Final answer:
The mechanism of action of phenothiazine antipsychotics involves dopamine receptor blockade.
Step-by-step explanation:
The mechanism of action of phenothiazine antipsychotics involves dopamine receptor blockade. These drugs are antagonists for dopamine, meaning they block dopamine's effects by binding its receptors without activating them. This prevents dopamine released by one neuron from signaling information to adjacent neurons.