| Summary: | 碩士 === 國立臺灣大學 === 動物學研究研究所 === 93 === Functional magnetic resonance imaging (fMRI) is an important tool for exploring brain activities. A stable anesthetized animal preparation is critically important for fMRI applications. The present study intended to determine the optimal infusion rate of α-chloralose anesthesia, the most popular anesthetics used in animal fMRI. In addition, the analgesia effect of morphine was tested by giving morphine before electrical stimulation. Long-Evans female rats (220 ~ 320 g) were used. After halothane induction, α-chloralose was given in an intravenous bolus injection (80 mg/kg). Subsequently, 3 different maintenance dosages were compared. These were administrated through intravenous infusion：high (60 mg/kg/hr), low (30 mg/kg/hr) or vehicle. During the 5 hours of recording period, blood pressure, heart rate, O2 and CO2 concentration in arterial blood were monitored. In addition, somatosensory evoked potentials (EEG) and flexor reflex activities (EMG) after hind paw electrical stimulation (2 mA, 0.5 ms, 0.3 Hz) were recorded every half hour. Under suitable infusion rate (30 mg/kg/hr), the physiological conditions remained stable for 5 hr, while the results suggested that the high dose and vehicle were not appropriate dosages for a stable anesthesia. Also, fMRI activations of the contralateral primary somatosensory cortex (SI) were readily observed under low dosage of α-chloralose infusion. In the morphine effect study, activations of anterior cingulate cortex (ACC), motor area/cingulate cortex (CC) and SI were attenuated after morphine administration. However, BOLD signals of SI were recovered after 3 hours, while the responses in ACC, motor area/CC remained suppressed. This study demonstrates that a steady α-chloralose anesthesia can be achieved for fMRI study, which can be utilized in the study of drug, lesion or other brain experiments.
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