Increased concentrations and lateral asymmetry of amygdala dopamine in schizophrenia

There is a growing body of evidence in support of the view of schizophrenia as a dysfunction of the left temporal lobe. This hypothesis, first proposed by Flor-Henry, stemmed from the frequently observed association of schizophreniform psychoses with left-sided temporal lobe epilepsy. As yet the evidence is solely clinical, with a wide range of psychological and physiological measurements indicating a left hemisphere disorder in patients with schizophrenia. It is not, however, inconsistent with the major neurochemical hypothesis of schizophrenia, which proposes an increase in dopaminergic neurotransmission which can be blocked by neuroleptic drugs. One region of the medial temporal lobe, the amygdala, receives a major dopaminergic innervation from the ventral tegmental area. In fact this meso-limbic dopaminergic tract, which also innervates the nucleus accumbens and olfactory tubercule, has been implicated in psychosis and in antipsychotic drug action. We have attempted here to test whether there is a neurochemical correlate of the Flor-Henry hypothesis using brain tissue collected post mortem from schizophrenic patients and controls. The results indicate that a specific increase of dopamine is found in the amygdalae in the left cerebral hemisphere of the schizophrenic group.