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 <25 years (mean age: 16.8±2.0 years, n=9) significantly larger than in patients aged 50–69 years (mean age: 62.5±0.7 years, n=33) and were further decreased in 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 M2 receptor density is accompanied by a decrease in negative inotropic effects.