AJP - Gastrointestinal and Liver Physiology, Vol 254, Issue 2 254-G263, Copyright © 1988 by American Physiological Society
Comparison of gastrointestinal responses to CCK-8 and associated with vomiting
I. M. Lang, J. Marvig and S. K. Sarna
Department of Surgery, Medical College of Wisconsin, Milwaukee.
The gastrointestinal motor and myoelectric responses associated with
vomiting induced by apomorphine (APO) and activated by cholecystokinin
octapeptide (CCK-8) were compared as well as the mechanisms of initiation
of these responses. Twelve dogs were surgically implanted with strain-gauge
force transducers or bipolar electrodes for chronic recording of
contractile or electrical activity. The responses to CCK-8 were determined
in the fasted state and compared with the gastrointestinal motor and
myoelectric correlates of vomiting activated by APO. After recording
control responses, the effects of the following agents on these responses
were determined: atropine, domperidone, and proglumide. In addition, the
effects of supradiaphragmatic vagotomy or splanchnicectomy were determined.
We found that CCK-8 activated contractile and myoelectric responses in the
absence of vomiting, which were similar in most respects to those found in
association with vomiting. These responses included 1) the retrograde giant
contraction (RGC) and 2) the post-RGC phasic contractions. These RGCs were
similar with respect to their activation in an all-or-none fashion,
magnitude, duration, and position in the small intestine. The myoelectric
correlates of these motor responses were similar qualitatively and
quantitatively. The responses activated by APO and CCK-8 differed with
respect to their coordination at different levels of the gastrointestinal
tract. Whether activated by CCK-8 or APO, atropine blocked the RGC but not
the post-RGC contractions. Domperidone blocked all responses to APO but not
to CCK-8, and splanchnicectomy did not affect responses to either agent.
Vagotomy blocked all gastrointestinal responses to APO but not to CCK-8.
These results indicated that CCK-8 activates the gastrointestinal motor and
myoelectric correlates of vomiting by a peripheral mechanism that does not
include dopamine receptors.
