Tactile versus Electrical Sensory Input to Stimulate the Zebrafish (Danio rerio) Escape Response

The escape response, or c-start response, provides a quantifiable assay for measuring changes in the communication of the neural circuit components that govern survival behaviors. Initiation of the escape response relies on the detection of mechanostimuli that trigger Mauthner neurons or M-cells, a pair of commissural neurons that extend the full length of the spinal cord to integrate stimuli through interneurons. Mauthner cells integrate directional information from stimuli, and convey bilateral, excitatory responses to motor neurons innervating trunk muscles. Communication between Mauthner neurons by commissural interneurons induces reciprocal inhibition necessary for coordinated movement. From an early embryonic period (16 hpf), zebrafish receive and respond to direct touch stimuli with escape behaviors. Previous studies comparing head touch-induced responses with responses elicited by an auditory cue indicate that fish do not develop auditory/ vestibular induced responses until 70 hours post fertilization. From this developmental milestone, instead of needing direct touch stimuli, the fish employs the octavolateralis system to detect disturbances in the water. The escape response has been extensively characterized in larval zebrafish and is often used for testing innate and genetically altered reactions to stimuli. As a prelude to my thesis research regarding treatment of spasticity through reestablishment of balanced excitatory and inhibitory inter-neuronal signaling in the escape circuit, we investigate the relationship between c-start responses evoked through electrical and tactile stimuli. The importance of standard repeatable methods to elicit escape behaviors removes variables that may influence the integrity of the measured escape response and our ability to elicit consistent behaviors