Diverse Synaptic Connections Between Peptidergic Radula Mechanoafferent Neurons and Neurons in the Feeding System ofAplysia

2000 ◽  
Vol 83 (3) ◽  
pp. 1605-1620 ◽  
Author(s):  
Steven C. Rosen ◽  
Mark W. Miller ◽  
Colin G. Evans ◽  
Elizabeth C. Cropper ◽  
Irving Kupfermann
Keyword(s):  
Motor Neurons ◽  
Synaptic Connections ◽  
Buccal Ganglion ◽  
Motor Programs ◽  
Rhythmic Motor ◽  
Identified Neuron ◽  
Low Threshold ◽  
Sensory Responses ◽  
Fast Chemical ◽  
Spike Bursts

The buccal ganglion of Aplysia contains a heterogeneous population of peptidergic, radula mechanoafferent (RM) neurons. To investigate their function, two of the larger RM cells (B21, B22) were identified by morphological and electrophysiological criteria. Both are low-threshold, rapidly adapting, mechanoafferent neurons that responded to touch of the radula, the structure that grasps food during ingestive and egestive feeding movements. Sensory responses of the cells consisted of spike bursts at frequencies of 8–35 Hz. Each cell was found to make chemical, electrical, or combined synapses with other sensory neurons, motor neurons and interneurons involved in radula closure and/or protraction-retraction movements of the odontophore. Motor neurons receiving input included the following: B8a/b, B15, and B16, which innervate muscles contributing to radula closing; and B82, a newly identified neuron that innervates the anterodorsal region of the I1/I3 muscles of the buccal mass. B21 and B22 can affect buccal motor programs by way of their connections to interneurons such as B19 and B64. Fast, chemical, excitatory postsynaptic potentials (EPSPs) produced by RM neurons, such as B21, exhibited strong, frequency-dependent facilitation, a form of homosynaptic plasticity. Firing B21 also produced a slow EPSP in B15 that increased the excitability of the cell. Thus a sensory neuron mediating a behavioral response may have modulatory effects. The data suggest multiple functions for RM neurons including 1) triggering of phase transitions in rhythmic motor programs, 2) adjusting the force of radula closure, 3) switching from biting to swallowing or swallowing to rejection, and 4) enhancing food-induced arousal.

Afferent-Induced Changes in Rhythmic Motor Programs in the Feeding Circuitry of Aplysia

2004 ◽  
Vol 92 (4) ◽  
pp. 2312-2322 ◽  
Author(s):  
Avniel N. Shetreat-Klein ◽  
Elizabeth C. Cropper
Keyword(s):  
Sensory Neurons ◽  
Motor Neurons ◽  
Rhythmic Activity ◽  
Motor Program ◽  
Firing Frequency ◽  
Afferent Activity ◽  
Motor Programs ◽  
Rhythmic Motor ◽  
Induced Changes ◽  
The Impact

A manipulation often used to determine whether a neuron plays a role in the generation of a motor program involves injecting current into the cell during rhythmic activity to determine whether activity is modified. We perform this type of manipulation to study the impact of afferent activity on feeding-like motor programs in Aplysia. We trigger biting-like programs and manipulate sensory neurons that have been implicated in producing the changes in activity that occur when food is ingested, i.e., when bites are converted to bite-swallows. Sensory neurons that are manipulated are the radula mechanoafferent B21 and the retraction proprioceptor B51. Data suggest that both cells are peripherally activated during radula closing/retraction when food is ingested. We found that phasic subthreshold depolarization of a single sensory neuron can significantly prolong radula closing/retraction, as determined by recording both from interneurons (e.g., B64), and motor neurons (e.g., B15 and B8). Additionally, afferent activity produces a delay in the onset of the subsequent radula opening/protraction, and increases the firing frequency of motor neurons. These are the changes in activity that are seen when food is ingested. These results add to the growing data that implicate B21 and B51 in bite to bite-swallow conversions and indicate that afferent activity is important during feeding in Aplysia.

