can be an ion, such as calcium. There are two classes of ion channels, Ligand gated and voltage sensitive ion channels. The ligand gated ion channels act similar to g protein receptors because they use the agonist spectrum. Voltage sensitive ion channels are opened and closed based on the voltage charge across the membrane.