Final answer:
Dopamine D2-receptor antagonists work by blocking dopamine receptors and preventing dopamine from binding, which reduces dopamine neurotransmission.
Step-by-step explanation:
The mechanism of action of dopamine D2-receptor antagonists involves blocking dopamine receptors, thereby decreasing dopamine binding.
These antagonists attach to the D2 receptors, which prevents dopamine, the natural neurotransmitter, from binding to these receptors. Due to the blockage, dopamine is unable to exert its action on the postsynaptic neurons, which can help in reducing symptoms of diseases such as schizophrenia that are caused by overactive dopamine neurotransmission.
As for psychoactive drugs, they can act as either agonists or antagonists in the brain. Agonists increase neurotransmitter activity, while antagonists decrease it. In this context, antagonists block the receptors without activating them, therefore preventing the neurotransmitter from signaling information to adjacent neurons, which is the case with antipsychotics used in treating schizophrenia.