The second view is that neuroleptic drugs primary interact with “ sigma opiate” receptors.

The third is that interaction with one or more the newer D-receptor subtypes explain the action of these drugs. Whatever the underlying mechanism, acute blockade of any known receptor population is not, in isolation, a sufficient explanation for antipsychotic action.

This model fails to explain the antipsychotic activity of clozapine which has weak D2 blocking action. However, it has significant 5-HT and á1-adrenoceptor blocking action and is relatively selective for D4 receptors. Thus, antipsychotic action may depend on a specific profile of action of the drugs on several neurotransmitter receptors.(Fig 11)