Effects of 1 μm atropine on the peak amplitude of near-maximum amplitude ion currents induced by 1 mm ACh and on small (<10% of Imax) ion currents induced by 1 μm ACh for various subunit combinations of neuronal nAChRs
| nAChR | 1 mm ACh response | 1 μm ACh response | p1-a |
|---|---|---|---|
| % | |||
| α2β2 | 85.9 ± 7.8 (6) | N.D.1-b | |
| α2β4 | 51.0 ± 3.0 (6) | 93.5 ± 2.8 (6) | < 0.001 |
| α3β2 | 85.9 ± 3.7 (10) | 91.0 ± 4.6 (6) | 0.03 |
| α3β4 | 87.5 ± 4.7 (6) | 88.3 ± 4.3 (6)1-c | 0.76 |
| α4β2 | 74.1 ± 7.2 (7) | 140.5 ± 4.9 (6) | < 0.001 |
| α4β4 | 43.5 ± 4.5 (6) | 170.3 ± 10.2 (6) | < 0.001 |
| α7 | 53.3 ± 4.8 (6) | 81.9 ± 3.5 (4)1-c | < 0.001 |
All currents were recorded at −80 mV, and the percent response was obtained by normalizing the peak amplitude in the presence of atropine to the peak amplitude of control responses evoked by the same concentration of ACh. Values represent mean ± standard deviation measured for the number of oocytes (n). For each subunit combination, results were obtained from oocytes of three to five frogs (left) and of two frogs (right). All effects of atropine were statistically significant with respect to control values (paired t tests; p < 0.007).
↵1-a Student’s t test probability of the hypothesis that the effect of atropine on responses evoked by high agonist concentration (left column) equals the effect on responses evoked by low agonist concentration (right column).
↵1-b Not determined because large numbers of receptors were not expressed.
↵1-c Inward currents induced with 10 μm ACh.