e before, were added before a particular EFS train was used to study parasympathetic cholinergic innervation. Exogenous addition of 10 mM capsaicin, a compromise according to two former studies, was used to study eNANC innervation. The influence of TRP channels on eNANC responses of guinea pig PCLS was examined by the use of 10 mM ruthenium red or 30 mM SKF96365. Chemicals Atropine, capsaicin, magnesium sulphate, methacholine, neostigmine, Ruthenium red, SKF96365 propoxy]-4-methoxyphenethyl)-1H-imidazole) and standard laboratory chemicals were purchased from Sigma. Substances for cell culture were obtained from PAA laboratories. Neuronally Airway Control in Different Mammals Statistics Non-linear regression and statistical analyses were performed using GraphPad Prism 5 or JMP 9. Homoscedasticity was checked by the Bartlett test. If variances were unequal, unpaired data were either compared by the Mann-Whitney test or the Steel-Dwass test; if variances were equal by the t-test or analysis of variance followed by the Tukey test. Paired data were analyzed by the paired t-test. The statistical test used is indicated in the legends of the table and figures. The median effective frequencies were calculated by four parameter logistic regression and compared by the F-test. P,0.05 was always considered significant. Results Airway responses to EFS differed largely between species. Airways in PCLS from guinea pigs, sheep and humans contracted at maximum by about 4060% and did not revert to the initial area during the one minute interval before the next electric impulse was applied. However, airways in sheep PCLS revert completely, if recovery phase between stimulations is prolonged. PCLS from rats and marmoset contracted reversibly by about 20%. Marmoset airways also showed a unique behaviour in that contraction was followed by relaxation that exceeded the original airway caliber. Airways from mice did not respond in the range of the EFS conditions studied here. Since the mouse is such a common laboratory animal, we examined whether neural activation is possible at all in mouse PCLS by using harsher EFS conditions. In fact, the application of substantially higher frequencies or pulse durations led to airway contractions also in mouse PCLS. These were blocked by magnesium indicating that the responses were still of neural origin even at these harsher conditions. Neuronally Airway Control in Different Mammals The mouse example demonstrated how species-dependent neuronal excitability may be. Therefore, to further 10083-24-6 site compare the neuronal excitability of the other species, frequency response curves were conducted. Analyzing the frequency response curves for the half-maximal response revealed the following order of species sensitivity to EFS: sheep .guinea pig = human.rat. The EF50 values for humans and guinea pigs did not differ statistically. The EF50 of marmoset was 22.863.6 Hz, but the frequency response curve neglects the relaxant response and therefore the EF50 appears higher than without relaxation. To show that the EFS-induced airway contractions were of neural origin, we repeated the experiments in the presence of magnesium that competes with neural calcium channels and thus prevents neural responses. On the other hand, magnesium does not act directly on smooth muscle cells. Accordingly, EFS performed in the presence of 10 mM magnesium inhibited airway reactions in all species, but did not alter responses to exogenously added methacholine demonstr