Impact of group housing quantity and quality on the stress-induced decreases in the number of dentate newly proliferated cells and neuroblasts

• Main Authors: Li-HanSun, 孫莉涵
• Other Authors: Lung Yu
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/9s8ss9

碩士 === 國立成功大學 === 生理學研究所 === 106 === To obtain various forms of social support is critical for maintaining individual’s psychological and physical well-being. Social interaction impairments have been frequently associated with decreased quality of life and psychopathological states. Previously, we have reported that the presence of three conspecifics prevents contact-involving stressors-induced decreases in newly proliferated cell and neuroblast in mouse hippocampal dentate gyrus (DG). This study was designed to determine whether physical interaction, number of conspecifics, and conspecifics’ physiological status were important in the emergence of these stress-buffering effects. To avoid physical interaction, here a 1-hr contact-free stressor regiment consisting of restraint in water was used. Although the unconditioned footshock stressor was smitted, the contact-free single stressor regimen induced comparable decreases in DG cell proliferation and early neurogenesis as compared to the original compound stressors. In this regard, the presence of one saline-, oxytocin (OT)-pretreated, or three lipopolysaccharide (LPS)-pretreated conspecifics and cotton tip-impregnated with OT were assessed for the buffering effects. We found that presentation of three intact and LPS-pretreated conspecifics prevented the stressor-induced decreases in the number of newly proliferated cell and neuroblast in hippocampal DG, while three conspecifics did not affect the stressor-stimulated corticosterone (CORT) elevations. Presentation of one saline- or OT (1 mg/kg)-pretreated conspecific did not exert observable stress-buffering effects. Airborne OT was found to prevent the stressor-induced decreases in DG cell proliferation and early neurogenesis, while pretreatment with a selective peripheral OT receptor antagonist, L-371,257, abolished such OT-produced buffering effects, no matter using intraperitoneal injection or nasal cavity lavage. These findings, taken together, suggest that conspecifics’ physical interaction and sickness play a minor role in mediating the conspecifics’ buffering effects on stress-induced decreases in cell proliferation, early neurogenesis or stress-provoked CORT secretion. Moreover, stress-buffering effects are eminent with the presence of three conspecifics but negligible with presentation of one. Finally, airborne OT produces stress-buffering effects in this regard possibly via its stimulation on peripheral OT receptors. OT merits further study to substitute for companions’ stress-buffering effects in this regard.