The laminar cortical distribution of the [125I]
alpha-bungarotoxin, [3H]
cytisine and [3H]
epibatidine nicotinic acetylcholine receptor ligands was investigated by quantitative autoradiography in autopsy tissue from the cingulate, orbitofrontal and temporal cortices of control and
schizophrenia subjects matched for age and smoking history. Different laminar binding patterns were observed for the various nicotinic
ligands both in schizophrenic and control brains. [125I]
alpha-Bungarotoxin binding was distributed homogeneously across all cortical layers in all three brain regions, with highest binding densities in the cingulate cortex. [3H]
Cytisine and [3H]
epibatidine binding varied across the cortical ribbon, with high binding in layers I, III, V and VI, within the three cortical regions. A significantly reduced [125I]
alpha-bungarotoxin binding (-54%) was observed in the cingulate cortex of
schizophrenia subjects, in comparison with normal individuals who smoked tobacco. In the same brain region also a significantly higher [3H]
cytisine binding (48-77%) was observed in nearly all layers, except for layer I of the
schizophrenia subjects, when compared to normal individuals with a history of tobacco use. No significant changes in [3H]
epibatidine binding was observed within the individual cortical layers between control subjects and patients with
schizophrenia, but when calculated as a whole region (i.e. measurements performed across the whole cortical ribbon), the temporal cortex showed a significant increase in [3H]
epibatidine binding in
schizophrenia subjects compared to control subjects. The results suggest opposite changes of the alpha4beta2 and alpha7
nicotinic receptor subtypes in the cingulate cortex of patients with
schizophrenia which might reflect involvement of two different
nicotinic receptor mechanisms in
schizophrenia brain.