Different Roles of Neurons B63 and B34 That Are Active During the Protraction Phase of Buccal Motor Programs in Aplysia californica

1997 ◽  
Vol 78 (3) ◽  
pp. 1305-1319 ◽  
Author(s):  
Itay Hurwitz ◽  
Irving Kupfermann ◽  
Abraham J. Susswein
Keyword(s):  
Motor Neurons ◽  
Aplysia Californica ◽  
Motor Program ◽  
Excitatory Postsynaptic Potential ◽  
Strongly Correlated ◽  
Excitatory Effect ◽  
Buccal Ganglion ◽  
Motor Programs ◽  
Pattern Characteristic ◽  
Protraction Phase

Hurwitz, Itay, Irving Kupfermann, and Abraham J. Susswein. Different roles of neurons B63 and B34 that are active during the protraction phase of buccal motor programs in Aplysia californica. J. Neurophysiol. 78: 1305–1319, 1997. The buccal ganglion of Aplysia contains a central pattern generator (CPG) that organizes sequences of radula protraction and retraction during food ingestion and egestion. Neurons B63 and B34 have access to, or are elements of, the CPG. Both neurons are depolarized along with B31/B32 during the protraction phase of buccal motor programs. Both cells excite the contralateral B31/B32 neurons and inhibit B64 and other neurons active during the retraction phase. B63 and B34 also both have an axon exiting the buccal ganglia via the contralateral cerebrobuccal connective. Despite their similarities, B63 and B34 differ in a number of properties, which reflects their different functions. B63 fires during both ingestion and egestion-like buccal motor programs, whereas B34 fires only during egestion-like programs. The bilateral B63 neurons, along with the bilateral B31 and B32 neurons, act as a single functional unit. Sufficient depolarization of any of these neurons activates them all and initiates a buccal motor program. B63 is electrically coupled to both the ipsilateral and the contralateral B31/B32 neurons but monosynaptically excites the contralateral neurons with a mixed electrical and chemical excitatory postsynaptic potential (EPSP). Positive feedback caused by electrical and chemical EPSPs between B63 and B31/B32 contributes to the sustained depolarization in B31/B32 and the firing of B63 during the protraction phase of a buccal motor program. B34 is excited during the protraction phase of all buccal motor programs, but, unlike B63, it does not always reach firing threshold. The neuron fires in response to current injection only after it is depolarized for 1–2 s or after preceding buccal motor programs in which it is depolarized. Firing of B34 produces facilitating EPSPs in the contralateral B31/B32 and B63 neurons and can initiate a buccal motor program. Firing in B34 is strongly correlated with firing in the B61/B62 motor neurons, which innervate the muscle (I2) responsible for much of protraction. B34 monosynaptically excites these motor neurons. B34 firing is also correlated with firing in motor neuron B8 during the protraction phase of a buccal motor program. B8 innervates the I4 radula closer muscle, which in egestion movements is active during protraction and in ingestion movements is active during retraction. B34 has a mixed, but predominantly excitatory, effect on B8 via a slow conductance-decrease EPSP. Thus firing in B34 leads to amplification of radula protraction that is coupled with radula closing, a pattern characteristic of egestion.

Sonometric Measurements of Motor-Neuron-Evoked Movements of an Internal Feeding Structure (the Radula) in Aplysia

2001 ◽  
Vol 86 (2) ◽  
pp. 1057-1061 ◽  
Author(s):  
Irina V. Orekhova ◽  
Jian Jing ◽  
Vladimir Brezina ◽  
Ralph A. DiCaprio ◽  
Klaudiusz R. Weiss ◽  
...  
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Neural Control ◽  
Feeding System ◽  
Motor Programs ◽  
Rhythmic Motor ◽  
Feeding Structure ◽  
Intracellular Stimulation ◽  
Functional Movements ◽  
Stimulation Of

In many systems used to study rhythmic motor programs, the structures that generate behavior are at least partially internal. In these systems, it is often difficult to directly monitor neurally evoked movements. As a consequence, although motor programs are relatively well characterized, it is generally less clear how neural activity is translated into functional movements. This is the case for the feeding system of the mollusk Aplysia. Here we used sonomicrometry to monitor neurally evoked movements of the food-grasping organ in Aplysia, the radula. Movements were evoked by intracellular stimulation of motor neurons that innervate radula muscles that have been extensively studied in reduced preparations. Nevertheless our results indicate that the movements and neural control of the radula are more complex than has been assumed. We demonstrate that motor neurons previously characterized as radula openers (B48) and closers (B8, B15, B16) additionally produce other movements. Moreover, we show that the size of the movement evoked by a motor neuron can depend on the preexisting state of the radula. Specifically, the motor neurons B15 and B16 produce large closing movements when the radula is partially open but produce relatively weak closing movements in a preparation at rest. Thus the efficacy of B15 and B16 as radula closers is context dependent.

