Do Antipsychotics Elicit Atypical Action by Blocking 5-HT Receptors?
In addition to blocking dopamine receptors, the new atypical antipsychotic drugs also block 5-HT receptors. Although it has often been suggested that the blockade of 5-HT2A receptors may alleviate the parkinsonism caused by D2 blockade (69,70), most data do not support this principle. Remoxipride Is an Important Exception Remoxipride is a highly effective atypical antipsychotic drug (not used in Canada) with no EPS and no hyperprolactinemia, yet it does not block 5-HT receptors. 5-HT Blockade Enhances Catalepsy Selective 5-HT2A receptor blockade with the drug M100,907 markedly enhances, instead of reducing, the catalepsy (catalepsy in animals = EPS in humans) observed with submaximal dosages of the D2 block by raclopride (71). No Dopamine5-HT Correlation to Cataleptic Dosages There is no correlation between the cataleptic dosages of neuroleptics and the ratio of the antipsychotic dissociation constants at D2 and at 5-HT2A receptors (72,73). No Sharp Separation of Typicals and Atypicals
