Prolonged Micromolar Ketamine Exposure Induces Dorsal Spinal Neuron Apoptosis and Locomotor Deficits During Early Development: Insights From FRET‐Based Sensor Zebrafish

ABSTRACT Multiple studies have reported the neurodevelopmental toxicity of the general anesthetic ketamine. However, whether ketamine can induce apoptosis in developing neurons remains poorly understood, largely because of the lack of effective in vivo tools to sensitively detect transient neuronal apoptosis. In the present study, we developed sensor zebrafish that allow in vivo apoptosis sensing and high‐throughput behavioral tracking to study the neurodevelopmental toxicity of ketamine. By stably expressing a genetically encoded fluorescence resonance energy transfer (FRET)‐based biosensor in the nervous system, we achieved highly sensitive detection of neuronal apoptosis in live zebrafish. The sensor zebrafish enabled spatiotemporal detection of transient neuronal apoptosis, which is often missed by traditional methods. Using the sensor zebrafish, we found that long‐term (48 and 72 h) exposure to micromolar (50 and 100 μM) ketamine induced discrete yet consistent apoptosis of developing neurons at the dorsal edge of the spinal cord, where primary sensory neurons and interneurons are localized. To evaluate functional deficits following the loss of these neurons, we performed high‐throughput swimming tracking analysis. The sensor zebrafish showed reductions in maximum acceleration and velocity after ketamine exposure. This sensor zebrafish platform provides new insights into the neurotoxicity of ketamine in the developing nervous system.