Figure 4. The orthosteric mAChR agonist xanomeline restores the learning and memory deficit in prion-infected mice.

(A) Chemical structure of xanomeline. (B) [³⁵S]-GTPγS binding to membranes prepared from control or prion-infected mice (9–10 w.p.i.) in response to xanomeline are expressed as a percentage of the maximal response observed with oxotremorine-M. Mean pEC₅₀ for xanomeline on control membranes = 7.67 ± 0.04, prion 9 w.p.i. membranes = 7.73 ± 0.06, and prion 10 w.p.i. membranes = 7.65 ± 0.13. n = 3. (C) [³⁵S]-GTPγS binding to membranes prepared from the frontal cortex of control or AD patients in response to xanomeline. Data are expressed as the percentage of the maximal [³⁵S]-GTPγS binding stimulated by oxotremorine-M. Mean pEC₅₀ values of 8.14 ± 0.28 (control) and 7.34 ± 0.36 (AD). n = 3. (D) Fear-conditioning response of control and prion-infected mice following administration of vehicle or xanomeline (5 mg/kg) 30 minutes prior to training and retrieval. n ≥ 6. Statistical analysis by 1 -way ANOVA. **P < 0.01. (E) Burrowing response of control and prion-infected mice following administration of vehicle or xanomeline (5 mg/kg) 30 minutes before each burrowing session (from 7 w.p.i.). (F, G, and H ) AUC of AMPA receptor–mediated currents before and after treatment with xanomeline in control (F, n = 10) and prion-infected (G and H, n = 12) hippocampi. *P < 0.05, paired Student’s t test. Also shown in G are representative traces of paired whole cell CA1 glutamatergic current recordings in vehicle-treated (black) and xanomeline-treated (100 nM) (red) hippocampal slices of a prion-infected mouse. (I) Western blot of hippocampal lysates prepared from prion-infected mice treated with vehicle or xanomeline (Xan, 5 mg/kg) and probed with an antibody that detects phospho-S880 of GluR2 AMPA receptor subunits (total GluR2 was used as a loading control). (J) Quantification of I. n = 3. **P < 0.01, paired Student’s t test. Data are shown as mean ± SEM.