Figure 3.

Concentration–response curves for the inhibition of the electrical field stimulation-evoked contractions of the guinea-pig myenteric plexus-longitudinal muscle (MPLM) by WIN 55,212-2 [(R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)-pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone mesylate] constructed in the absence and presence of physostigmine (eserine). The guinea-pig MPLM was subjected to single electrical pulses of 0.5 ms duration, 110% supramaximal voltage at a frequency of 0.05 and 0.1 Hz respectively. Each curve was fitted by non-linear regression analysis. Each symbol represents the mean value of inhibition of the contractions expressed as a percentage reduction of the amplitude of the contractions measured immediately before the addition of any drug to the organ bath. Vertical lines indicate SEM, n= 6 for each curve. Physostigmine was added 20 min before the first addition of WIN 55,212-2.