Temperature on earth and thus body temperature in animal can vary widely. Ectotherms are animals with the body temperature that primarily depends on external hit source. Because of that dependence, they are directly affected by changes in temperature, which can also modify their metabolic rates. Lumbricus terrestris (L. terrestris) is an anecic earthworm that experiences different thermal environments. Most experiments examining the effects of neurotransmitters on their smooth muscles have been performed at room temperature. Since these animals are found at cooler temperatures, we decided to examine how temperature affects the contractility of their isolated crop-gizzard. Since acetylcholine (ACh) stimulates the contractility of crop-gizzards at room temperature, we also investigated their response to this chemical at various temperatures. We placed the organ in temperature-regulated tissue baths and recorded spontaneous contractions. Temperature was varied from 20oC to 15oC and 10oC, then back up to 15oC and 20oC. We recorded any changes at each temperature. We then placed the crop-gizzards in constant-temperature tissue baths and applied increasing concentrations of acetylcholine. The resulting data were used to create ACh log-concentration response curves. Results from the first experiments showed the baseline contraction amplitudes dropped when moving from 20oC to 15oC and 10oC, and rose when the temperature increased 10oC to 15oC and 20oC. The contraction rates dropped at 10oC and then rose at 15oC and 20oC. ACh caused an increase in both contraction rates and amplitudes. Temperatures of 10oC and 20oC caused a decrease in ACh efficacy and potency on the contraction amplitude compared to 15oC and room temperature, while 10oC and room temperature caused a decrease in efficacy and potency on contraction rate compared 15oC and 20oC. Our results suggest that the earthworm smooth muscle spontaneous contractility and responses to ACh decreased at 10oC, while at warmer temperatures the responses were more variable. Moreover, the statistical analysis performed by Dr. Schulz concluded that there was a strong effect of ACh concentrations on the smooth muscle contractions, but there was very little to no effect of temperature.
|Commitee:||Williams, Jason, Schulz, Kurt, Lee, Danielle|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 82/3(E), Masters Abstracts International|
|Keywords:||Acetylcholine, Crop-gizzard, Lumbricus terrestris, Smooth muscle, Temperature|
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