Fig. 2

Longitudinal smooth muscle preparations of distal colon isolated from control animals or 6-OHDA rats at weeks 4 and 8. a Tissues were maintained in Krebs solution, containing L-NAME (100 μM), guanethidine (10 μM), atropine (1 μM), GR159897 (NK2 receptor antagonists, 1 μM), and SB218795 (NK3 receptor antagonists, 1 μM), and contractile responses were elicited by electrical stimulation (ES: 0.5 ms, 30 mA, 10 s, 1–20 Hz). Each column represents the mean ± S.E.M value obtained from eight experiments. *P < 0.05, significant difference vs control. Tracings in the inset on the top of each panel display contractile responses to ES recorded at a frequency of 10 Hz. b Tissues were maintained in standard Krebs solution containing tetrodotoxin (1 μM), and contractions were evoked by increasing concentration of exogenous substance P (SP, 0.001–10 μM). Tracings in the inset on the top of each panel display contractile responses to exogenous SP at a concentration of 10 μM. Each point represents the mean ± S.E.M value (n = 8). *P < 0.05, significant difference vs control