Pathways & Symptoms of Schizophrenia

What is the relationship between Mesolimbic Pathway and Positive Symptoms?

The positive symptoms of schizophrenia, such as delusions and hallucinations, are thought to result from excess activity in the mesolimbic dopaminergic pathways. Hyperactivity in these pathways could also account for the psychotic symptoms seen in drug-induced psychosis, mania, depression, or dementia.

What is the relationship beyween Mesocortical Pathway and Negative/Cognitive Symptoms?

Deficits in mesocortical dopamine concentrations are believed to be involved in the development of negative symptoms (e.g., alogia and anhedonia) and some cognitive deficits associated with schizophrenia. Furthermore, ongoing degeneration of the mesocortical pathway may account for the progressive worsening of symptoms seen in some people with schizophrenia.

What is the relationship between the Nigrostriatal Pathway and Extrapyramidal Symptoms?

Normal dopamine function in this pathway helps control movements, while deficiencies may cause movement disorders. For example, dopamine deficiencies in the nigrostriatal pathway can cause extrapyramidal symptoms (EPS), such as akathisia, dystonia, and akinesia. The nigrostriatal pathway is important in schizophrenia because antipsychotic drugs (especially typical antipsychotics) may block D2 receptors, decreasing function in this pathway and resulting in EPS-related side effects. Antipsychotic-induced dystonia and akinesia are also sometimes called pseudoparkinsonism because they mimic the symptoms of Parkinson’s disease.

What is the relationship between Tuberoinfundibular Pathway and Hyperprolactinemia?

Normal dopaminergic function in this pathway inhibits the release of prolactin, a pituitary hormone that triggers lactation. During pregnancy, dopaminergic function in this pathway decreases naturally, resulting in an increased secretion of prolactin and thus allows for breastfeeding. The tuberoinfundibular pathway is relevant to schizophrenia because when antipsychotic drugs block dopamine receptors in this pathway, the result is hyperprolactinemia, an adverse effect that can lead to amenorrhea (cessation of menstruation) in women and sexual dysfunction, breast enlargement, and galactorrhea (breast secretions) in both men and women.