Caenorhabditis elegans is an informative model to study the neural basis of feeding. A useful paradigm is one in which adult nematodes feed on a bacterial lawn which has been pre-loaded with pharmacological agents and the effect on pharyngeal pumping rate scored. A crucial aspect of this assay is the availability of good quality bacteria to stimulate pumping to maximal levels. A potential confound is the possibility that the pharmacological agent impacts bacterial viability and indirectly influences feeding rate. Here, the actions of nicotine on pharyngeal pumping of C. elegans and on the Escherichia coli bacterial food source were investigated. Nicotine caused an immediate and concentration-dependent inhibition of C. elegans pharyngeal pumping, IC₅₀ 4 mM (95% CI = 3.4 mM to 4.8 mM). At concentrations between 5 and 25 mM, nicotine also affected the growth and viability of E. coli lawns. To test whether this food depletion by nicotine caused the reduced pumping, we modified the experimental paradigm. We investigated pharyngeal pumping stimulated by 10 mM 5-HT, a food ‘mimic’, before testing if nicotine still inhibited this behaviour. The IC₅₀ for nicotine in these assays was 2.9 mM (95% CI = 3.1 mM to 5.1 mM) indicating the depletion of food lawn does not underpin the potency of nicotine at inhibiting feeding. These studies show that the inhibitory effect of nicotine on C. elegans pharyngeal pumping is mediated by a direct effect rather than by its poorly reported bactericidal actions.

秀丽隐杆线虫是研究进食神经基础的信息丰富的模型。一种有用的范例是，成虫线虫以预先装载有药物的细菌菌苔为食，并对咽部泵送速率的影响进行评分。该测定的一个重要方面是优质细菌的可用性，以刺激泵送至最大水平。一个潜在的混淆是药物可能影响细菌活力并间接影响摄食率。在这里，研究了尼古丁对秀丽隐杆线虫咽部泵送和大肠杆菌食物来源的作用。尼古丁对线虫咽部泵送产生立即且浓度依赖性的抑制，IC ₅₀ 4 mM（95% CI = 3.4 mM 至 4.8 mM）。浓度在 5 至 25 mM 之间时，尼古丁还会影响大肠杆菌菌苔的生长和活力。为了测试尼古丁造成的食物消耗是否会导致泵送减少，我们修改了实验范例。我们研究了 10 mM 5-HT（一种食物“模拟物”）刺激的咽部抽吸，然后测试尼古丁是否仍然抑制这种行为。这些测定中尼古丁的IC ₅₀为 2.9 mM（95% CI = 3.1 mM 至 5.1 mM），表明食物草坪的消耗并不支持尼古丁抑制进食的效力。这些研究表明，尼古丁对线虫咽部泵送的抑制作用是通过直接作用介导的，而不是通过其报道很少的杀菌作用介导的。