There are strong arguments for the assumption that biochemical factors play a role in schizophrenia. Recent development of scanning technologies have enabled researchers to look for abnormalities in biochemical functioning. For example, research using PET scans shows that people whose schizophrenic behavior is long standing & chronic, tend to have lower level of metabolism in their frontal & temporal lobes & a somewhat higher flow at the base of the skull. Antipsychotic drugs are known to produce certain biochemical changes in brain, as well as positive changes in behavior.
Just as neurotransmitters are thought to be important in at least some types of mood disorders, biologically oriented research on schizophrenia also emphasizes the importance of neurotransmitter functioning. For many years, Dopamine Hypothesis was the most widely accepted explanation for biochemical pathology in schizophrenia. The hypothesis, simply stated, says that an excess of dopamine at certain synapses in brain is associated with schizophrenia. The strongest support for a connection between dopamine function & schizophrenia came from research in 1970s that showed that the clinical effectiveness of certain antipsychotic drugs like Chlorpromazine depends on their ability to block dopamine receptors.
Recent research, however, has demonstrated that (1) there actually are five types of dopamine receptors, which differ in their cerebral distribution & (2) biochemical processes & substances, other than those involving dopamine also play important roles in schizophrenia and it's treatment (Bradford et al., 2002). One such substance is SEROTONIN, which may be important, but which has been investigated much less in relation to schizophrenia than dopamine. Another is GLUTAMATE, the most widely distributed neuro- transmitter in the brain. Because of the difficulty of unambiguously confirming the dopamine hypothesis it's likely that in future, more complex hypotheses will be developed that incorporate the roles played by recently identified neurotransmitters and process related to them