Morphine alleviates pain after heart cryonjury in zebrafish without impeding regeneration

Nociceptive response belongs to a basic animal behavior facilitating adaptability and survival upon external or internal stimuli. Fish, similarly to higher vertebrates, also possess nociceptive machinery. Current protocols involving procedures performed on adult zebrafish including heart cryoinjury do not, however, take into account the adverse effects including pain that may potentially arise from these methodologies. Here, we assess the effect of two analgesics, lidocaine and morphine, followed after the heart cryoinjury in zebrafish. Monitoring swimming behaviour together with histology and gene expression analysis at the single cell level using scRNA sequencing and RNAscope fluorescent in situ hybridization technology, we show morphine, but not lidocaine, significantly improves animal welfare 6 hours post-cryoinjury, without impairing heart regeneration process. Altogether, morphine should be considered as the analgesic of choice to reduce post-surgical pain in adult zebrafish. Single cell RNAseq of morphine treated and untreated zebrafish heart samples at 3, 7 and 15 days post injury

伤害感受反应（nociceptive response）是一类基础动物行为，可帮助机体在遭遇外源性或内源性刺激时提升适应性与生存能力。鱼类与高等脊椎动物类似，同样拥有伤害感受系统（nociceptive machinery）。然而，当前针对成年斑马鱼的实验操作方案（包括心脏冷冻损伤模型），并未考虑此类操作可能引发的包括疼痛在内的各类不良反应。本研究以斑马鱼心脏冷冻损伤模型为对象，评估了利多卡因（lidocaine）与吗啡（morphine）两种镇痛剂在损伤后给药的干预效果。本研究通过游泳行为学监测、组织学分析，以及采用单细胞RNA测序（single cell RNA sequencing, scRNA-seq）和RNAscope荧光原位杂交技术（RNAscope fluorescent in situ hybridization）开展的单细胞水平基因表达分析，结果显示：在冷冻损伤后6小时，吗啡可显著改善动物福利，而利多卡因无此作用，且不会抑制心脏再生进程。综上，吗啡可作为成年斑马鱼术后镇痛的首选镇痛剂。本数据集包含损伤后3天、7天及15天的吗啡处理组与未处理组斑马鱼心脏样本的单细胞RNA测序数据。