D2 Receptor: Hyperactive dopaminergic activity on D2 receptors in the mesolimbic pathway is responsible for the positive symptoms of schizophrenia (hallucinations, delusions, paranoia). After taking an antipsychotic, antagonism of D2 receptors occurs throughout the entire brain, leading to a number of deleterious side effects from D2 receptor antagonism throughout the entire dopamine pathway system. Unfortunately, it's not possible to affect D2 receptors only in the mesolimbic pathway. Fortunately, 5-HT2A receptor antagonism reverses these side effects to some extent. Reducing D2 dopaminergic activity in the mesolimbic pathway also results in an anhedonic effect, reducing pleasure, motivation, and the salience of one's life experience. In the mesocortical pathway to the DLPFC and VMPFC, endogenous D2 receptor dopamine activity is sometimes low in schizophrenia, resulting in cognitive, affective, and, broadly, the negative symptoms of schizophrenia. D2 receptor antagonism here further compounds these problems. In the nigrostratial pathway, D2 receptor antagonism results in extrapyramidal symptoms. If this antagonism occurs long enough, symptoms of EPS may become permanent, even if antipsychotic use is discontinued. In the tuberoinfundibular pathway, D2 receptor antagonism results in elevated prolactin. If prolactin levels become high enough, hyperprolactinaemia may occur, resulting in sexual dysfunction, weight gain, more rapid demineralization of bones, and possibly galactorrhea and amenorrhea.