Table 2.

Pharmacology of responses to EFS in circular muscle from human adult ascending and descending colon

Drug	Response	Adult ascending		Adult descending
		During EFS (g/g tension)	After EFS (g/g tension)	During EFS (g/g tension)	After EFS (g/g tension)
Atropine 1 µM	Contraction prevented during EFS, revealing or enhancing relaxation; contractions after EFS attenuated	−2.6±1.0 (6)	−1.8±0.8 (4)	−1.7±0.6 (8)	−1.8±0.5 (8)
Atropine plus NK1–3 antagonists	As above but with consistent inhibition of contractions after EFS	−4.4±2.1 (5)	−1.5±0.5 (3)	−0.7±0.4 (4)	−4.1±1.9 (3)
L-NAME 300 µM	Contraction during EFS increased in ascending colon only; no consistent effect on contractions after EFS	3.2±1.1 (14)	−0.2±1.2 (7)	0.8±0.5 (16)	0.8±0.7(14)
MRS2500 1 µM	No consistent change during and after EFS	0.8±0.5 (5)	0.1±0.3 (3)	0.3±0.1 (4)	−2.3±1.0 (3)

EFS was applied at 5 Hz, 50 V for 10 s, repeated every 1 min. The effects of treatment with atropine, NK_1,2,3 receptor antagonists (L732138 1 µM, GR 159897 0.1 µM and SB-235375 0.1 µM, applied together and in the presence of atropine), L-NAME and MRS2500 are shown for the responses during and after EFS. Data are given as the decrease or increase in mean±SEM of the overall muscle tension during each phase of EFS, expressed as g tension/g wet weight of tissue. The n values (in parenthesis) refer to numbers of patients; since after-contractions were not consistently observed in tissues from all patients, these were sometimes smaller.

EFS, electrical field stimulation; L-NAME, N_ω-nitro-L-arginine methyl ester hydrochloride.