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Graduate
Category: Physical and Life Sciences
Degree Level: Ph.D.
Abstract ID#: 271
The role of ionic currents in distinguishing the pyloric and gastric dynamics in the stomatogastric ganglion in the American lobster Lin Zhu1, Joseph Ayers1,2
1,Department of Biology, Northeastern University 2, Department of Marine and Environmental Sciences, Northeastern University
Results
*$
1$
0.8$
30mM CsCl
0.6$
0.4$
0.2$
Riluzole'disrupts'gastric'
rhythms'at'50μM'
A
Control
B
Extracellular
recordings
Cycle'Frequency'(Percentage)'
*$
*$
Cycle'Frequency'(Hz)'
pdn
(V)
0.12$
−0.6
0
0.08$
2
3
Time (s)
4
5
0.2$
0$
Pyloric'rhythm' Gastric'rhythm'
Control$
Control
Riluzole$0.2mM$
Recover$
0.2$
1$
0.8$
0.6$
0.4$
0.2$
FFA$50$μM$
0$
Gastric'
Rhythm'
PD'
Unblock$
Control$
LP,PY'and' Gastric'
VD'
neurons'
FFA$0.1mM$
Unblock$
References
1
gpn(V)
0.04$
3
40µm 4AP
mvn(V)
4
vlvn(V)
5
gpn(V)
0.02$
4AP' Unblock'
40μM'
2
pdn(V)
pyn(V)
0.06$
Control'
1
0.4$
50 µm FFA
0.4$
1.2$
1. Ih is necessary for maintaining both the pyloric and gastric rhythms. Blocking Ih with
25-30mM CsCl 1) Increased pyloric cycle frequency 2) Reduced the burst duration of LP
neurons 3) Increased the burst duration of PY and VD neurons 4) Fully blocked gastric
activities. Unblocking Ih enhances the gastric rhythms.
2. INaP is necessary for maintaining both the pyloric and gastric rhythms. Blocking INaP
with 50µM Riluzole 1) Blocked the activities of LP neurons 2) Fully blocked the gastric
activities 3) Didn’t change the pyloric cycle frequency.
3. IA is necessary in maintaining the cycle frequencies of LP and PY neurons. Blocking IA
with 40µM 1) Reduced the cycle frequencies of LP and PY neurons to half of the cycle
frequency of PD neurons 2) Enhanced the gastric rhythms and increased the gastric
cycle frequency
4. ICAN is necessary in maintaining both pyloric and gastric rhythms. Blocking ICAN with
50µM FFA 1) Fully blocked the gastric activities 2) Didn’t affect the pyloric rhythms.
vlvn(V)
dlvn(V)
0.1$
0$
−0.5
0.6$
pyn(V)
gastric'rhythm'
0.2
−0.4
1$
0.8$
0.6$
1.4$
Conclusion
dlvn(V)
0.6$
0.14$
PD
(V)
Perfuse fresh
saline
to maintain
temperature
1.2$
FFA'blocks'both'pyloric'and'
gastric'rhythms'at'0.1mM'
mvn(V)
C
−0.4
1.4$
C
1.8$
0.8$
Control$
2$
Cycle'Frequency'(Hz)'
0.8$
Control
1.6$
Pyloric'
Rhythm'
Riluzole'blocks'both'pyloric'
and'gastric'rhythms'at'0.2'mM'
1.6$
FFA'blocks'gastric'rhythm' B
at'50μM'
0$
1.8$
0.4
0
C
PUT$SPIKE$TRAIN$
0.4$
• Interneuron$1$(Int$1)$$
• Lateral&gastric&(LG)&
0.2$
• Gastric&(GM)&
• Medial&gastric&(MG)&
0$
• Dorsal$gastric$(DG)$$
PD'
VD'
LP'
PY'
• Lateral$posterior$gastric$
(LPG)$
Control$
4AP$40μM$
Unblock$
• Anterior$median$(AM)$ 4AP'enhances'the'
−0.2
0.2$
CsCl'
Unblock'
100mM'
Pyloric$rhythm$
Gastric$rhythm$
1$
Extracellular and Intracellular Recordings
Intracellular
recordings
0.4$
Control'
1.2$
Gastric&neurons:&
(Marder$and$Bucher$2007)$
0.6$
2. Block persistent sodium current (INaP) using Riluzole
• Ventricular$dilator$(VD)$
0.8$
• Inferior$cardiac$(IC)$
(Marder'&'Bucher'2007)'
0.8$
CsCl'
Unblock' Recover'
(25,30mM)'
Pyloric$rhythm$ Gastric$rhythm$
• Anterior$burster$(AB)$
1.2$
• Pyloric&dilator&(PD)&
• Lateral&pyloric&(LP)&
1$
• Pyloric$(PY)$
H.#americanus#
C.#borealis#
1$
1$
Control'
1.6$
1)$synapLc$inputs$
2)$neuromodulators$
1.2$
0$
Pyloric&neurons:&
1.4$
Methods
1.4$
1.2$
0$
0.6$
The stomatogastric ganglion (STG) in the American lobster is
50 µM Riluzole
composed of approximately 30 identifiable neurons (5). The STG
0.4$
has both a pyloric and a gastric motor pattern generating network.
