Meeting Abstract
Lumbricus 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-gizzards. Since acetylcholine (ACh) stimulates the contractility of crop-gizzards at room temperature, we also examined their responses to this molecule at various temperatures. We placed the organs 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 crop-gizzards in constant-temperature tissue baths and applied increasing acetylcholine concentrations. 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 from 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 rate and amplitude. 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 ACh efficacy and potency on contraction rate compared to 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.
