General Mode of Action

GENERAL MODE OF ACTION

All antipsychotics except cloazapine have potent dopamine (D2) receptor blocking action. Phenothiazines and thioxanthanes also block D1, D3, and D4 receptors and have correlation with antipsychotic or tranquillizing property. Blockade of the dopaminergic projections to the temporal and the prefrontal area constitutes the limbic system, and in the mesocortical area, it is probably responsible for antipsychotic action. As an to adaptive change, to blockades of D2 receptor, the firing of DA neurons and DA turnover increases initially. However, over a period of time, this subsides and gives away diminished activity, especially in the basal to ganglia corresponding to the emergency of Parkinsons disease. Clozapine and other atypical antipsychotics have significant 5-HT2 and α1 blocking action and are relatively selective for D4 receptor. Thus, antipsychotic property depends on a specific profile of action of the drugs on several neurotransmitter receptors.