Abstract
Temperature perturbations affect neuronal activities by altering the intrinsic ionic conductances that underlie the electrical properties of neurons. High temperatures can lead to an excessive increase in conductance and a shunt of neuronal responses, which decreases cell excitability and eventually causes a loss of neuronal activity. Surprisingly, though, many neuronal circuits continue to function in spite of these challenges, suggesting that they possess compensatory mechanisms to overcome the detrimental effects of temperature. In the crustacean stomatogastric ganglion even small temperature increases lead to loss of neuronal activity. Previous studies have shown that the presence of a neuropeptide released from modulatory projection neurons rescues the neuronal activity by counterbalancing the excessive conductance increase caused by high temperatures. However, it is not clear whether this rescue mechanism is common to many neurons or an idiosyncrasy of the stomatogastric system. We address this question using primary cell cultures derived from neural tissue of the marbled crayfish, Procambarus virginalis. Cell cultures allow us to characterize the responses of crustacean neurons from many different origins independent from circuit influences, and to test their responses to temperature challenges. Because neuropeptides are ubiquitously present in the nervous system and marbled crayfish survive large temperature fluctuations with seemingly few effects on behavioral effects, we hypothesize that most, if not all crustacean neurons have the ability to overcome temperature perturbations and that peptide modulators enable them to do so. To test our hypothesis we are challenging cultured neurons with temperature changes and analyze (1) the collective neuronal responses by measuring field potentials and (2) individual and collective neuronal responses using calcium imaging. Neurons will be raised under constant temperature conditions for a prolonged time period to exclude homeostatic adaptations of their temperature responses. To analyze how far cultured neurons withstand temperature fluctuations, we will compare their activities before and during a transient increase in temperature. We will determine the role of peptide modulators in temperature compensation by subjecting neurons to different modulators and observing changes in their temperature responses. We predict that, like neurons in the stomatogastric ganglion, cultured neurons can withstand fluctuations in temperature better in presence of neuromodulators. This would indicate the essential role played by the peptide neuromodulators in restoring neuronal activity when faced with changes in temperature.
Keywords: None provided.
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