Study On The Vomeronasal System Of Gansu Zokor (Myospalax Cansus) And Root Vole (Microtus Oeconomus)

Gansu zokor (Myospalax cansus) is a solitary, territorial and aggressive subterranean rodent. It lives in individual tunnel systems, rarely encountering each other except during the mating season. It shows the most striking behavioral and physiological adaptation to underground life. In order to compare the accessory olfactory bulb and vomeronasal organ between subterranean rodent and surface dwell rodent as well as the function in their life history, the histological and immunohistochemistrical methods were used to study the structure of accessory olfactory bulb and vomeronasal organ in Gansu zokor (Myospalax cansus) and root vole (Microtus oeconomus), and the c-Fos expression and its distribution in the vomeronasal system projects regions in the Gansu zokor brain were also determined. The main results are as follows:1. The structure of accessory olfactory bulb and vomeronasal organ of Gansu zokor are similar to the root vole. Vomeronasal epidermis is in the inboard wall of vomeronasal tube, while outside wall protrudes to the central cave slightly, which is pseudostratified epithelium, and its base is bone marrow of a triangle. The vomeronasal tube opens into the nasal cavity directly. In its rostral portion, it had a lateral flattened shape, but caudally the organ exhibited a typical crescent shape and a greater size. The organ is rotated along its longitudinal axis. The location of the vomeronasal epidermis shifted from the basal vomeronasal tube to the lateral vomeronasal tube gradually. The location of the pseudostratified epithelium shifted from the lateral vomeronasal tube to top of the vomeronasal tube gradually. In its most caudal portion the organ decreased in size and ends in glandular branches. The microstructures of accessory olfactory bulb of Gansu zokor and root vole are composed of glomeruli layer, external plexiform layer, mitral cell layer, internal plexiform layer and granule cell layer.2. Accessory olfactory bulb and vomeronasal organ of Gansu zokor have sexually dimorphic. In Gansu zokor, the vomeronasal epidermis thickness in adult males, the zones width of accessory olfactory bulb granular cells and the mitral cells are remarkably wider than that of the females (P<0.05). But the length of vomeronasalmucous, the density of vomeronasal epidermis neuron cells, the diameter of neuron cell nucleus, the zones length of accessory olfactory bulb granular cells and the mitral cells in females and males are no significant difference (P>0.05). Compared with the root voles, the sexually dimorphic of accessory olfactory bulb and vomeronasal organ in Gansu zokor are obvious.3. Accessory olfactory bulb and vomeronasal organ of root vole is sexually dimorphic. The vomeronasal epidermis is thick in adult males of root vole. The zones length of accessory olfactory bulb granular cells are longer than the females (P<0.05). But the density of vomeronasal epidermis neuron cells, the zones length of accessory olfactory bulb mitral cells, the density of accessory olfactory bulb mitral cells, the zones width of accessory olfactory bulb granular cells and the mitral cells in females and males are no significant difference (P>0.05).4. The vomeronasal epidermis thickness in Gansu zokor, the zones width of accessory olfactory bulb granular cells and the mitral cells are well developed than that of the root vole (P<0.05). So accessory olfactory bulb and vomeronasal organ of Gansu zokor are well developed than that of the root vole, and it take a important role in the mating and courtship activitise of the Gansu zokor.5. There is a certain corresponding relation between the accessory olfactory bulb and vomeronasal organ shape. The vomeronasal epidermis and accessory olfactory bulb of Gansu zokor are thick and short. The vomeronasal epidermis and the accessory olfactory bulb of root voles are thin and long. The cause of this kind of corresponding relation is there is nerve projection between these two structures.6. Stimulated by the unfamiliar homogeneous urine of Gansu zokor, the frequency to visite the stimulant origin of the male Gansu zokor is obviously higher than the female (P<0.05). The duration of sniffing/licking the sent origin is shorter than the female (p<0.05). It showed that the capcity to distingusih the unfamiliar homogeneous urine has a sex difference distingusih in Gansu zokor. Compared with the data on the root vole, ability distingusih to unfamiliar homogeneous urine in Gansu zokor is stronger than in root vole.7. Stimulated by the unfamiliar homogeneous urine of Gansu zokor, c-Fos-IR present in the accessory olfactory bulb granular cells and the mitral cells, main olfactory bulb granular cells and the mitral cells, bed nucleus of the stria terminalis (BST), ventromedial hypothalamic nucleus (VMH), medial preoptic area (MPO), medial...