PSYCH 4Y03 Lecture Notes - Lecture 7: Locus Coeruleus, Substantia Nigra, Aromatic L-Amino Acid Decarboxylase
8 Apr 2017
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Trace amines: phenethylamine, tyramine, tryptamine, n-methylphenethylamine, 3- iodothyronamine, octopamine. Catecholamines are derived from the essential amino acid, tyrosine. They include dopamine (da), norepinephrine (ne) at sympathetic junction w/ target organs, and epinephrine/adrenaline: activated in stress and emergency reactions. Tyrosine requires active transport to the brain, and competes with other amino acids such as phenylalanine and tryptophan. Norepinephrine is a hormone at the adrenal medulla, and neurotransmitter in brain. tyrosine hydroxylase dopa decarboxylase. Da and ne are central neurotransmitters, acting in circuits of general activation. Stimulant drugs like amphetamines, cocaine, and ritalin (methylphenidate) all activate. Da systems, inducing wakefulness, suppressing appetite, improving concentration in small doses but inducing motor perseveration and other problems in high doses. Epi = 80% of what adrenal medulla secretes during emergency rxn (vs. 20% ne) There are two types of receptors for adrenergic receptors (alpha and beta) Ne binds mostly with alpha-receptors at sympathetic fibre terminals but can also affect beta-1 receptors.
