Figure 5.

Effect of nifedipine on slow waves (SWs) and contractile activity in the dog and monkey rectoanal region. (A) Sample traces of SWs recorded from the dog internal anal sphincter (IAS) under control conditions (left trace) and at 8 minutes and 15 minutes following addition of nifedipine (middle and right traces). Nifedipine completely abolished SWs after 15 minutes. (B) Sample traces of SWs recorded from the submucosal side of the circular muscle in the dog rectum under control conditions (left trace) and at 5 minutes and 20 minutes following addition of nifedipine (middle and right traces). SWs were not abolished by nifedipine but upstroke velocity and duration were decreased. (A) and (B) are adapted from Mutafova-Yambolieva et al³³ with permission. Sample traces of the contractile activity recorded from the monkey IAS (C) and rectum (D) before and after addition of nifedipine. Dotted line indicates zero active contraction. Contractile activity in the IAS consisted of phasic contractions superimposed upon tone. Inset shows phasic contractions at a faster sweep speed (C). Contractile activity in the rectum was predominantly phasic (D). Nifedipine abolished tone and phasic contractions in both muscles (C, D).