Field Kristin L, Beauchamp Gary K, Kimball Bruce A, Mennella Julie A, Bachmanov Alexander A
Monell Chemical Senses Center, 3500 Market St., Philadelphia, PA 19104, USA.
J Comp Psychol. 2010 Nov;124(4):455-9. doi: 10.1037/a0020792.
Rejection of bitter substances is common in many species and may function to protect an animal from ingestion of bitter-tasting toxins. Since many plants are bitter, it has been proposed that high tolerance for bitterness would be adaptive for herbivores. Earlier studies conducted on herbivorous guinea pigs (Cavia porcellus) have been used to support this proposal. We tested guinea pigs with bitter plant secondary metabolites (salicin, caffeine, quinine hydrochloride) and bitter protein hydrolysates (two types of hydrolyzed casein, hydrolyzed soy) in a series of two-choice preference tests. For comparison, we tested two nonherbivorous mouse species (Mus musculus and Peromyscus leucopus). Guinea pigs did show weaker avoidance of quinine hydrochloride than did the mice, confirming predictions generated from earlier work. However, guinea pigs had similar responses to caffeine as did Peromyscus. Both of these species showed weaker avoidance responses than Mus to 10 mM caffeine. For salicin, guinea pigs were the only species to avoid it at 10 mM and their preference scores at this concentration were significantly lower than for the two mice species. Guinea pigs avoided all of the protein hydrolysates more strongly than the other species. Responses to the protein hydrolysates did not reflect the patterns observed with the simple bitter compounds, suggesting that other properties of these complex stimuli may be responsible for guinea pig avoidance of them. Our results suggest caution in accepting, without further empirical support, the premise that guinea pigs (and herbivores in general) have a generalized reduced bitter sensitivity.
许多物种都存在对苦味物质的排斥反应，这可能起到保护动物避免摄入苦味毒素的作用。由于许多植物都带有苦味，因此有人提出，对苦味的高耐受性对食草动物具有适应性。早期对草食性豚鼠（豚鼠）进行的研究已被用于支持这一观点。我们在一系列二选一偏好测试中，用苦味植物次生代谢物（水杨苷、咖啡因、盐酸奎宁）和苦味蛋白水解物（两种水解酪蛋白、水解大豆）对豚鼠进行了测试。为作比较，我们测试了两种非食草性小鼠物种（小家鼠和白足鼠）。豚鼠对盐酸奎宁的回避反应确实比小鼠弱，这证实了早期研究得出的预测。然而，豚鼠对咖啡因的反应与白足鼠相似。这两个物种对10 mM咖啡因的回避反应都比小家鼠弱。对于水杨苷，豚鼠是唯一在10 mM时就回避它的物种，而且它们在该浓度下的偏好分数显著低于两种小鼠物种。豚鼠对所有蛋白水解物的回避反应都比其他物种更强。对蛋白水解物的反应并未反映出对简单苦味化合物所观察到的模式，这表明这些复杂刺激的其他特性可能是豚鼠回避它们的原因。我们的研究结果表明，在没有进一步实证支持的情况下，谨慎接受豚鼠（以及一般食草动物）普遍降低苦味敏感度这一前提。