Behavioral Function of Glutamatergic Interneurons in the Feeding System of Lymnaea: Plateauing Properties and Synaptic Connections with Motor Neurons

1997 ◽  
Vol 78 (6) ◽  
pp. 3386-3395 ◽  
Author(s):  
Matthew J. Brierley ◽  
Kevin Staras ◽  
Paul R. Benjamin
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Neuron Activity ◽  
Synaptic Connections ◽  
Feeding System ◽  
Behavioral Function ◽  
Buccal Ganglion ◽  
Feeding Cycle ◽  
Symmetrical Pair ◽  
Main Component

Brierley, Matthew J., Kevin Staras, and Paul R. Benjamin. Behavioral function of glutamatergic interneurons in the feeding system of Lymnaea: plateauing properties and synaptic connections with motor neurons. J. Neurophysiol. 78: 3386–3395, 1997. Intracellular recording techniques were used to examine the electrical properties and behavioral function of a novel type of retraction phase interneuron, the N2 ventral (N2v) cells in the feeding network of the snail Lymnaea. The N2vs were compared with the previously identified N2 cells that now are renamed the N2 dorsal (N2d) cells. The N2vs are a bilaterally symmetrical pair of electrotonically coupled plateauing interneurons that are located on the ventral surfaces of the buccal ganglia. Their main axons project to the opposite buccal ganglion, but they have an additional fine process in the postbuccal nerve. N2v plateaus that outlast the duration of the stimulus can be triggered by depolarizing current pulses and prematurely terminated by applied hyperpolarizing pulses. Gradually increasing the amplitude of depolarizing pulses reveals a clear threshold for plateau initiation. N2v plateauing persists in a high Mg2+/nominally zero Ca2+ saline that blocks chemical synaptic connections, suggesting an endogenous mechanism for plateau generation. The N2vs fire sustained bursts of action potentials throughout the N2/rasp phase of the fictive feeding cycle and control the retraction phase feeding motor neurons. The N2vs excite the B3 and B9 feeding motor neurons to fire during the rasp phase of the feeding cycle. They also inhibit the B7 and B8 feeding motor neurons. The B8 cells recover from inhibition and fire during the following swallowing phase. These synaptic connections appear to be monosynaptic as they persist in high Mg2+/high Ca2+ (HiDi) saline that blocks polysynaptic pathways. Strong current-induced plateaus in the N2vs generate brief inhibitory postsynaptic responses in the B4CL rasp phase motor neurons, but this was due to the indirect N2v → N2d → B4CL pathway. The N2vs are coupled electrotonically to the N2d cells, and triggering plateau in a N2v usually induced one or two spikes in a N2d. Previous experiments showed that the N2ds generate plateau potentials during a fictive feeding cycle. Here we show that the main component of the “plateauing” waveform is due to the electrotonic coupling with the N2v cells. The differential synaptic connections of the N2v and N2d cells with retraction phase motor neurons results in a sequence of motor neuron burst activity B9 → B4CL → B8 that produces the full retraction (rasp → swallow) movements of the feeding apparatus (buccal mass). We conclude that the N2v cells are an essential component of the interneuronal network required to produce feeding motor neuron activity.

scholarly journals Low–threshold calcium spike bursts in the human thalamus

Brain ◽  
1996 ◽  
Vol 119 (2) ◽  
pp. 363-375 ◽  
Author(s):  
D. Jeanmonod ◽  
M. Magnin ◽  
A. Morel
Keyword(s):  
Human Thalamus ◽  
Low Threshold ◽  
Spike Bursts

scholarly journals Release of a single neurotransmitter from an identified interneuron coherently affects motor output on multiple time scales

2013 ◽  
Vol 109 (9) ◽  
pp. 2327-2334 ◽  
Author(s):  
Andrew M. Dacks ◽  
Klaudiusz R. Weiss
Keyword(s):  
Time Scales ◽  
Motor Program ◽  
Gaba Release ◽  
Motor Output ◽  
Multiple Time Scales ◽  
Multiple Time ◽  
Intrinsic Properties ◽  
Buccal Ganglion ◽  
Motor Programs ◽  
Pattern Characteristic

Neurotransmitters can have diverse effects that occur over multiple time scales often making the consequences of neurotransmission difficult to predict. To explore the consequences of this diversity, we used the buccal ganglion of Aplysia to examine the effects of GABA release by a single interneuron, B40, on the intrinsic properties and motor output of the radula closure neuron B8. B40 induces a picrotoxin-sensitive fast IPSP lasting milliseconds in B8 and a slow EPSP lasting seconds. We found that the excitatory effects of this slow EPSP are also mediated by GABA. Together, these two GABAergic actions structure B8 firing in a pattern characteristic of ingestive programs. Furthermore, we found that repeated B40 stimulation induces a persistent increase in B8 excitability that was occluded in the presence of the GABA B receptor agonist baclofen, suggesting that GABA affects B8 excitability over multiple time scales. The phasing of B8 activity during the feeding motor programs determines the nature of the behavior elicited during that motor program. The persistent increase in B8 excitability induced by B40 biased the activity of B8 during feeding motor programs causing the motor programs to become more ingestive in nature. Thus, a single transmitter released from a single interneuron can have consequences for motor output that are expressed over multiple time scales. Importantly, despite the differences in their signs and temporal characteristics, the three actions of B40 are coherent in that they promote B8 firing patterns that are characteristic of ingestive motor outputs.

