Discovery of Novel Anesthetic Compounds Using Zebrafish Larvae
INTRODUCTION: Novel general anesthetic compounds for use in medicine can provide increased treatment options for patients undergoing invasive medical procedures such as surgery. Zebrafish larvae have recently emerged as a platform for high throughput screening of neuroactive compounds. In our lab, we are using zebrafish larvae to conduct a high throughput screen of over 2,000 uncharacterized drug compounds for possible anesthetic properties. Furthermore, we are testing new combinations of etomidate and MPAB, two known anesthetics acting on the GABA-A receptor, to determine agonistic or antagonistic interactions; we aim to reduce toxic side effects of various drug combinations and to exploit the beneficial properties of these drugs to improve treatment efficaciousness. METHODS: After a 0.2 second bright white light stimulus in dark-adapted 7 day old post-fertilization Tu zebrafish larvae, the Photomotor response (PMR) was analyzed using a specialized motion tracking video system (ViewPoint Zebralab). This bright stimulus startles the zebrafish into a brief burst of movement. Anesthetic effects of new compounds were qualified by calculating the PMR inhibition, representing the decrease in movement after the stimulus and sedative effects were quantified by recording pre-stimulus basal activity inhibition, representing the normal zebrafish movement during periods of no stimulus. RESULTS: Several prospective novel anesthetic compounds have been identified and our lab is currently performing more screens to assess the reversibility and potency of each drug. Specifically, we discovered Compound 84 which shows a significantly higher potency (IC50 = 8.99 μM , 95% IC: 6.38 to 12.7 μM) and normal reversibility (representing the zebrafish ability to recover from drug PMR inhibition overnight). CONCLUSION: Zebrafish photomotor response is a promising method for high throughput identification of novel anesthetics. Additionally, co-administration of MPAB with etomidate can potentially reduce dosage requirements in anesthetics, therefore, providing beneficial drug combination options to reduce side effects in higher risk patients.