Research: The Neural Origins ofBreathing Systems Neuroscience · Systems Neuroscience laboratory in...
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Systems Neuroscience The College of Wi iiiam and Mary The most important issues in contemporary biology are interdisciplinary, spanning multiple levels of analysis from genes and molecules to the complex properties of networks. Nowhere is the interdisciplinary nature of modern-day life sciences more relevant than in neuroscience. Brain function underlies the vast repertoire of human behaviors and dysfunction of the brain and central nervous system causes many of society's most serious health problems. I am Professor Christopher A. Del Negro and my Systems Neuroscience laboratory in the Department of Applied Science provides a unique environment for neuroscience research and training at the graduate and postdoctoral level. My team and I have assembled state-of-the art experimental workstations for intracellular and patch-clamp electrophysiology combined with in vitro live-cell videomicroscopy and fluorescence imaging. We also have a vigorous computational neuroscience branch; we support parallel computing facilities for modeling and simulation. Our strategy to elucidate new knowledge in neuroscience blends theory and experiment: we use modeling to generate testable predictions, which are systematically evaluated via hypothesis- driven experimental studies. The masters and doctoral degree programs in Applied Science offer flexible curricula that are individually tailored by students, in consultation with their faculty advisors, to accomplish each student's unique and often interdisciplinary educational goals. Research: The Neural Origins of Breathing Breathing behavior in mammals begins in utero and continues without lapse for the entire lifespan of the animal, which in humans can last up to, or exceed, 100 years. Diseases that affect the neural control of breathing can strike at any age, but newborns and premature babies are particularly susceptible to various forms of apnea and SIDS. We aim to provide new knowledge about how the neurons, synapses and networks of the brain stem assemble the rhythm-generating systems that drive breathing movements and control respiratory physiology. Breathing is an especially advantageous model system for this type of analysis because it is a behavior that can be studied under controlled conditions in vitro, using reduced brain stem 'slice' preparations. Our 'breathing slices' retain functional respiratory networks and generate spontaneous motor output during the inspiratory phase of the respiratory cycle. In mammals, the rhythm for breathing originates in the brain stem nucleus called the preBotzinger Complex (preBotC). We isolate the preBotC and .A B 110 mV Figure 1. The 'breathing slice' preparation in vitro. its constituent rhythmogenic neurons in slice preparations (Fig. 1A). Rhythmic inspiratory motor activity can be measured via the hypoglossal cranial nerve output (Xlln) in vitro, while we examine cellular and synaptic properties in the context of network function. During fictive inspiration, neurons in the preBotC generate robust bursts coincident with XII motor output (Fig. 1B). We aim to discover the cellular and synaptic mechanisms that produce rhythmic inspiratory bursts in preBotC neurons. Figure 2. Students and faculty work together, using cutting-edge technology, to discover new principles in neuroscience at The College of William and Mary. One ongoing project in the laboratory examines calcium-activated nonspecific cationic membrane currents (i.e., ' CAN )' The ion channels underlying 'CAN are putatively from the transient receptor potential, or TRP, superfamily and have the unique ability to integrate voltage-dependent calcium influx with synaptically activated intracellular calcium release mechanisms. TRP channels can transform these Figure 3. Two preBotC neurons recorded in vitro using patch-clamp and fluorescent calcium imaging. convergent calcium signals into high-amplitude, long-lasting neuronal activity states, which are suitable for driving inspiratory bursts and rhythm generation. Another thrust of our research examines the patterns of network connectivity among preBotC neurons. Here we use dual intracellular recordings to quantify synaptic coupling between preBotC neurons, as well as epifluorescence, confocal, and
Transcript of Research: The Neural Origins ofBreathing Systems Neuroscience · Systems Neuroscience laboratory in...
Systems Neuroscience
The College of Wi iiiam and Mary
The most important issues in contemporarybiology are interdisciplinary, spanning multiple
levels of analysis fromgenes and molecules tothe complex properties ofnetworks. Nowhere is theinterdisciplinary nature ofmodern-day life sciencesmore relevant than inneuroscience. Brainfunction underlies the vastrepertoire of humanbehaviors and dysfunction
of the brain and central nervous system causesmany of society's most serious health problems.
I am Professor Christopher A. Del Negro and mySystems Neuroscience laboratory in theDepartment of Applied Science provides a uniqueenvironment for neuroscience research andtraining at the graduate and postdoctoral level. Myteam and I have assembled state-of-the artexperimental workstations for intracellular andpatch-clamp electrophysiology combined with invitro live-cell videomicroscopy and fluorescenceimaging. We also have a vigorous computationalneuroscience branch; we support parallelcomputing facilities for modeling and simulation.Our strategy to elucidate new knowledge inneuroscience blends theory and experiment: weuse modeling to generate testable predictions,which are systematically evaluated via hypothesis-driven experimental studies.
The masters and doctoral degree programs inApplied Science offer flexible curricula that areindividually tailored by students, in consultationwith their faculty advisors, to accomplish eachstudent's unique and often interdisciplinaryeducational goals.
Research: The Neural Origins of BreathingBreathing behavior in mammals begins in uteroand continues without lapse for the entire lifespanof the animal, which in humans can last up to, orexceed, 100 years. Diseases that affect the neuralcontrol of breathing can strike at any age, butnewborns and premature babies are particularlysusceptible to various forms of apnea and SIDS.We aim to provide new knowledge about how theneurons, synapses and networks of the brain stemassemble the rhythm-generating systems thatdrive breathing movements and control respiratoryphysiology.
Breathing is an especially advantageous modelsystem for this type of analysis because it is abehavior that can be studied under controlledconditions in vitro, using reduced brain stem 'slice'preparations. Our 'breathing slices' retainfunctional respiratory networks and generatespontaneous motor output during the inspiratoryphase of the respiratory cycle.
