Coupling of muscarinic receptors to GTP proteins in postmortem human brain — alterations in Alzheimer's disease (original) (raw)

The coupling of muscarinic agonist receptors to guanine nucleotide-binding (G) proteins was investigated in the frontal, temporal cortices and thalamus of control and Alzheimer brains by using carbachol in competition experiments with [3H]QNB. In the presence of GppNHp, the carbachol/ [~H]QNB competition binding data showed a 6-fold increase in the high-affinity muscarinic agonist coefficient (K~ h~gh) in the thalami of control brains and a significantly increased proportion of low-affinity agonist binding sites (Bmax ~ow) in the temporal cortices of control brains, while no significant effect of GppNHp was observed in Alzheimer brains. The results suggest a disturbance of the muscarinic recepto~G protein coupling in Alzheimer's disease.