Delivering Traumatic Brain Injury to Larval Zebrafish

Abstract

We describe a straightforward, scalable method for administering traumatic brain injury (TBI) to zebrafish larvae. The pathological outcomes appear generalizable for all TBI types, but perhaps most closely model closed-skull, diffuse lesion (blast injury) neurotrauma. The injury is delivered by drop** a weight onto the plunger of a fluid-filled syringe containing zebrafish larvae. This model is easy to implement, cost-effective, and provides a high-throughput system that induces brain injury in many larvae at once. Unique to vertebrate TBI models, this method can be used to deliver TBI without anesthetic or other metabolic agents. The methods simulate the main aspects of traumatic brain injury in humans, providing a preclinical model to study the consequences of this prevalent injury type and a way to explore early interventions that may ameliorate subsequent neurodegeneration. We also describe a convenient method for executing pressure measurements to calibrate and validate this method. When used in concert with the genetic tools readily available in zebrafish, this model of traumatic brain injury offers opportunities to examine many mechanisms and outcomes induced by traumatic brain injury. For example, genetically encoded fluorescent reporters have been implemented with this system to measure protein misfolding and neural activity via optogenetics.

1 Appendix 1. Code with Explanatory Comments

// Zebrafish TBI pressure sensor measurement // Alexander H. Burton (2020) // define variable holding photoresistor reading float light = 0; // define variable holding pressure reading             float pressure = 0; // define light level to trigger pressure recording \r\n// reduce value of lightthreshold to decrease sensitivity of trigger // increase value of lightthreshold to increase trigger sensitivity float lightthreshold = 400;  // define logical variable that indicates recording should be started boolean start = false;       // board setup // opens serial monitor at the highest baud rate and starts a new line void setup() {  Serial.begin(2000000);      Serial.println("\n");      } // main program loop void loop() {    // read the photoresistor circuit    light = analogRead(A5);       // if the photoresistor voltage fell below threshold (i.e. the light beam    // was broken) set start to ‘true’ to initiate the pressure readings    if (light < lightthreshold) {      start = true;    }    // if light beam was broken, start taking pressure readings    if (start == true) {      // take 2000 consecutive readings     // this value can be changed to make the recording window longer or shorter     // e.g. for (int i = 0; i < 500; i++) takes 500 measurements      for (int i = 0; i < 2000; i++) {       // read the pressure sensor        pressure = analogRead(A1);        // write the timestamp and pressure reading to the serial monitor     Serial.print(millis());        Serial.print("\t");    Serial.print(pressure);     Serial.println(" ");      }      // stop recording until trigger is activated again      start = false;    } }