Figure 5.

Age-dependent changes in cholinergic and nitrergic responses to electrical field stimulation (EFS) in human ascending and descending colon. EFS was applied at 5 Hz and at 50 V for 10 s every 1 min, in the absence and presence of N_ω-nitro-L-arginine methyl ester hydrochloride (L-NAME) 300 µM or atropine 1 µM. Panels A and D show examples of original traces showing the effects of, respectively, L-NAME and atropine in the adult and elderly ascending colon. Similarly, panels B and E show examples of original traces for both treatments in the adult and elderly descending colon. Panels C and F show the data for each treatment in each region of adult (35–60 years of age; □) and elderly (≥70 years; ■) colon, for each tissue tested. The data are expressed as g tension/g wet weight of tissue, generated during and after termination of EFS, together with the mean±SEM contractile force. Respectively, n=14/6 and 7/4 (response generated during/after termination of EFS in the presence of L-NAME and atropine for adult ascending colon), 25/6 and 14/6 (elderly ascending colon), 16/8 and 14/8 (adult descending colon) and 23/5 and 15/5 (elderly descending colon); note that after-contractions did not always occur so their n values are smaller than for the responses measured during EFS. These were analysed using analysis of variance with Sidak’s multiple comparison tests; *P<0.05 only where indicated.