Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio 45267, USA.
J Neurosci. 2011 Apr 13;31(15):5841-6. doi: 10.1523/JNEUROSCI.5680-10.2011.
Olfaction is an integral part of feeding providing predictive cues that anticipate ingestion. Although olfactory function is modulated by factors such as prolonged fasting, the underlying neural mechanisms remain poorly understood. We recently identified ghrelin receptors in olfactory circuits in the brain. We therefore investigated the role of the appetite-stimulating hormone ghrelin in olfactory processing in rodents and humans, testing the hypothesis that ghrelin lowers olfactory detection thresholds and enhances exploratory sniffing, both being related to food seeking. In rats, intracerebroventricular ghrelin decreased odor detection thresholds and increased sniffing frequency. In humans, systemic ghrelin infusions significantly enhanced sniff magnitudes in response to both food and nonfood odorants and air in comparison to control saline infusions but did not affect the pleasantness ratings of odors. This is consistent with a specific effect on odor detection and not the hedonic value of odors. Collectively, our findings indicate that ghrelin stimulates exploratory sniffing and increases olfactory sensitivity, presumably enhancing the ability to locate, identify, and select foods. This novel role is consistent with ghrelin's overall function as a signal amplifier at the molecular interface between environmental and nutritional cues and neuroendocrine circuits controlling energy homeostasis.
嗅觉是进食的一个组成部分，提供了预期摄入的预测线索。尽管嗅觉功能受到长时间禁食等因素的调节，但潜在的神经机制仍知之甚少。我们最近在大脑的嗅觉回路中发现了生长激素释放肽受体。因此，我们在啮齿动物和人类中研究了食欲刺激激素生长激素释放肽在嗅觉处理中的作用，检验了生长激素释放肽降低嗅觉检测阈值并增强探索性嗅探的假设，这两者都与寻找食物有关。在大鼠中，脑室内给予生长激素释放肽可降低气味检测阈值并增加嗅探频率。在人类中，与对照盐溶液输注相比，全身给予生长激素释放肽可显著增强对食物和非食物气味剂以及空气的嗅探幅度，但不会影响气味的愉悦度评分。这与对气味检测的特定影响而不是气味的享乐价值一致。总的来说，我们的发现表明，生长激素释放肽刺激探索性嗅探并提高嗅觉敏感性，可能增强寻找、识别和选择食物的能力。这种新的作用与生长激素释放肽作为环境和营养线索与控制能量平衡的神经内分泌回路之间分子界面的信号放大器的整体功能一致。