Connections between thoraco-coxal proprioceptive afferents and motor neurons in the locust

2000 ◽  
Vol 203 (3) ◽  
pp. 435-445
Author(s):  
M. Wildman
Keyword(s):  
Electrical Stimulation ◽  
Sensory Neurons ◽  
Motor Neurons ◽  
Chordotonal Organ ◽  
Synaptic Connections ◽  
Afferent Neurons ◽  
Postsynaptic Potentials ◽  
The Common ◽  
Proprioceptive Afferents ◽  
Stimulation Of

The position of the coxal segment of the locust hind leg relative to the thorax is monitored by a variety of proprioceptors, including three chordotonal organs and a myochordotonal organ. The sensory neurons of two of these proprioceptors, the posterior joint chordotonal organ (pjCO) and the myochordotonal organ (MCO), have axons in the purely sensory metathoracic nerve 2C (N2C). The connections made by these afferents with metathoracic motor neurons innervating thoraco-coxal and wing muscles were investigated by electrical stimulation of N2C and by matching postsynaptic potentials in motor neurons with afferent spikes in N2C. Stretch applied to the anterior rotator muscle of the coxa (M121), with which the MCO is associated, evoked sensory spikes in N2C. Some of the MCO afferent neurons make direct excitatory chemical synaptic connections with motor neurons innervating the thoraco-coxal muscles M121, M126 and M125. Parallel polysynaptic pathways via unidentified interneurons also exist between MCO afferents and these motor neurons. Connections with the common inhibitor 1 neuron and motor neurons innervating the thoraco-coxal muscles M123/4 and wing muscles M113 and M127 are polysynaptic. Afferents of the pjCO also make polysynaptic connections with motor neurons innervating thoraco-coxal and wing muscles, but no evidence for monosynaptic pathways was found.

scholarly journals Functional Genetic Screen to Identify Interneurons Governing Behaviorally Distinct Aspects of Drosophila Larval Motor Programs

2016 ◽  
Author(s):  
Matt Q. Clark ◽  
Stephanie J. McCumsey ◽  
Sereno Lopez-Darwin ◽  
Ellie S. Heckscher ◽  
Chris Q. Doe
Keyword(s):  
Motor Neurons ◽  
Animal Behavior ◽  
Motor Program ◽  
Genetic Screen ◽  
Muscle Contractions ◽  
Specific Expression ◽  
Motor Programs ◽  
Secondary Screen ◽  
Forward Locomotion ◽  
Sparse Pattern

AbstractDrosophila larval crawling is an attractive system to study patterned motor output at the level of animal behavior. Larval crawling consists of waves of muscle contractions generating forward or reverse locomotion. In addition, larvae undergo additional behaviors including head casts, turning, and feeding. It is likely that some neurons are used in all these behaviors (e.g. motor neurons), but the identity (or even existence) of neurons dedicated to specific aspects of behavior is unclear. To identify neurons that regulate specific aspects of larval locomotion, we performed a genetic screen to identify neurons that, when activated, could elicit distinct motor programs. We used 165 Janelia CRM-Gal4 lines – chosen for sparse neuronal expression – to express the warmth-inducible neuronal activator TrpA1 and screened for locomotor defects. The primary screen measured forward locomotion velocity, and we identified 63 lines that had locomotion velocities significantly slower than controls following TrpA1 activation (28°C). A secondary screen was performed on these lines, revealing multiple discrete behavioral phenotypes including slow forward locomotion, excessive reverse locomotion, excessive turning, excessive feeding, immobile, rigid paralysis, and delayed paralysis. While many of the Gal4 lines had motor, sensory, or muscle expression that may account for some or all of the phenotype, some lines showed specific expression in a sparse pattern of interneurons. Our results show that distinct motor programs utilize distinct subsets of interneurons, and provide an entry point for characterizing interneurons governing different elements of the larval motor program.

