Serotonergic modulation of Mauthner neurons in larval zebrafish

In recent decades, zebrafish have become a popular organism in neuroscience research. This is primarily because of the homogenous nature of what are known as reticulospinal neurons. These neurons, located in the hindbrain, control locomotive (e.g., swimming) and escape behaviors via descending axonal connections to lateral musculature. Dominating the reticulospinal neuron group are the Mauthner neurons. This pair of morphologically distinctive neurons is referred to as "command neurons" in the reticulospinal group. Recent studies involving antibody labeling reveal a distinctive clustering of serotonin (5-HT) associated proteins in the Mauthner dendritic regions. This would imply that 5-HT plays a direct role in the modulation of Mauthner neuron activity. In this study, we attempt to experimentally demonstrate a functional relationship between 5-HT and the Mauthner neuron through the administration of the SSRI fluoxetine and Ca²+ imaging techniques. Results indicate no significant change Ca²+ and latency of response. Interestingly, these data indicate a difference in responsiveness (i.e., firing or no firing) with the fluoxetine group showing an 8% increase. These data shed light upon the Mauthner neuron and 5-HT, as well as the possible considerations of future research