Serotonin as a Neurotransmitter

Serotonin, or 5-hydroxytryptamine (5-HT), is used as a neuro-transmitter by neurons with cell bodies in what are called the raphe nuclei that are located along the midline of the brain stem (see chapter 8). Serotonin is derived from the amino acid L-tryptophan, and variations in the amount of this amino acid in the diet (tryptophan-rich foods include milk and turkey) can affect the amount of serotonin produced by the neurons. Physiological functions attributed to serotonin include a role in the regulation of mood and behavior, appetite, and cerebral circulation.

Since LSD (a powerful hallucinogen) mimics the structure, and thus likely the function, of serotonin, scientists have long suspected that serotonin should influence mood and emotion. This suspicion is confirmed by the actions of the antidepressant drugs Prozac, Paxil, Zoloft, and Luvox, which act as serotonin-specific reuptake inhibitors (SSRIs). By blocking the reuptake of serotonin into presynaptic endings, and thereby increasing the effectiveness of serotonin transmission at synapses, these drugs have proven effective in the treatment of depression.

Serotonin's diverse functions are related to the fact that there are a large number of different subtypes of serotonin receptors— over a dozen are currently known. Thus, while Prozac may be

Zoloft Serotonin Transmission

G-proteins

Norepinephrine

G-proteins

Postsynaptic cell

Adenylate cyclase

Ion channel

Plasma membrane

Norepinephrine

Adenylate cyclase

Ion channel

Plasma membrane

G-protein subunit dissociates

Protein Membrane Plasmatic

Phosphorylates proteins

Figure 7.28 Norepinephrine action requires G-proteins. The binding of norepinephrine to its receptor (1) causes the dissociation of G-proteins (2). Binding of the alpha G-protein subunit to the enzyme adenylate cyclase (3) activates this enzyme, leading to the production of cyclic AMP (4). Cyclic AMP, in turn, activates protein kinase (5), which can open ion channels (6) and produce other effects.

G-protein subunit dissociates

Phosphorylates proteins

Figure 7.28 Norepinephrine action requires G-proteins. The binding of norepinephrine to its receptor (1) causes the dissociation of G-proteins (2). Binding of the alpha G-protein subunit to the enzyme adenylate cyclase (3) activates this enzyme, leading to the production of cyclic AMP (4). Cyclic AMP, in turn, activates protein kinase (5), which can open ion channels (6) and produce other effects.

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Responses

  • lodovico
    What is serotonin physiology?
    8 years ago
  • corey
    How seretonin works complete physiology?
    5 months ago
  • Latasha
    Is serotonin a hormone or transmitter?
    4 months ago

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