No abstract

In numerous animals, one essential chemosensory organ that detects chemical signals is the vomeronasal organ (VNO), which is involved in species-specific behaviors, including social and sexual behaviors. The purpose of this study is to investigate the mechanism underlying the processing of chemosensory cues in semi-aquatic mammals using muskrats as the animal model. Muskrat (Ondatra zibethicus) has a sensitive VNO system that activates seasonal breeding behaviors through receiving specific substances, including pheromones and hormones. Vomeronasal organ receptor type 1 (V1R) and type 2 (V2R) and estrogen receptor α and β (ERα and ERβ) were found in sensory epithelial cells, non-sensory epithelial cells and lamina propria cells of the female muskrats’ VNO. V2R and ERα mRNA levels in the VNO during the breeding period declined sharply, in comparison to those during the non-breeding period, while V1R and ERβ mRNA levels were detected reversely. Additionally, transcriptomic study in the VNO identified that differently expressed genes might be related to estrogen signal and metabolic pathways. These findings suggested that the seasonal structural and functional changes in the VNO of female muskrats with different reproductive status and estrogen was regulated through binding to ERα and ERβ in the female muskrats’ VNO.

Toll-Like Receptor 4 (TLR4) recruits the adaptor protein myeloid differentiation primary response gene 88 (MyD88) and Interleukin-1 Receptor-Associated Kinase 4 (IRAK4), triggering a series of immune responses. In this study, we investigated the localizations and expression levels of TLR4, MyD88 and IRAK4 in the skin of Rana dybowskii during the breeding and pre-hibernation periods. Histologically, the skin of Rana dybowskii consisted of epidermis and dermis. The epidermis consisted of stratum corneum, stratum granulosum, stratum spinosum and stratum germinativum, while the dermis was composed of homogenous gel, mucous glands and granular glands. TLR4, MyD88 and IRAK4 were immunolocalized in the epithelial and glandular cells of skin in both periods. Western blotting revealed that TLR4, MyD88 and IRAK4 were expressed in the breeding and pre-hibernation periods. Real-Time PCR showed that the mRNA expression level of MyD88 in the pre-hibernation decreased when compared with the breeding period, while the mRNA expression levels of TLR4 and IRAK4 were not significantly different between the breeding and pre-hibernation periods. These results suggested that TLR4, MyD88 and IRAK4 might participate in the skin immune system of Rana dybowskii during the breeding and pre-hibernation periods.