Loss of [3H]4-DAMP binding to muscarinic receptors in the orbitofrontal cortex of Alzheimer's disease patients with psychosis.

S W Y Tsang, P T Francis, M M Esiri, P T H Wong, C P L H Chen, M K P Lai

Psychopharmacology 2008 Jun

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Neuropsychiatric behaviours in Alzheimer's disease (AD) patients have been associated with neocortical alterations of presynaptic cholinergic and muscarinic M2 receptor markers. In contrast, it is unclear whether non-M2 muscarinic receptors have a role to play in AD behavioural symptoms. To correlate the alterations of neocortical postsynaptic muscarinic receptors with clinical features of AD. [(3)H]4-DAMP were used in binding assays with lysates of Chinese hamster ovary (CHO) cells stably transfected with M1-M5 receptors. [(3)H]4-DAMP was further used to measure muscarinic receptors in the postmortem orbitofrontal cortex of aged controls and AD patients longitudinally assessed for cognitive decline and behavioural symptoms. [(3)H]4-DAMP binds to human postmortem brain homogenates and M1-, M3-, M4- and M5-transfected CHO lysates with subnanomolar affinity. Compared to the controls, the [(3)H]4-DAMP binding density is reduced only in AD patients with significant psychotic symptoms. The association between reduced [(3)H]4-DAMP binding and psychosis is independent of the effects of dementia severity or neurofibrillary tangle burden. This study suggests that the loss of non-M2 muscarinic receptors in the orbitofrontal cortex may be a neurochemical substrate of psychosis in AD and provides a rationale for further development of muscarinic receptor ligands in AD pharmacotherapy.

Citation

S W Y Tsang, P T Francis, M M Esiri, P T H Wong, C P L H Chen, M K P Lai. Loss of [3H]4-DAMP binding to muscarinic receptors in the orbitofrontal cortex of Alzheimer's disease patients with psychosis. Psychopharmacology. 2008 Jun;198(2):251-9