By reducing the cerebral blood flow and thereby increasing the resting deoxyhaemoglobin concentration, many human studies have shown that caffeine has a beneficial effect on enhancing the magnitude of blood‐oxygenation‐level‐dependent (BOLD) responses. However, the effect of caffeine on BOLD responses in animals under anaesthesia has not been demonstrated. In this study, we aimed to determine the effect of systemic caffeine administration on BOLD responses in rats under alpha‐chloralose. By applying electric whisker pad stimulation to male Sprague‐Dawley rats, we performed fMRI measurements before and after the caffeine injection (40 mg/kg, n = 7) or an equivalent volume of saline (n = 6) at 7T. To understand the potential perturbation of animal physiology during stimulation, arterial blood pressure was measured in a separate group of animals (n = 3) outside the scanner. Caffeine significantly decreased baseline BOLD signals (p = .05) due to the increased deoxyhaemoglobin level. Both BOLD responses and t‐values in the primary somatosensory cortex were significantly increased (both p < .05). The blood pressure changed insignificantly (p > .05). No significant differences in BOLD responses and t‐values were observed in the control condition of saline injection (both p > .05). These findings suggested that, although the cerebral activity was lower under alpha‐chloralose anaesthesia, the higher level of deoxygemoglobin at the baseline under the caffeinated condition can benefit the magnitude of BOLD responses in rats. These findings suggest that animal models might serve as potential platforms for further caffeine‐related fMRI research studies.

中文翻译：

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咖啡因增强α-氯代海洛因麻醉期间大鼠对电须垫刺激的大胆反应

通过减少脑血流量从而增加静息的脱氧血红蛋白浓度，许多人体研究表明，咖啡因对增强血氧水平依赖性（BOLD）反应的强度具有有益作用。但是，尚未证明咖啡因对麻醉动物中BOLD反应的影响。在这项研究中，我们旨在确定全身性咖啡因对α-氯藻糖对大鼠大胆反应的影响。通过对雄性Sprague-Dawley大鼠进行电晶须垫刺激，我们在咖啡因注射（40 mg / kg，n  = 7）或等量生理盐水（n = 6）在7T。为了了解刺激过程中动物生理的潜在扰动， 在扫描仪外部的另一组动物（n = 3）中测量了动脉血压。 由于增加的脱氧血红蛋白水平，咖啡因显着降低了基线BOLD信号（p = .05）。初级体感皮层的BOLD响应和t值均显着增加（均为p  <.05）。血压变化不明显（p  > .05）。在生理盐水注射的对照条件下，BOLD反应和t值均无显着差异（均p > .05）。这些发现表明，尽管在α-氯代海洛因麻醉下大脑活动降低，但是在咖啡因条件下，基线时较高的脱氧血红蛋白水平可有益于大鼠的BOLD反应幅度。这些发现表明，动物模型可能会成为进一步开展咖啡因相关的功能磁共振成像研究的潜在平台。