Schizophrenia is a complex disorder, generally believed to arise from dysregulation of dopamine and glutamate neurotransmission pathways. Current front-line treatment comprises the atypical antipsychotics, which provide symptomatic relief but are associated with significant side-effects. These agents are broad-spectrum GPCR antagonists that act primarily at the dopamine and serotonin receptors.
Muscarinic acetylcholine (mACh) receptors regulate dopamine levels in areas of the brain associated with psychosis, with the M4 subtype speculated to be a key regulator of dopaminergic hyperactivity. The absence of subtype-selective modulators has, however, hindered validation of this hypothesis. Now scientists at Lilly have reported (PNAS, 5th August 2008) a selective small molecule, LY2033298, that targets the M4 subtype.
The compound has been shown to act at an allosteric site on the receptor, potentiating agonist binding while having little effect on antagonist binding. The authors have further demonstrated in vivo activity in preclinical models that are predictive of antipsychotic drug effects.