达乌尔黄鼠犁鼻器和副嗅球的组织结构及嗅球c-Fos表达的季节变化

啮齿动物的犁鼻器和副嗅球与社会通讯和生殖行为有关，主嗅球影响其觅食行为。达乌尔黄鼠（Spermophilus dauricus）是一种具有较低社会行为的储脂类冬眠动物。本研究用组织学和免疫组织化学方法探究了其犁鼻器和副嗅球的结构特点及嗅球神经元活动对季节变化的适应。结果发现，达乌尔黄鼠犁鼻器具有较大的血管，犁鼻器管腔外侧为非感觉性的呼吸上皮（Respiratory epithelium，RE），内侧为感觉上皮（Sensory epithelium，SE），RE较SE薄，靠近管腔处为假复层柱状上皮。选取犁鼻器中间部位比较，发现SE的厚度、长度及感觉细胞密度均无性别差异。副嗅球位于主嗅球后方背内侧，由6层细胞构成。侧嗅束穿过副嗅球，位于颗粒细胞层之上。雄性达乌尔黄鼠较雌性有更长的僧帽细胞层和颗粒细胞层。春季（3月）和冬季（1月）达乌尔黄鼠主嗅球的嗅小球层、僧帽细胞层和颗粒细胞层的c-Fos-ir神经元密度显著低于夏季（7月）和秋季（10月），且冬季外网织层的c-Fos-ir神经元密度显著低于夏季和秋季，说明达乌尔黄鼠在冬季和春季的嗅觉神经活动较弱，呈现出对冬眠的生理性适应。这些结果丰富了动物犁鼻器和副嗅球的形态学资料，并有助于理解冬眠动物嗅觉系统对季节变化和冬眠的适应。

Histological structure of the vomeronasal organ and accessory olfactory bulb and the seasonal changes of olfactory bulb c-Fos expression in Spermophilus dauricus

The vomeronasal organ (VNO) and the accessory olfactory bulb (AOB) in rodents are related to social communication and reproductive behavior, while the main olfactory bulb (MOB) influences foraging behavior. The Daurian ground squirrel (Spermophilus dauricus) is a typical fat-storing hibernator that exhibits low levels of social behaviors. Using histological and immunohistochemical methods, this study has investigated the detailed histological features of the VNO and AOB in the Daurian ground squirrels and how the neuronal activation of the MOB responds to the seasonal variations. There is a large vomeronasal blood vessel in the VNO of the Daurian ground squirrel. The lumen of the VNO is lined laterally by a non-sensory respiratory epithelium (RE) and medially by the sensory epithelium (SE). The RE is thinner than that of the SE, and it consists of pseudostratified columnar epithelium near the lumen. At the middle region of the VNO, no sex differences are observed in either the height or length of the SE, nor in the density of the receptor cells. The AOB is located caudal and dorso-medially relative to the position of the MOB. The AOB strata consist of six layers of cells. The lateral olfactory tract (LOT) passes through the AOB and is positioned above the granule cell layer (GCL). The mitral cell layer (MCL) and GCL in males are longer than that in females. The densities of c-Fos-ir neurons of the glomerular layer (GL), MCL, and GCL in spring (March) and winter (January) are less than that in summer (July) and autumn (October). Furthermore, the external plexiform layer (EPL) displays fewer c-Fos-ir neurons in winter than that in summer and autumn. These results indicate that the olfactory bulb of the Daurian ground squirrel exhibits much weaker neuronal activation in winter and spring, showing a physiological adaptation to hibernation. The present study adds to the body of morphological knowledge on the VNO and AOB and furthers our understanding of the specific acclimatization of the olfactory system to seasonal variation and hibernation in hibernating rodents.