In mammals, the rhythm for breathing originates inthe brain stem nucleus called the preBotzingerComplex (preBotC). We isolate the preBotC and.A B
110 mV
Figure 1. The 'breathing slice' preparation in vitro.
its constituent rhythmogenic neurons in slicepreparations (Fig. 1A). Rhythmic inspiratory motoractivity can be measured via the hypoglossalcranial nerve output (Xlln) in vitro, while weexamine cellular and synaptic properties in thecontext of network function.
During fictive inspiration, neurons in the preBotCgenerate robust bursts coincident with XII motoroutput (Fig. 1B). We aim to discover the cellularand synaptic mechanisms that produce rhythmicinspiratory bursts in preBotC neurons.
Figure 2. Students and faculty work together, usingcutting-edge technology, to discover new principlesin neuroscience at The College of William and Mary.
One ongoing project in the laboratory examinescalcium-activated nonspecific cationic membranecurrents (i.e., 'CAN)' The ion channels underlying 'CAN
are putatively from the transient receptor potential,or TRP, superfamily and have the unique ability tointegrate voltage-dependent calcium influx withsynaptically activated intracellular calcium releasemechanisms. TRP channels can transform these
Figure 3. Two preBotC neurons recorded in vitrousing patch-clamp and fluorescent calcium imaging.
convergent calcium signals into high-amplitude,long-lasting neuronal activity states, which aresuitable for driving inspiratory bursts and rhythmgeneration.
Another thrust of our research examines thepatterns of network connectivity among preBotCneurons. Here we use dual intracellular recordingsto quantify synaptic coupling between preBotCneurons, as well as epifluorescence, confocal, and
Figure 5. Ordinary differential equations that describemembrane potential trajectory in preBtitC neuronsduring respiratory-like network activity. These equationsare a subset of the full model.
WILLIAM&MARY
Contact
Christopher A. Del Negro, Ph.D.Department of Applied ScienceThe College of William and MaryWilliamsburg, VA 23185757 [email protected]://people.wm.edu/-cadeln/
Applied Science at William and Mary
The College of William and Mary is the secondoldest institution of higher education in the nationand has been repeatedly honored for itsexcellence by annual ran kings in US News &World Report. The Department of Applied Scienceis at the forefront of interdisciplinary research andits graduate students enjoy a flexible curriculumand yearly stipends of $20,040 plus tuition andhealth insurance. Finally, William & Mary is locatedin the town of Williamsburg, with its historicColonial village and nearby tourist attractions likethe Chesapeake bay and Atlantic beaches.
Del Negro, CA et al. (2002) Biophysical Journal82, 206-214.
Del Negro, C.A., Morgado-Valle, C., & Feldman,J.L. (2002) Neuron 34, 821-830.
Del Negro, C.A. et al. (2002) Journal ofNeurophysiology 88, 2242-2250.
Del Negro, C.A. et al. (2001) Journal ofNeurophysiology 86, 59-74.
Del Negro, C.A. et al. (1999) Journal ofNeurophysiology 81, 1478-1485.
Del Negro, C.A. et al. (1998) Biophysical Journal75,174-182.
Del Negro, C.A. & Chandler, S.H. (1998) Journal ofNeuroscience 18, 9216-9226.
Del Negro, C. A. & Chandler, S.H. (1997) Journal ofNeurophysiology 77,537-553.
This intrinsic current (lCAN) amplifies synapticexcitation and allows for the creation of robustinspiratory bursts via a positive feedback processoften called recurrent excitation, which is a form ofself-organized behavior in biology. Inspiratorybursts end once all of the preBotC neurons havebecome fully excited: this extinguishes recurrentexcitation, deactivates ,CAN' and leads to bursttermination. Some preBotC neurons spike tonicallyat low rates and subsequently restart the cycle,leading to network rhythmicity (Fig. 6). Our overallgoal is to evaluate the group-pacemakerhypothesis by determining its key mechanisms atthe cellular and synaptic level, and then usemathematical models to test and refine ourunderstanding.
Figure 6. An illustrated cycle of respiratory activityaccording to the group pacemaker hypothesis ofrhythm generation. Panels 1 - 4 show the evolution ofone inspiratory burst: from the onset of spontaneousactivity (1), to the spread of excitation through thenetwork (2-3), to the culmination of recurrentexcitation, which evokes intrinsic currents and causesa robust network-wide inspiratory burst (4).
Selected Recent PublicationsFeldman, J.L. & Del Negro, C.A. (2006) Nature
Reviews Neuroscience 7, 232-241.Del Negro, C.A. et al. (2005) Journal of
Neuroscience 25, 446-453.
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Our framework for analyzing respiratoryrhythmogenesis is the group-pacemakerhypothesis which posits that 'CAN is a dendriticallysited burst-generating current with an activationmechanism coupled to glutamatergic synapses.
multi-photon imaging to measure calciumdynamics. Calcium imaging represents aconvenient way to monitor the activity of manyneurons simultaneously, which helps revealnetwork properties such as connectivity (Fig. 3).
Figure 4. Voltage-clamp analysis of preBtitC neuronsensitivity to neuropeptides such as substance P.
Our efforts to unravel the neural basis forrespiratory rhythm also emphasize mathematicalmodeling (Fig. 5). We are developing biophysicallyrealistic models of preBotC neurons that accountfor morphology, the known complement of ionchannels in preBotC neurons, as well as the novelbiochemical signaling pathways that integratesynaptic and transmembrane calcium fluxes toevoke the burst-generating current ,CAN• Modelingat the cellular level forms the basis for networksimulations that explore the role of connectivity:both the strength of coupling and the pattern ofsynaptic interconnections in the preBotC.
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