In Vivo Study Of Dynamics And Stability Of Dendritic Spines On Olfactory Bulb Interneurons In Xenopus Laevis Tadpoles

This thesis contains two parts. A new model was established in Xenopus tadpoles to explore dendritic spine dynamics in vivo, and the quantitative measurements of the adult zebrafish Optokinetic response (OKR) and the Optomotor response (OMR)were successfully successfully set up to study visual behavior.In the first part:Dendritic spines undergo continuous remodeling during development of the nervous system. Their stability is essential for maintaining a functional neuronal circuit. Spine dynamics and stability of cortical excitatory pyramidal neurons have been explored extensively in mammalian animal models. However, little is known about spiny interneurons in non-mammalian vertebrate models.In the present study, neuronal morphology was visualized by single-cell electroporation. Spiny neurons were surveyed in the Xenopus tadpole brain and observed to be widely distributed in the olfactory bulb and telencephalon. DsRed-or PSD95-GFP-expressing spiny interneurons in the olfactory bulb were selected for in vivo time-lapse imaging.Dendritic protrusions were classified as filopodia, thin, stubby, or mushroom spines based on morphology. Dendritic spines on the interneurons were highly dynamic, especially the filopodia and thin spines. The stubby and mushroom spines were relatively more stable, although their stability significantly decreased with longer observation intervals. The 4 spine types exhibited diverse preferences during morphological transitions from one spine type to others. Sensory deprivation induced by severing the olfactory nerve to block the input of mitral/tufted cells had no significant effects on interneuron spine stability. Hence, a new model was established in Xenopus laevis tadpoles to explore dendritic spine dynamics in vivo.In the second part:OKR and the OMR are useful means for visual function testing and visual related mutants screening. Because of their simplicity, stereotype and effectiveness, they have been widely used in the study of zebrafish larvae. However, analysis methods of OKR and OMR in adult zebrafish are rarely reported. In this study, methods of inducing zebrafish OMR and OKR behavior, approaches of tracking the eye movement using Pattern Match algorithm, as well as tracking swimming adult zebrafish using background subtraction, are presented. The quantitative measurements of the adult zebrafish OKR and OMR behavior were successfully set up. Based on such methods, the binocular vision of adult zebrafish area was found to make a certain contribution to OKR behavior. Moreover,themonocular vision of adultzebrafishshowed a certain degree of directional sensitivity to moving gratings. OMR behavior can also be used to evaluate the recovering visual function of adult zebrafish after the optic nerves were crushed, Such approaches can also be applied to the zebrafish larvae OKR. The abnormity of OKR behaviour phenomenon of period1b mutant larvae fish was detected in the initial observation.