Which of the following substances is a natural hormone produced by the pineal gland that induces sleep?
A. Amphetamine
B. Melatonin
C. Methylphenidate
D. Pemoline
Correct Answer: B. Melatonin
Melatonin is a natural hormone that induces sleep. Melatonin is a hormone synthesized within the pineal gland from the amino acid tryptophan. Tryptophan is hydroxylated and then decarboxylated to form 5-hydroxytryptamine or serotonin. When there is sunlight, serotonin is stored within pinealocytes, making it unavailable to monoamine oxidase, the enzyme that converts serotonin to melatonin. All the others are medications classified as stimulants.
Option A: Amphetamine is a central nervous (CNS) system stimulant that functions by increasing the amounts of dopamine, norepinephrine, and serotonin (to a lesser extent) in the synaptic cleft through a variety of mechanisms. Amphetamine is FDA-approved for the treatment of attention-deficit/hyperactivity disorder (ADHD) and narcolepsy. It has indications as a first-line agent for ADHD in adults and children six years of age and older. Amphetamine is also a second-line agent for the treatment of narcolepsy.
Option C: Methylphenidate is FDA-approved for treating attention deficit hyperactivity disorder (ADHD) in children and adults and as a second-line treatment for narcolepsy in adults. Methylphenidate blocks the reuptake of two neurotransmitters, norepinephrine (NE) and dopamine, by presynaptic neurons. More specifically, it inhibits the transporters of these neurotransmitters, increasing the concentration of dopamine and NE in the synaptic cleft.
Option D: Pemoline is a stimulant drug of the 4-oxazolidinone class. It was first synthesized in 1913 but its activity was not discovered until the 1930s. Under the names Betanamin, Cylert, Tradon, and Ceractiv it was used as a medication to treat attention-deficit hyperactivity disorder (ADHD) and narcolepsy.
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