Richard C. Deth, a professor of Pharmaceutical Science at Northeastern University, provides this answer:
Schizophrenia is a psychiatric disorder in which previously normal cognitive abilities and behaviors becomes disturbed. The most common age of onset is just after reaching adulthood, typically the late-teens to the mid-thirties. It is manifested either by so-called positive symptoms (delusions, hallucinations, unusual or disorganized behavior) or by negative symptoms, including a marked lack of activity, loss of interest and unresponsiveness.
Although the precise cause of schizophrenia remains unknown, an enormous amount of research has come up with a number of possibilities. Many early theories focused on behavioral or stress-induced events, but more recently, consensus holds that underlying biochemical abnormalities are more likely the cause. Lending great support to this idea is the fact that genetic predisposition may account for 50 percent of the risk of developing schizophrenia. Not surprisingly, these biochemical hypotheses center on dysfunction of the neurotransmitter systems in the brain, which provide for normal cognition and attention. The main theories include the Dopamine Hypothesis, the NMDA Receptor Hypothesis, the Single-carbon Hypothesis and the Membrane Hypothesis. And new research from our laboratory suggests that elements from each of these theories may play a role in schizophrenia.
  Image: HEALTHGUIDE DOPAMINE has been linked to schizophrenia. In a brain with schizophrenia, far more neurotransmitters are released between neurons (bottom), than are in a normal brain (top). |
The Dopamine Hypothesis: The notion that dopamine may be involved in schizophrenia derives from the therapeutic usefulness of drugs that block certain dopamine receptors in treating the disorder. Indeed, because dopamine blockers are so often effective, it has been proposed that an over activity of dopamine neurotransmission in cortical and limbic areas of the brain may cause schizophrenia. Drugs with selectivity for the D4 dopamine receptor (such as clozapine or olanzapine) can be particularly effective, and so this receptor subtype may play a critical role; in fact, elevated levels of D4 receptor binding have been found post-autopsy in the brains of persons who had schizophrenia. Dopamine is further implicated by the fact that a schizophrenia-like psychosis can be induced by abusing amphetamines, which act on dopamine pathways.
The NMDA Receptor Hypothesis: NMDA receptors respond to the excitatory neurotransmitter glutamate, and are known to be important for normal memory and cognition. Because drugs affecting NMDA receptors (such as ketamine or phencyclidine (PCP)) can cause schizophrenia-like hallucinations and because neuroleptic drugs, including clozapine, can inhibit their occurrence, it has been suggested that NMDA receptor dysfunction may cause schizophrenia. Recent studies have shown therapeutic benefit from drugs acting on NMDA receptors, such as glycine and D-cycloserine.
The Single-Carbon Hypothesis: Researchers have often linked disturbances of the single-carbon folate pathway to schizophrenia. This metabolic pathway provides carbon groups for a variety of biochemical reactions in the brain, including the synthesis of purine and pyrimidine nucleotides and the methyl-donating amino acid methionine. A number of studies have shown that methionine metabolism is impaired in most schizophrenic persons, and other work has demonstrated enzyme deficits in the folate pathway in some schizophrenic persons. These observations are clear, but their relationship to neuronal transmission has remained elusive.
See what we're tweeting about
3 Comments
Add Commentso,is schizophrenia a mixed up pathway of brain impulses or neurotransmitters?
Reply | Report Abuse | Link to thisI have been diagnoised by doctors with Manic Depression and some of the doctors said schizophrenia. I live a lonely exsistance due to lack of understanding by the community, and health care professionals. I have no friends here and people use what they know to hurt not help those with different disorders. Programs I found to be a place to house in daytime hours people with these serious disorders. Getting ahead financially isnot always something which can be done by these individuals so these are poor and viewed as nuts and some even fear them.
Reply | Report Abuse | Link to thistheresa
Schizophrenia is a sneaky mental illness. I came here looking for information about it. I was looking for new scientific research in this field. I’m going to use your paragraph about the membrane hypothesis in order to give an example to my readers (and post your link). I have an internal vision about what happens in the brain of a schizophrenic thanks to dream interpretation according to the scientific method. I’m going to relate this knowledge to the schizophrenic’s neurological reality. The origin of the chemical alterations that provoke various behavioral distortions is quite strange. Thank you for this information!
Reply | Report Abuse | Link to this