Vagal preganglionic neurons innervating the different gastric regions in the Japanese quail (Coturnix japonica)

The cytoarchitecture and distribution patterns of the vagal preganglionic neurons within the dorsal motor nucleus of the vagus nerve (DMNX) innervating the proventriculus and the gizzard of the Japanese quail were examined by Nissl staining and the horseradish peroxidase (HRP) method. A 30% solution of HRP was injected into nine different gastric regions: the ventral and dorsal parts of the proventriculus, the caudodorsal and cranioventral thick muscles, the craniodorsal and caudoventral thin muscles, and the pylorus, and the ventral and dorsal tendons of the gizzard. Nissl preparations showed that the DMNX is composed of two cell groups, the dorsal magnocellular and mediocellular subnucleus (Xd) and the ventral parvicellular subnucleus (Xv). After injection of HRP into the ventral and dorsal parts of the proventriculus, HRP-labeled cells were predominantly observed in the left and right DMNX, respectively. The rostrocaudal distribution patterns of HRP-labeled cells in the Xd and Xv were symmetric on the left and right sides. The distribution patterns of labeled cells following the injection of HRP into each region of the gizzard showed that there was very little difference in the number of neurons between the left and right DMNX, and no topographic localization was found in the Xd and Xv. The vagal preganglionic neurons projecting to the gizzard lay more caudal than the ones for the proventriculus. This study suggested topographic localization in the distribution patterns of the vagal preganglionic neurons innervating the proventriculus and the gizzard.