Chronic treatment with choline or scopolamine indicates the presence of muscarinic cholinergic receptor plasticity in the frontal cortex of young but not of aged mice.

Chronic treatment (2 weeks) with either scopolamine (4 mg/kg, once daily p.o.) or choline (200 mg/kg, once daily p.o.) resulted in a pronounced muscarinic cholinergic receptor up- or down-regulation in the frontal cortex of young (4 weeks) but not of aged (18 months) female mice. It is speculated that a similar age-related decline of muscarinic receptor plasticity might contribute to the profound dysfunction of cholinergic neurotransmission in Alzheimer's disease.