Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, AB T2N 4N1, Canada.
J Exp Biol. 2011 Aug 1;214(Pt 15):2528-33. doi: 10.1242/jeb.058024.
The great pond snail, Lymnaea stagnalis, is commonly used as a model species to study how stress affects the ability to form long-term memory (LTM); however, we still have little information about how the snail senses stressful stimuli. The osphradium is an external sensory organ that demonstrates electrophysiological responses to a variety of external chemical stimuli. We examined the role, if any, played by the osphradium in sensing two environmental stressors, crowding and low environmental calcium, both known to block LTM in intact animals. We severed the osphradial nerve, blocking external sensory input from this organ to the central nervous system, and then exposed the snails to low environmental calcium or crowding stress to assess whether these stressors continued to block LTM formation. When exposed to low environmental calcium, snails with their osphradial nerve severed responded as if they were maintained in our standard calcium environment. That is, they did not respond to low calcium as a stressor blocking LTM; therefore, the osphradium plays a crucial role in mediating how snails respond to this stressor. However, following crowding, LTM formation was blocked in both control groups and snails that had the osphradial nerve severed, indicating that sensory information from the osphradium is not required to sense crowded conditions. Together these data show that two stressors that result in the same behavioural phenotype, blocking LTM formation, do so via two distinct sensory pathways.
大型圆田螺（Lymnaea stagnalis）通常被用作研究应激如何影响形成长期记忆（LTM）能力的模式生物；然而，我们对于蜗牛如何感知应激刺激仍然知之甚少。触角器是一种外部感觉器官，对各种外部化学刺激表现出电生理反应。我们研究了触角器在感知两种环境应激源（拥挤和低环境钙）中的作用，如果有的话，这两种应激源已知会阻止完整动物形成 LTM。我们切断了触角神经，阻止了来自该器官的外部感觉输入到中枢神经系统，然后使蜗牛暴露于低环境钙或拥挤应激下，以评估这些应激源是否继续阻止 LTM 形成。当暴露于低环境钙时，切断触角神经的蜗牛的反应就好像它们被维持在我们的标准钙环境中一样。也就是说，它们不会将低钙作为阻止 LTM 的应激源；因此，触角器在介导蜗牛对这种应激源的反应中起着至关重要的作用。然而，在拥挤之后，对照组和切断触角神经的蜗牛的 LTM 形成都被阻断，这表明来自触角器的感觉信息不是感知拥挤条件所必需的。这些数据表明，两种导致相同行为表型（阻止 LTM 形成）的应激源通过两条不同的感觉途径起作用。
