Stratford Jennifer M, Curtis Kathleen S, Contreras Robert J
Department of Psychology and Program in Neuroscience, The Florida State University, Tallahassee, FL 32306-1270, USA.
Physiol Behav. 2006 Oct 30;89(3):311-9. doi: 10.1016/j.physbeh.2006.06.009. Epub 2006 Sep 11.
Taste is intimately associated with food choice, yet little is known about the role of taste in preferences for dietary fat, a major component of many foods. We measured the taste threshold for linoleic acid (LA), an essential free fatty acid found in dietary fat, before and after bilateral transections of the chorda tympani nerve (CTX) in adult male and female rats. We conditioned a taste aversion to 88 microM LA and assessed the generalization of the aversion to lower LA concentrations to determine LA discrimination thresholds. We discovered that female rats had a lower LA discrimination threshold (approximately 2.75 microM LA) than did male rats (approximately 11 microM LA). In another set of animals, we performed CTX and found that CTX elevated LA threshold to the same level (approximately 22 microM LA) in male and female rats. Finally, we evaluated licking responses to 11, 22, 44 and 88 microM LA mixed in sucrose by male rats and ovariectomized (OVX) female rats treated with estradiol benzoate or oil vehicle. All rats increased licking to increasing LA concentrations, but OVX rats responded to a lower LA concentration (22 microM) than did males (44 microM) in 10-s trials. However, estradiol did not affect this outcome. Collectively, these experiments show that male and female rats use taste to discriminate LA and that the chorda tympani nerve, which innervates taste buds on the anterior tongue, plays a role in this discrimination. Furthermore, sex differences in fat preferences may depend on differences in fatty acid taste thresholds as well as on the taste stimuli with which fat is combined.
味觉与食物选择密切相关，但对于味觉在膳食脂肪（许多食物的主要成分）偏好中所起的作用却知之甚少。我们测量了成年雄性和雌性大鼠双侧鼓索神经（CTX）横断前后，膳食脂肪中一种必需游离脂肪酸——亚油酸（LA）的味觉阈值。我们对88微摩尔/升的LA进行味觉厌恶条件反射，并评估对较低LA浓度的厌恶泛化情况，以确定LA辨别阈值。我们发现，雌性大鼠的LA辨别阈值（约2.75微摩尔/升的LA）低于雄性大鼠（约11微摩尔/升的LA）。在另一组动物中，我们进行了CTX横断，发现CTX使雄性和雌性大鼠的LA阈值升高到相同水平（约22微摩尔/升的LA）。最后，我们评估了雄性大鼠以及用苯甲酸雌二醇或油剂处理的去卵巢（OVX）雌性大鼠对蔗糖中混合的11、22、44和88微摩尔/升LA的舔舐反应。在10秒的试验中，所有大鼠对LA浓度增加的舔舐反应都增加，但OVX大鼠对较低的LA浓度（22微摩尔/升）有反应，而雄性大鼠则对44微摩尔/升有反应。然而，雌二醇并未影响这一结果。总体而言，这些实验表明，雄性和雌性大鼠利用味觉来辨别LA，并且支配舌尖味蕾的鼓索神经在这种辨别中起作用。此外，脂肪偏好的性别差异可能取决于脂肪酸味觉阈值的差异以及与脂肪结合的味觉刺激。