Low-Threshold Monopolar Motor Mapping for Resection of Primary Motor Cortex Tumors

2012 ◽  
Vol 71 (suppl_1) ◽  
pp. ons104-ons115 ◽  
Author(s):  
Kathleen Seidel ◽  
Jürgen Beck ◽  
Lennart Stieglitz ◽  
Philippe Schucht ◽  
Andreas Raabe
Keyword(s):  
Motor Neurons ◽  
Evoked Potential ◽  
Primary Motor Cortex ◽  
Motor Evoked Potential ◽  
National Institutes Of Health ◽  
Motor Deficit ◽  
Motor Threshold ◽  
Motor Mapping ◽  
Low Threshold ◽  
A Minor

Abstract BACKGROUND: Microsurgery within eloquent cortex is a controversial approach because of the high risk of permanent neurological deficit. Few data exist showing the relationship between the mapping stimulation intensity required for eliciting a muscle motor evoked potential and the distance to the motor neurons; furthermore, the motor threshold at which no deficit occurs remains to be defined. OBJECTIVE: To evaluate the safety of low threshold motor evoked potential mapping for tumor resection close to the primary motor cortex. METHODS: Fourteen patients undergoing tumor surgery were included. Motor threshold was defined as the stimulation intensity that elicited motor evoked potentials from target muscles (amplitude > 30 μV). Monopolar high-frequency motor mapping with train-of-5 stimuli (HF-TOF; pulse duration = 500 microseconds; interstimulus interval = 4.0 milliseconds; frequency = 250 Hz) was used to determine motor response--negative sites where incision and dissection could be performed. At sites negative to 3-mA HF-TOF stimulation, the tumor was resected. RESULTS: HF-TOF mapping localized the motor neurons within the precentral gyrus by using variable, low-stimulation intensities. The lowest motor thresholds after final resection ranged from 3 to 6 mA, indicating close proximity of motor neurons. Postoperatively, 12 patients had no new motor deficit, 1 patient had a minor new temporary deficit (M4+, National Institutes of Health Stroke Scale 1), and another patient had a minor new permanent deficit (M4+, National Institutes of Health Stroke Scale 2). Thirteen patients had complete or gross total resection. CONCLUSION: These preliminary data demonstrate that a monopolar HF-TOF threshold > 3 mA was not associated with a significant new motor deficit.

Modulation of Fictive Feeding by Dopamine and Serotonin inAplysia

2000 ◽  
Vol 83 (1) ◽  
pp. 374-392 ◽  
Author(s):  
Evgeni A. Kabotyanski ◽  
Douglas A. Baxter ◽  
Susan J. Cushman ◽  
John H. Byrne
Keyword(s):  
Feeding Activity ◽  
Neural Correlates ◽  
Neural Circuitry ◽  
Pattern Generator ◽  
Synaptic Connections ◽  
Rhythmic Movements ◽  
Motor Programs ◽  
Dopaminergic Cells ◽  
Buccal Ganglia ◽  
Bath Application

The buccal ganglia of Aplysia contain a central pattern generator (CPG) that mediates rhythmic movements of the buccal apparatus during feeding. Activity in this CPG is believed to be regulated, in part, by extrinsic serotonergic inputs and by an intrinsic and extrinsic system of putative dopaminergic cells. The present study investigated the roles of dopamine (DA) and serotonin (5-HT) in regulating feeding movements of the buccal apparatus and properties of the underlying neural circuitry. Perfusing a semi-intact head preparation with DA (50 μM) or the metabolic precursor of catecholamines (l-3–4-dihydroxyphenylalanine, DOPA, 250 μM) induced feeding-like movements of the jaws and radula/odontophore. These DA-induced movements were similar to bites in intact animals. Perfusing with 5-HT (5 μM) also induced feeding-like movements, but the 5-HT-induced movements were similar to swallows. In preparations of isolated buccal ganglia, buccal motor programs (BMPs) that represented at least two different aspects of fictive feeding (i.e., ingestion and rejection) could be recorded. Bath application of DA (50 μM) increased the frequency of BMPs, in part, by increasing the number of ingestion-like BMPs. Bath application of 5-HT (5 μM) did not significantly increase the frequency of BMPs nor did it significantly increase the proportion of ingestion-like BMPs being expressed. Many of the cells and synaptic connections within the CPG appeared to be modulated by DA or 5-HT. For example, bath application of DA decreased the excitability of cells B4/5 and B34, which in turn may have contributed to the DA-induced increase in ingestion-like BMPs. In summary, bite-like movements were induced by DA in the semi-intact preparation, and neural correlates of these DA-induced effects were manifest as an increase in ingestion-like BMPs in the isolated ganglia. Swallow-like movements were induced by 5-HT in the semi-intact preparation. Neural correlates of these 5-HT-induced effects were not evident in isolated buccal ganglia, however.

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