[Static and dynamic responses of mechanoreceptors within gastric wall to intragastric pressure changes]

Adult cats were used under sodium pentobarbital anesthesia in order to investigate static and dynamic responses of mechanoreceptors within gastric wall to intragastric pressure changes caused by air inflation of the stomach. By means of tungsten microelectrodes, 17 afferent activities in response to gastric inflation were recorded from cervical vagal nerve trunk. Two modes of gastric inflation were applied (a) intermittent type for studying static response and (b) staircase one for studying dynamic response. The following results were obtained: Static response: An exponential relation was observed between intragastric pressure and frequency of gastric afferent activity, so maximal estimated frequency (fmax) and pressure constant could be calculated using method of extrapolation and method of least squares. Pressure constant is defined as an intragastric pressure at which frequency response is about 63% of fmax. Only one peak was seen in histogram of pressure constants of 17 afferent activities. Their average mean was 24 +/- 3 cmH2O. Dynamic response: A linear relation was observed between dynamic index and rate of pressure change. Dynamic index is defined as the net increment of frequency on dynamic phase of gastric inflation obtained by the difference between the maximal frequency and the frequency at three seconds after dynamic inflation. Dynamic constant which is considered to indicate the sensitivity of the receptor is defined by the slope of the regression line of dynamic index and rate of pressure change. Histogram of dynamic constant revealed two peaks, the large one with a mean of 10.2 +/- 4.0 imp divided by s/cmH2O divided by s and the small one with a mean of 2.5 +/- 0.5 imp divided by s/cmH2O divided by s.