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Research Team
Research Team
Caleigh Naylon
Caleigh Naylon
Neuroscience Comajor, Microbiology Major
Dawn Blitz
Dawn Blitz
Biology Department
Introduction
Introduction
Central pattern generators (CPGs) are the neural circuits responsible for rhythmic behaviors. Some activities may be spontaneously and perpetually active (e.g., breathing), while others are state dependent and must be initiated by extrinsic modulatory input (e.g., walking).
In the crab, the Stomatogastric Ganglion (STG) contains circuitry that underlies the continuous filtering rhythm (pyloric) and the state dependent chewing rhythm (gastric mill). This system is well defined and flexible.
GPR1 and GPR2 are two bilateral pairs of sensory receptor cells in the crab stomatogastric nervous system. They are both proprioceptors, meaning they respond to changes in muscle stretch, but they innervate different muscles in the stomach of the crab (GPR1: gm8b, GPR2: gm9a and cpv3a) (1, 2). They can be stimulated via the mgn and gpn (GPR1 and GPR2, respectively).
GPR neurons send axonal projections to the STG and the anterior ganglia as well (CoGs). Here, they excite MCN1 and CPN2, two modulatory projection neurons necessary and sufficient for gastric mill rhythm production (3, 4).
Furthermore, it has been observed that pyloric activity slows upon GPR stimulation, then increases in frequency and regularizes (5). It has not been determined if there is a difference between these these distinct receptor neurons on this rhythmic activity.
Research Questions
Research Questions
Through electrical stimulation of gpn and mgn, we ask the following questions:
Is the firing frequency of projection neurons differentially affected?
2. Is the pyloric rhythm differentially affected?
Methods
Methods
Cancer borealis and Metacarcinus magister in vitro stomatogastric nervous system preparations were pinned on a silicone elastomer-lined petri dish. Nerves were recorded from extracellularly using a Vaseline well and electrode technique.
Sharp electrode current clamp was performed on GM neuron in the STG. GM was then hyperpolarized and the recording filtered so that the EPSPs due to CPN2 spikes could be quantified. The instantaneous frequency was calculated as 1/distance between CPN2 spikes (interspike interval) in seconds. Frequency of MCN1 was calculated similarly via spikes in the extracellular recording of the ion. Frequency of PD was calculated using using the interburst interval of this neuron in extracellular recording of the pdn.
Analysis was performed on 30 second pre stimulation, 6 second stimulation (if able), and 30 second post stimulation data. All statistical analysis was performed in SigmaPlot software.
Results
Results
See figures below.
CPN2 Firing Frequency
CPN2 Firing Frequency
Instantaneous frequency over time for stimulation of mgn and gpn at 5 Hz and 30 Hz stimulation frequencies.
MCN1 Firing Frequency
MCN1 Firing Frequency
Instantaneous frequency over time for stimulation of mgn and gpn at 5 Hz and 30 Hz stimulation frequencies.
Artifacts prevented analysis during stimulation.
Pyloric Frequency
Pyloric Frequency
Average pyloric frequency (PD bursts) during 30 seconds pre stimulation, 6 seconds during (if able), and 30 seconds post stimulation. Statistical tests did not find statistical differences, but it is very low power. Qualitative observations of activity differences warrant further research.
Conclusions and Future Study
Conclusions and Future Study
Conclusions:
CPN2 activity decreases in frequency during GPR stimulation, then increases post stimulation
Compared to mgn stimulation, there appears to be a larger increase in both CPN2 and MCN1 activity following stimulation of gpn
No significant differences in pyloric rhythm frequency, but further methods to quantify observed potential differences required
Future Directions:
Determine if there is a difference in duration of effect on projection neuron and pyloric activity between gpn and mgn
Further examine frequency dependence of GPR stimulation on all parameters
Induce a gastric mill rhythm to determine the effects on this rhythm as well
The following is an image of poster presented at the 2026 Undergraduate Research Forum
Acknowledgements
Acknowledgements
Thank you to Hope Bishop for assistance with electrophysiology experiments and Ryan Zielinski for your assistance with data analysis.
References
References
1. P. S. Katz, M. H. Eigg, & R. M. Harriss-Warrick. (1989). J. Neurophysiol
2. P. S. Katz & R. M. Harris-Warrick. (1989). J. Neurophysiol
3. D. M. Blitz, M. P. Beenhakker, & M. P. Nusbaum (2004). J. Neurosci.
4. M. P. Beenhakker, & M. P. Nusbaum (2004). J. Neurosci.
5. P. S. Katz & R. M. Harris-Warrick. (1990). J. Neurosci
NACE Career Readiness Competencies
NACE Career Readiness Competencies
Career and Self Development - Through this experience, I have identified avenues for further exploration that I am curious about. I have embraced opportunities to pursue learning opportunities and grow as a scientist.
Communication - I have learned to organize complex data in order to articulate ideas and findings in a clear and organized manner. I have also learned to identify when I need guidance and feedback from my mentor and lab mates.
Critical Thinking - This project has allowed me to think critically about focused and detail-oriented concepts as well as develop my skills to detect nuances. It has also allowed me to develop rationale and implications for my research.
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