Age-dependent decrease in the negative inotropic effect of carbachol on isolated human right atrium

On isolated, electrically driven human right atrial strips, carbachol (10 −8–10 −3 M) concentration-dependently decreased force of contraction prestimulated with 1 μM forskolin; maximal negative inotropic effects of carbachol (10 −6–3×10 −6 M), however, were in atria from patients aged 70 years (mean age: 73.8±0.6 years, n=11). We conclude that, in human right atrium, the recently described age-dependent decrease in muscarinic M 2 receptor density is accompanied by a decrease in negative inotropic effects.