UC San Diego

The brain contains a diverse array of neurons that vary in complexity. Investigating the properties and connectivity of these neurons is essential to identifying the relationships between brain function, behavior, and disease. A useful animal model for studying the brain is the albino Xenopus laevis tadpole due to its transparent skin and visible external development. One region of interest is the optic tectum, a midbrain region homologous to the mammalian superior colliculus, that is responsible for visual processing and visuomotor behaviors. While the optic tectum is known to be responsible for mediating visually-guided behaviors, knowledge is limited on what neuronal cell types exist in the optic tectum and how these neurons interact to cause behavior. In order to characterize excitatory and inhibitory neuronal cell types in the optic tectum, we used live imaging of single cells expressing GFP in Stage 47 albino Xenopus laevis and reconstructed the neurons’ dendritic and axonal morphology. Post hoc GABA immunolabeling of cross sections was used to characterize the cell as inhibitory or excitatory. Here we present the comparison of excitatory and inhibitory neurons in the optic tectum based on their dendritic and axonal characteristics. Specifically, we compared their total axon and dendrite length, axon and dendrite branch tip number, number of primary dendrites, deepest dendrite depth, and axon projections, to investigate whether any of these parameters may differentiate between excitatory and inhibitory neuronal cell types. We also experimented to optimize the published SWITCH protocol for our methods to improve our post hoc GABA immunostaining.