Resumen de Vagal innervation of the rat intestinal apparatus. A new quantitative approach on the basis of the tracer-fluorescence-intensity.
In this methodological study, the effects of several parameters on the results of injections of a retrograde neurotracer into the gut were examined. To investigate the effects of tracer volume and the point of injection on the distribution, localisation and fluorescence of labelled cells in the dorsal motor nucleus of the vagus (DMN) after re t rograde tracer transport, Fluoro-Gold was injected into the gut of male Wistar rats. The tracer was injected into the wall of the intestine (cecum or anterior wall of the stomach corpus) of six rats; a control group of six rats received intraperitoneal application of the tracer. The tracer volume was varied. Neuro n a l labelling in the dorsal motor nucleus of the vagus was digitised under standardised conditions by means of software for measuring fluorescence and evaluated with data processing programs. The number of labelled cells, the location of labelled cells in the dorsal motor nucleus of the vagus, and the fluorescence of the individual labelled cells were examined. The control group was utilised to determine the degree of tracer diffusion into the peritoneal cavity after intramural tracer injection. After injection of a high tracer dose in a low concentrated solution into the cecum, a significant degree of tracer diffusion was detected. A reduction in the tracer dose resulted in a reduced number of labelled cells. In these cases, tracer diffusion can be excluded due to the small number of labelled cells. Injection of a small tracer dose into the anterior wall of the body of the stomach resulted in more labelled cells in comparison to the injection of an identical tracer dose into the cecum. In these cases no diffusion seemed to have occurred. Evaluation of the fluorescence intensity of the labelled cells showed that the two cells with the highest fluorescence intensity of each individual rat were localised in the lateral area of the dorsal motor nucleus of the vagus after tracer injection in the cecum, and in the medial area of the left side of the dorsal motor nucleus of the vagus after tracer injection into the anterior wall of the stomach body. When compared to the results of other investigators, these results are confirmed. The use of a limited tracer volume and restricted survival periods seems to allow for correct vagus projection by this method. So far this correlation has not been examined for other tracers.
