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Graduation Term
Spring 2026
Degree Name
Master of Science (MS)
Department
School of Biological Sciences
Committee Chair
Wolfgang Stein
Committee Member
Andres Vidal-Gadea
Committee Member
Paul Garris
Abstract
Climate change is driving increases in ocean temperatures, posing challenges for the nervous systems of marine ectotherms. This thesis tests whether neuromodulatory input enables pattern-generating circuits in the stomatogastric nervous system (STNS) to maintain motor output at higher temperatures. Using Callinectes sapidus and Cancer borealis, I tested whether descending neuromodulatory projection neurons support rhythmic motor output at elevated temperatures.
Extracellular recordings in C. sapidus demonstrated that the pyloric rhythm remained functional across a wider temperature range when both the stomatogastric ganglion (STG) and the upstream commissural ganglia (CoGs) were heated together, compared to heating the STG alone.
All remaining experiments were performed in C. borealis. Recordings from identified modulatory projection neurons did not show a consistent temperature-dependent change in firing rate. Mass spectrometry did not detect CabTRP Ia in collected saline, possibly due to low extracellular concentrations, either because peptide release did not increase across temperatures or because the samples were diluted during collection. Voltage clamp recordings of the lateral gastric (LG) neuron were used to measure the modulator-induced inward current (IMI). When the pathway containing the Modulatory Commissural Neuron 1 (MCN1) was stimulated, IMI amplitudes were significantly larger at higher temperatures. In contrast, when CabTRP Ia was bath applied to isolate the postsynaptic component of IMI, current amplitudes did not differ across temperatures. The presence of a temperature effect when both presynaptic release and postsynaptic receptor activation were engaged, and its absence when only the postsynaptic response was examined, suggests that the temperature dependence of IMI arises from a presynaptic contribution.
Together, these results provide partial support for the hypothesis that neuromodulatory input contributes to the temperature robustness of motor patterns in the STNS. However, the findings are mixed and do not allow a definitive conclusion regarding the extent to which temperature-dependent changes in neuromodulatory signaling sustain rhythmic activity at elevated temperatures. Further work will be required to measure peptide release under warming directly and to determine how presynaptic and network-level mechanisms interact to support motor pattern stability as temperatures rise.
Access Type
Thesis-ISU Access Only
Recommended Citation
Sanford, Mason D., "Does Increased Synaptic Release From Modulatory Projection Neurons Enable Continued Neuronal Pattern Generation at Increasing Temperature?" (2026). Theses and Dissertations. 2339.
https://ir.library.illinoisstate.edu/etd/2339