早期聲音剌激對新生幼鼠發育之影響
環境多樣性對「關鍵期」動物發育的影響，過去有不少學者提出研究論文予以証明。曾經提出過的包括聲音剌激對大白鼠大腦皮質會產生空間重整(spatial rearrangement )及神經可塑性(neuronal plasticity)的變化。但是其中聲音剌激在新生動物的效應及機轉並不清楚，此研究目的在探討新生幼鼠在P1~P21，使用連續聲音刺激(4 kHz、65dB SPL、23:00 ~ 07:00 ) 對中腦神經及血管系統發育的影響。 實驗期間 (P1~P21)我們發現幼鼠的體重及母鼠的攝水量均呈現增加。實驗組神經反射(righting、cliff avoidance、negative geotaxis、auditory startle and vibrissa placing )及身體發育(eye opening、incisor eruption & ear unfolding)較對照組來得早。實驗組幼鼠下丘有較大之血管表面總面積，個數以及密度。使用正切(tangential section)與傳統冠狀切(coronal section)方法比較檢體，發現正切方式在下丘本體血管表面總面積，個數以及密度表現都比傳統方式來得好。此外利用正切方式比較 IC 低頻區及高頻區血管總面積、個數以及密度，低頻區有顯著的血管增加及輪廓改變的現象。意味血管增加及輪廓改變與音訊有著相關性。以血管灌注為導向的切片方式，較能符合研究非平面血管發展的需求。對於連續聲音剌激對中腦神經及血管系統發育的生物標誌物，我們利用相同實驗條件測量包括血管內皮生長因子(VEGF)，缺氧誘導因子-1α (HIF-1α)、突觸生長因子(synaptophysin) 以及 腦源性神經營養因子(BDNF)相關蛋白表現量以western blot以及ELISA 方式檢定。實驗組VEGF之 western blot以P8 時在IC表現較對照組為旺盛,在大腦皮質以P14較對照組為旺盛。此外實驗組IC synaptophysin 之 western blot 以P12、P14較對照組為高，並以P12為最高。 在大腦皮質對照組自第8天即較實驗組為高並在P14天為最高。 HIF-1α在所有組別中均無表現，可能與VEGF 出現沒有關聯性。ELISA 量測在IC看到BDNF在P8，P10，P12時較對照組高。ELISA 量測在大腦皮質看到VEGF及BDNF呈現P8及P14時較對照組大幅上揚的情形其中VEGF在P8更是上升近3倍。VEGF，synaptophysin及BDNF在實驗組較高的天數呈現上升可以指引日後對早期聲音剌激對新生幼鼠神經發育探討的進一步方向。

Effects of neonatal sound exposure on brain development
Effects of enriched environment during critical period have been discussed by varies scholars. These changes involved spatial rearrangement of cortical mapping and neuronal plasticity after sound exposure. However、effects of sound exposure during early postnatal period have not been investigated. This study focused on the neuronal and vascular changes at the auditory midbrain of neonatal rat pups after exposure to continuous tone (4 kHz、65dB SPL、23:00 pm ~ 07:00 am) during postnatal day one (P1) to postnatal day twenty-one (P21). Increased body and brain weights were recorded in exposure rat pups with simultaneous increase of water intake of the nursing mothers. Results showed earlier emergences of reflexes (righting、cliff avoidance、negative geotaxis、auditory startle and vibrissae placing) and body developments (incisor eruption、ear unfolding and eye opening) in exposed rat pups. Capillary changes in the inferior colliculus (IC) showed significant increase of vessels area、numbers & density in exposed rat pups. Sections from IC of rat pups were studied under two different angles (tangential vs. coronal) and micro vessel profiles compared after toluidine blue staining. Results showed that tangential sections produced higher counts in all three aspects of vessel profiles (surface area、density and round lumen counts). When comparing low frequency and high frequency laminas using tangential sections、significant increase of micro vessel profiles were noted in low frequency related zone. There is possibility of frequency related vascular remodeling at the low frequency area. Moreover、sectioning angle is critical in revealing microvasculature in the neural structures where arterial entry has an apparent anisotropic pattern. Biochemical markers for angiogenesis were investigated by harvesting tissues from the brain. Both the IC and the auditory cortex (AC) were studied、starting from P8 to P14 at two-days intervals. Tissues were examinated by western blotting and ELISA analysis. After sound exposure、we found higher VEGF in the IC on P8 but a higher VEGF in the AC on P14、as revealed by western blotting. For synaptophysin level at the IC、a gradual increase from P8 to P14 was found in exposed animals. The same pattern holds for synaptophysin expression at the AC of controls. There was no HIF-1α expression in any of our collected tissues suggesting no detectable correlation between VEGF and hypoxic drive in our animals. ELISA analysis for AC and IC showed higher concentration of VEGF and BDNF at P8 and P14 in exposed groups. For the IC、although BDNF showed higher concentrations at P8、P10 and P12 compared to controls、the differences were not statistically significant. Results showed a strong sound exposure effect in accelerating growth and development during the neonatal period as reflected in the emergence of reflexes、developmental landmarks and increase of microvasculature in the IC. Preliminary results on the neurochemical profiles were not conclusive in revealing the underlying mechanisms though VEGF、synaptophysin、and BDNF were likely involved.

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