Figure 1.

The effects of electrical field stimulation (EFS) in circular muscle of ascending and descending colon from adult (35 to 60 years) and elderly (≥70 years) patients. Panel A shows representative trace examples illustrating responses during and after termination of EFS over a range of frequencies of stimulation. EFS was applied at 1–20 Hz and at 50 V for 10 s every 1 min. Using tissues from the adult group, panel B shows the overall contraction force (mean±SEM g tension/g wet weight of tissue) generated during EFS in both regions of colon for each frequency of stimulation in the presence of vehicle, tetrodotoxin (TTX) 1 µM, atropine 1 µM or L-NAME (N_ω-nitro-L-arginine methyl ester hydrochloride) 300 µM (n=5 each). Panels C and D show responses to EFS at 5 Hz, 50 V for 10 s, repeated every 1 min. The individual trace in panel C illustrates the ability of TTX 1 µM to inhibit responses evoked by repeated EFS. In panel D, the effects of single bursts of EFS are shown before and after treatment with atropine 1 µM or L-NAME 300 µM, in two muscle strips cut from the same tissue (male, 74, descending colon). The 10 s period of EFS is indicated by the horizontal bars (note the expanded time scale relative to panel C). Atropine inhibited contractions during EFS and decreased after-contractions. L-NAME inhibited relaxations during EFS and facilitated contraction amplitudes.