For each description, choose the neurotransmitter with which it is usually associated: Ingestion of l-tryptophan increases the levels of this substance in the brain.
High-Yield Explanation
The amino acid l-tryptophan is the precursor for serotonin, which is a neurotransmitter needed for non-rapid-eye-movement (NREM) sleep as well as for mood and pain modulation. Up to 70 to 90% of brain norepinephrine is produced in the pontine nucleus, locus ceruleus. Dopamine is implicated in schizophrenia and also in an impoant neurotransmitter for the extra-pyramidal system. Depletion of this substance, as in parkinsonism, causes muscular rigidity and tremors. Acetylcholine is the neurotransmitter associated with higher coical functioning and is depleted in Alzheimer's disease. Acetylcholine also is an impoant neurotransmitter for the autonomic nervous system (parasympathetic system and the sympathetic nerves to the sweat glands). Many antidepressants have an anticholinergic action, thus dryness of the mouth, constipation, and blurred vision. GABA is an impoant inhibitory transmitter that opens the chloride channels directly associated with the GABA receptors, hyperpolarizing the cell. Ref: Meltzer H.Y., Bobo W.V., Heckers S.H., Fatemi H.S. (2008). Chapter 16. Schizophrenia. In M.H. Ebe, P.T. Loosen, B. Nurcombe, J.F. Leckman (Eds),CURRENT Diagnosis & Treatment: Psychiatry, 2e.