0.2$
The type and the distribution of different ionic current channels
0$
define the intrinsic electric properties of each type of neuron. IA
Pyloric'Rhythm' Gastric'Rhythm'
affects the rate of post inhibitory rebound(1). INaP initiates and
Control$
Riluzole$50μM$
Recover$
maintains firing activities (2). Ih initiates bursting (3). ICAN
maintains the plateau potential (2). However, less is known about
how the ionic currents contribute to the distinguishable oscillatory
3. Block transient potassium current (IA) using 4AP
rhythms between the pyloric neurons
and gastric neurons.
Effects'of'4AP'on'pyloric'neurons' B
A
Slow$and$fast$oscillaLng$networks$in$the$STG$
• $Central$paUern$generators$$
• $Modulated$by$
A
gastric'rhythms'at'100'mM'
**$
1.2$
1. Block calcium activated non-selective cationic current (ICAN) using FFA
C CsCl'blcoks'both'pyloric'and'
Control
Cycle'Frequency'(Hz)'
**$
1.4$
B
Cycle'Frequency'(Hz)'
Effects'of'CsCl'at'low'dosage'
A
Cycle'Frequency'(Hz)'
Introduction
1. Block hyper-polarization activated inward current (Ih) using CsCl
Cycle'Frequency'(Hz)'
Transmembrane ionic currents underlie the generation of
rhythmic motor output patterns. My research is to use
electrophysiological methods to study the relative role of
different ionic currents in the production of the bursting rhythms
by lobster neurons. I use the stomatogastric ganglion (STG) in the
American lobster as my model system because it’s a simple
neural network that generates the slow (~0.1Hz) gastric and fast
(~1Hz) pyloric rhythms with uniquely identifiable neurons through
different network mechanisms. I investigated the functions of
transient potassium current (IA), persistent sodium current (INaP),
calcium activated non-selective cationic current (ICAN) and hyperpolarization activated inward current (Ih) in 4 pyloric neurons
(pyloric dilator (PD), pyloric (PY), lateral pyloric (LP), and ventral
dilator (VD)) and 3 gastric neurons (lateral gastric (LG), medial
gastric (MG), and gastric mill (GM)). My results demonstrate that
1) Both gastric and pyloric neurons express all four investigated
ionic currents 2) Blocking IA selectively activated the gastric
rhythm 3) INaP, ICAN and Ih are necessary for maintaining both the
gastric and pyloric rhythms; the gastric rhythms were enhanced
when Ih channels were unblocked.
Results Continued
Cycle'Frequency'(Hz)'
Abstract
pdn(V)
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as a linear function of shal gene expression in identified stomatogastric neurons. The Journal of neuroscience :
the official journal of the Society for Neuroscience 17, 6597-6610 (1997).
Harris-Warrick, R. M. Voltage-sensitive ion channels in rhythmic motor systems. Current opinion in neurobiology
12, 646-651 (2002).
Kiehn, O. & Harris-Warrick, R. M. 5-HT modulation of hyperpolarization-activated inward current and calciumdependent outward current in a crustacean motor neuron. Journal of neurophysiology 68, 496-508 (1992).
Marder, E. & Bucher, D. Understanding circuit dynamics using the stomatogastric nervous system of lobsters and
crabs. Annual review of physiology 69, 291-316, doi:10.1146/annurev.physiol.69.031905.161516 (2007).
Selverston, A. I., Russell, D. F. & Miller, J. P. The stomatogastric nervous system: structure and function of a small
neural network. Progress in neurobiology 7, 215-290 (1976).
Acknowledgements
I thank Dr. Allen Selverston and my thesis advisor Dr. Joseph Ayers for their advice and
direction in this work.