| Summary: | 碩士 === 國立臺灣大學 === 動物學研究研究所 === 94 === Sympathetic nerve activity (SNA) is important in regulation of cardiovascular functions. Slow oscillations in blood pressure fluctuation is highly correlated with SNA fluctuation of the same frequency, and some studies suggest that this slow rhythms reflect the sympathetic modulation of resistance vessels. However, the frequency components and the origin of sympathetic rhythms at 0~1 Hz is still not clear. Therefore, two objectives of this study is to figure out the frequency components of sympathetic oscillations at 0~1 Hz and to determine whether different RVLM neurons, which are critically important in the generation of the sympathetic rhythms, contributed to specific frequencies in SNA. Blood pressure and renal SNA were recorded simultaneously in awaked rats. Group- average spectra of SNA in 7 rats showed that spectral power both in the very low frequency(VLF) range and low frequency(LF) range were prominent in sympathetic rhythms at 0~1 Hz. In addition, the second experiment was performed. Blood pressure, renal SNA and neuronal activity in RVLM were recorded simultaneously in anesthetized, paralyzed and artificially ventilated rats. We found 85 RVLM neurons recorded. Neuronal activity changed in response to increased blood pressure were used to classify RVLM neurons into three groups, including negatively response with blood pressure (BP(-) neurons), positively response with blood pressure (BP(+) neurons) and no response with blood pressure (control). According to coherence analysis, BP(-) may provide the major contribution to all three frequency bands in the sympathetic rhythms. Among them, neurons which contributed to LF range and HF range excited SNA while these neurons were firing. These results show that there may be separate functional group in the RVLM, but only one group of neurons that were modulated by baroreflex contribute to both VLF and LF rhythms in SNA.
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