AJP - Gastrointestinal and Liver Physiology, Vol 238, Issue 1 40-G44, Copyright © 1980 by American Physiological Society
Effects of sodium nitroprusside and verapamil on lower esophageal sphincter
R. K. Goyal and S. Rattan
Infusions of verapamil (V) and sodium nitroprusside (NP) caused
dose-dependent reductions in the lower esophageal sphincter pressure (LESP)
in anesthetized opossums. Verapamil caused a gradual fall during the
infusion and a gradual recovery upon cessation of the infusion. On the
other hand, NP caused a prompt reduction and a prompt recovery. Both the
agents also caused a fall in arterial blood pressure, but the fall in LESP
was not related to the fall in the blood pressure. Both the agents
antagonized the tonic and the phasic components of the LESP and, in large
doses, both drugs almost abolished the LESP. Esophageal contractions were
also antagonized by both agents, although verapamil was more effective than
nitroprusside in this regard. These studies show that phasic and tonic
components of LESP are not related to distinctive verapamil and
nitroprusside sensitive calcium activation systems. Moreover, the V- and
NP-sensitive calcium activation systems may lie in series rather than
parallel.
