Phenothiazines primarily exert their effects by blocking what type of receptors in the brain?

Phenothiazines primarily exert their therapeutic effects by blocking dopamine receptors in the brain, particularly the D2 subtype. This mechanism is central to their role as antipsychotic medications, as it helps to reduce the positive symptoms of schizophrenia and other psychotic disorders. By antagonizing these receptors, phenothiazines inhibit dopamine transmission, which is often dysregulated in individuals experiencing psychosis.

Dopamine is a neurotransmitter that plays a key role in mood, perception, and cognition. In conditions like schizophrenia, there is often an overactivity of dopamine pathways, leading to symptoms such as hallucinations and delusions. The blockade of dopamine receptors by phenothiazines not only mitigates these symptoms but also aligns with the dopamine hypothesis of schizophrenia, which postulates that excessive dopaminergic activity contributes to the disorder's manifestation.

While norepinephrine and serotonin receptors are involved in various aspects of mood regulation and other neurological functions, phenothiazines do not primarily target these systems. Similarly, GABA receptors are associated with inhibitory neurotransmission and are not the main target of phenothiazine action. Understanding the specific targeting of dopamine receptors by phenothiazines is crucial for grasping how these medications function in the treatment of psychotic disorders.