THE RESPONSE OF THE SMOOTH MUSCLE OF THE GALL BLADDER AT VARIOUS INTRAVESICAL PRESSURES TO CHOLECYSTOKININ

Abstract

The tension developed by the gall bladder when it contracts in response to a single submaximal dose of cholecystokinin depends on the initial pressure. The optimal intragall-bladder pressure for an optimal contraction in response to a submaximal dose of the hormone was found to vary from 4 to 5.5 cm. of pressure (Sollmann-Rademaeker''s soln.) in the isolated vesicle of the guinea pig and from 5 to 15 cm. of bile pressure in the dog''s vesicle in situ. When the pressure is optimal the vesical contracts more quickly than otherwise. The guinea pig''s gall bladder failed to contract in response to the standard dose of the hormone when intravesical pressure was 12.5 cm.; this value for the dog was 25 cm. At these high pressures a slight contraction was sometimes obtained when the standard submaximal dose of the hormone was increased from 2 to 4 times. If the gall bladder is "overstretched" by the relatively high pressure, then the viscus contracts less in response to the hormone. The range of optimal pressure for an optimal contraction is approximately the same as the optimal pressure for a tonus rhythm of optimal amplitude. This was found to be true of the isolated gall bladder of the guinea pig. If the gall bladder of the dog is subjected to a pressure of 30 or 40 cm. of bile for 2 hrs., it contracts less to the same dose of cholecystokinin than it did before. These observations must be considered in the interpretation of the response of the gall bladder to a meal.