Correlated changes in behaviour and glutamate receptor expression as a result of early stimulation in Caenorhabditis elegans

The effects of early sensory experience on the development of central nervous system structures and behavior are the focus of much ongoing research. Previous studies have demonstrated that exposing animals to sensory enriched environments produced significant changes in the nervous system and accelerated and improved the development of complex cognitive behaviors such as learning and memory; however the long-term effects of sensory enriched environments on the nervous system and behavior remain unknown. In this study, I investigated the long-term effects that an enhancement in mechanosensory experience produced on adult behavior and glutamate receptor-1 (GLR-1) distribution in the nematode Caenorhabditis elegans (C elegans). I found that C. elegans exposed to an enhancement in mechanosensory stimulation exhibited different behavioral and molecular outcomes depending on the temporal pattern of mechanosensory stimulation, the age of the worm stimulated and the age of the worm tested. Early spaced mechanosensory stimulation at a long inter-stimulus interval produced two independent behavioral effects, an early enhancement at 3 days followed by a depression at 5 days. Both behaviors were dependent on glutamate activity and were associated with a positively correlating change in both glutamate receptor-1 protein distribution and mRNA levels. The 3 day behavioral enhancement was not observed when spaced mechanosensory stimulation was delivered later in larval development, suggesting a critical period for these effects early in larval development. There appeared to be no critical period for the depressed behavioral response observed at 5 days; however only the depressed behavioral response of 5 day old worms was found to be sensitive to reconsolidation blockade. These results suggest that early mechanosensory stimulation produces two independent effects in adult worms: an early developmental effect in 3 day old worms which is mediated by one cellular event and a long-term memory effect at 5 days which is mediated by a separate cellular phenomenon. The results from this study have provided novel information into the long-term effects that an enhancement in early sensory experience had on the behavior and molecular properties of the adult nervous system, and provided the foundation for future research in this field.Medicine, Faculty ofGraduat