Most antipsychotic medications exert the following effects on the central nervous system (CNS)?
A. Stimulates the CNS by blocking postsynaptic dopamine, norepinephrine, and serotonin receptors.
B. Sedate the CNS by stimulating serotonin at the synaptic cleft.
C. Depress the CNS by blocking the postsynaptic transmission of dopamine, serotonin, and norepinephrine.
D. Depress the CNS by stimulating the release of acetylcholine.
Correct Answer: C. Depress the CNS by blocking the postsynaptic transmission of dopamine, serotonin, and norepinephrine.
The exact mechanism of antipsychotic medication action is unknown, but appears to depress the CNS by blocking the transmission of three neurotransmitters: dopamine, serotonin, and norepinephrine. The first-generation antipsychotics work by inhibiting dopaminergic neurotransmission. Their effectiveness is best when they block about 72% of the D2 dopamine receptors in the brain. They also have noradrenergic, cholinergic, and histaminergic blocking action.
Option A: Second-generation antipsychotics work by blocking D2 dopamine receptors as well as serotonin receptor antagonist action. the 5-HT2A subtype of serotonin receptor is most commonly involved. Second-generation antipsychotics are serotonin-dopamine antagonists and are also known as atypical antipsychotics. The Food and Drug Administration (FDA) has approved 12 atypical antipsychotics as of the year 2016. They are risperidone, olanzapine, quetiapine, ziprasidone, aripiprazole, paliperidone, asenapine, lurasidone, iloperidone, cariprazine, brexpiprazole, and clozapine.
Option B: First and second-generation antipsychotics (except clozapine) are indicated for the treatment of an acute episode of psychoses as well as maintenance therapy of schizophrenia and schizoaffective disorders. First-generation antipsychotics are better for treating positive symptoms of schizophrenia, e.g., hallucinations, delusions, among others. They also decrease the risk of a repeat episode of psychosis. Second-generation antipsychotics treat both positive symptoms and negative symptoms of schizophrenia, e.g., withdrawal, ambivalence, among others, and are known to reduce relapse rates.
Option D: They don’t sedate the CNS by stimulating serotonin, and they don’t stimulate neurotransmitter action or acetylcholine release. First-generation antipsychotics are effective in the treatment of acute mania with psychotic symptoms. All second-generation antipsychotics except clozapine can also be used as a treatment of symptoms of acute mania. Antipsychotics are used with mood stabilizers like lithium, valproic acid, or carbamazepine initially, and then after symptoms stabilize can be gradually decreased and withdrawn.