Demostration of collaterization of the abdominal vagus in the rat using the double flourescent dyes technique [abstract]

ABSTRACT

Since the earlier report of Mitchel (1935), the central origin of preganglionic parasympathetic fibres has been studied by various investigators using different techniques and animal species. While it is now generally accepted that the dorsal motor nucleus of the vagus nerve (DMNV) is the principal source of preganglionic parasympathetic fibres to several organs in the thorax and abdomen, there has been persistent controversy as regards topographic representation of these organs in the DMNV. In a previous study in the ferret using the Horseradish peroxidase technique, some degree of topographic representation of the subdiaphragmatic part of the gastrointestinal tract was observed. It was, however, noted that no part of this nucleus is exclusively responsible for innervation of any segment of the gut. The author went on to speculate that the pattern of representation of the gut demostrated in the study might supply more than one segment of the gut by collaterization. The present study was thus designed to test this hypothesis. A total of 16 male and female Sprague Dawley rats weight range from 350 to 500g were used for the study. Four of these rats were used as control while the remaining 12 were used as experimental rats. Eight rats were injected with 1æ1 of 5 percent Diamidino yellow (DY) by multiple penetrations into the walls of the stomach while the same quantity and percentage of Fast blue (FB) was injected in the same manner into the walls of the duodenum and upper jejunum in the eight rats. Two rats had multiple injections of 1æ1 of 5 percent DY into the walls of the stomach only and two other rats had multiple injections of 1æ1 of 5 percent FB into the walls of the duodenum and upper jejunum only. Four control rats were injected with 1æ1 of normal saline (2 in the stomach and 2 in the intestine) in the same manner in which the experimental rats were injected. Each rat was anaesthetized with pentobarbitone and then perfused transcardially 14 days after the injections. Serial sections of the medulla were cut at 20-micron thickness with the cryosat and the sections examined with a Nikon Apaphot flourescence microscope. The result of the experiment revealed that in 8 rats injected with DY and FB some cells of the DMNV were labelled with DY only, some with FB only and some were doubly labelled with FB and DY. The two rats injected with FB showed FB labelled cells only while the two injected with DY showed DY labelled cells only. (AU)