Serotonin (5-HT) takes a key position in regulating vital functions, such as cardio-ventilatory activity, locomotion and behaviour. Selective serotonin reuptake inhibitors (SSRIs) modulate the serotonergic system and thus affect these functions. Rhythmic behaviours, such as cardio-ventilatory activity, are controlled by central pattern generators, which in turn are regulated by 5-HT. In crustaceans, 5-HT also regulates the synthesis and secretion of crustacean hyperglycaemic hormone, a pleiotropic hormone involved in the mobilisation and release of glucose into the haemolymph, thus stimulating the animal’s activity. As a matter of consequence, SSRIs may affect cardio-ventilatory activity. In order to examine how the SSRIs affect fundamental physiological parameters based on rhythmic behaviours in decapods, cardio-respiratory activity in the shore crab Carcinus maenas was assessed after pericardial injection of a single dose of either 0.5 μM, 0.75 μM or 1 μM fluoxetine, respectively. Simultaneous recordings of heart and scaphognathite movements in both brachial chambers were conducted by measuring impedance changes in the respective body compartments. Injection of 5-HT had an immediate effect on cardio-ventilatory activities and strongly upregulated both cardiac and ventilatory activities. Fluoxetine showed similar effects, entailing moderate tachycardia and increased ventilation rates. Compared to 5-HT, these effects were delayed in time and much less pronounced. Metabolism of fluoxetine into the active compound nor-fluoxetine might account for the delayed action, whereas compensatory regulation of cardio-ventilatory frequencies and amplitudes are likely to explain the attenuation of the responses compared to the strong and immediate increase by 5-HT. Overall, the results suggest increased 5-HT levels in invertebrates following fluoxetine exposure, which are able to disturb physiological functions regulated by 5-HT, such as cardiac and respiratory activity.

5-羟色胺（5-HT）在调节重要功能（例如心脏换气活动，运动和行为）中处于关键位置。选择性5-羟色胺再摄取抑制剂（SSRIs）调节5-羟色胺能系统，从而影响这些功能。有节奏的行为，例如心脏换气活动，由中央模式发生器控制，而中央模式发生器又由5-HT调节。在甲壳类动物中，5-HT还调节甲壳类高血糖激素的合成和分泌，这是一种多效性激素，参与了葡萄糖的动员和向血淋巴的释放，从而刺激了动物的活动。因此，SSRI可能会影响心脏的通气活动。为了检查SSRI如何根据十足动物的节律行为影响基本的生理参数，梅氏肉心包注射后分别评估0.5μM，0.75μM或1μM氟西汀的剂量。通过测量各个身体腔室中的阻抗变化，同时记录两个肱室内的心脏和肩突运动。注射5-HT对心室通气活动有直接作用，并且强烈上调了心脏和通气活动。氟西汀显示相似的作用，导致中度心动过速和通气率增加。与5-HT相比，这些影响在时间上有所延迟，而且效果不明显。氟西汀代谢成活性化合物去氟西汀的作用可能是延迟作用的原因，而心脏通气频率和幅度的补偿性调节则可能解释了与5-HT的强而有力的增加相比，反应的减弱。总体而言，结果表明氟西汀暴露后无脊椎动物中5-HT水平升高，这能够干扰5-HT调节的生理功能，例如心脏和呼吸活动。