Red Pigment Concentrating Hormone Strongly Enhances the Strength of the Feedback to the Pyloric Rhythm Oscillator But Has Little Effect on Pyloric Rhythm Period

2006 ◽  
Vol 95 (3) ◽  
pp. 1762-1770 ◽  
Author(s):  
Vatsala Thirumalai ◽  
Astrid A. Prinz ◽  
Christian D. Johnson ◽  
Eve Marder
Keyword(s):  
Normal Saline ◽  
Homarus Americanus ◽  
Operating Conditions ◽  
Cycle Period ◽  
Dynamic Clamp ◽  
Red Pigment ◽  
Response Curves ◽  
Pyloric Network ◽  
Pyloric Dilator ◽  
Pyloric Rhythm

The neuropeptide, red pigment concentrating hormone (RPCH), strengthened the inhibitory synapse from the lateral pyloric (LP) neuron to the pyloric dilator (PD) neurons in the pyloric network of the stomatogastric ganglion (STG) of the lobster, Homarus americanus. RPCH produced several-fold increases in the amplitude of both action potential–mediated and non–impulse-mediated transmission that persisted for as long as the peptide remained present. Because the LP to PD synapse is the only feedback to the pacemaker kernel of the pyloric network, which consists of the electrically coupled two PD neurons and the anterior burster (AB) neuron, it might have been expected that strengthening the LP to PD synapse would increase the period of the pyloric rhythm. However, the period of the pyloric rhythm increased only transiently in RPCH, and a transient increase in cycle period was observed even when the LP neuron was hyperpolarized. Phase response curves were measured using the dynamic clamp to create artificial inhibitory inputs of variable strength and duration to the PD neurons. Synaptic conductance values seen in normal saline were ineffective at changing the pyloric period throughout the pyloric cycle. Conductances similar to those seen in 10−6 M RPCH also did not evoke phase resets at phases when the LP neuron is typically active. Thus the dramatic effects of RPCH on synaptic strength have little role in modulation of the period of the pyloric rhythm under normal operating conditions but may help to stabilize the rhythm when the cycle period is too slow or too fast.

scholarly journals Differential Modulation of Synaptic Strength and Timing Regulate Synaptic Efficacy in a Motor Network

2011 ◽  
Vol 105 (1) ◽  
pp. 293-304 ◽  
Author(s):  
Bruce R. Johnson ◽  
Jessica M. Brown ◽  
Mark D. Kvarta ◽  
Jay Y. J. Lu ◽  
Lauren R. Schneider ◽  
...  
Keyword(s):  
Synaptic Input ◽  
Synaptic Strength ◽  
Neuronal Firing ◽  
Cycle Period ◽  
Cycle Frequency ◽  
Pyloric Network ◽  
Motor Network ◽  
Pyloric Dilator ◽  
Network Output ◽  
Firing Properties

Neuromodulators modify network output by altering neuronal firing properties and synaptic strength at multiple sites; however, the functional importance of each site is often unclear. We determined the importance of monoamine modulation of a single synapse for regulation of network cycle frequency in the oscillatory pyloric network of the lobster. The pacemaker kernel of the pyloric network receives only one chemical synaptic feedback, an inhibitory synapse from the lateral pyloric (LP) neuron to the pyloric dilator (PD) neurons, which can limit cycle frequency. We measured the effects of dopamine (DA), octopamine (Oct), and serotonin (5HT) on the strength of the LP→PD synapse and the ability of the modified synapse to regulate pyloric cycle frequency. DA and Oct strengthened, whereas 5HT weakened, LP→PD inhibition. Surprisingly, the DA-strengthened LP→PD synapse lost its ability to slow the pyloric oscillations, whereas the 5HT-weakened LP→PD synapse gained a greater influence on the oscillations. These results are explained by monoamine modulation of factors that determine the firing phase of the LP neuron in each cycle. DA acts via multiple mechanisms to phase-advance the LP neuron into the pacemaker's refractory period, where the strengthened synapse has little effect. In contrast, 5HT phase-delays LP activity into a region of greater pacemaker sensitivity to LP synaptic input. Only Oct enhanced LP regulation of cycle period simply by enhancing LP→PD synaptic strength. These results show that modulation of the strength and timing of a synaptic input can differentially affect the synapse's efficacy in the network.

Amine Modulation of Ih in a Small Neural Network

2006 ◽  
Vol 96 (6) ◽  
pp. 2931-2940 ◽  
Author(s):  
Jack H. Peck ◽  
Eric Gaier ◽  
Erin Stevens ◽  
Sarah Repicky ◽  
Ronald M. Harris-Warrick
Keyword(s):  
Functional Role ◽  
Cycle Period ◽  
Slow Time ◽  
Maximal Conductance ◽  
Small Current ◽  
Inward Current ◽  
Pyloric Network ◽  
Bath Application ◽  
Slow Time Constant ◽  
Pyloric Rhythm

We studied the functional role and modulation of the hyperpolarization-activated inward current ( Ih) in the pyloric network of the lobster stomatogastric ganglion. In isolated neurons, Ih is a small current with a hyperpolarized voltage of half-activation ( VAct) and a slow time constant of activation (τAct). Bath application of dopamine (DA), octopamine (OCT), or serotonin (5HT) modified Ih in selected synaptically isolated pyloric neurons. DA significantly enhanced Ih in the anterior burster (AB) neuron by depolarizing its VAct, accelerating its τAct, and enhancing its maximal conductance ( gmax). DA more weakly enhanced Ih in the pyloric constrictor (PY) and ventricular dilator (VD) neurons. OCT weakly depolarized VAct and accelerated τAct in the VD and inferior cardiac (IC) neurons. 5HT depolarized VAct in the IC neuron. Under control conditions with intact modulatory inputs from other ganglia, the pyloric rhythm cycles strongly at about 1–2 Hz. Bath application of the Ih blocker cesium (Cs+) caused a mean increase in the period of 8%, although this effect was highly variable. When Cs+ was applied to an isolated ganglion where the pyloric rhythm had been activated only by DA, the cycle period was consistently increased by 13.5%, with no other strong changes in rhythm parameters. These results suggest that Ih regulates the pyloric rhythm by accelerating AB pacemaker frequency, but that this effect can vary with the modulatory conditions.

Pharmacological dissection of pyloric network of the lobster stomatogastric ganglion using picrotoxin

1980 ◽  
Vol 44 (6) ◽  
pp. 1089-1101 ◽  
Author(s):  
M. Bidaut
Keyword(s):  
Stomatogastric Ganglion ◽  
Inhibitory Synapses ◽  
Primary Role ◽  
Panulirus Interruptus ◽  
Pyloric Network ◽  
Pyloric Dilator ◽  
Fast Rise ◽  
Later Phase ◽  
Pyloric Rhythm

1. Picrotoxin (PTX) (10(-7)-10(-6) M) completely blocked most inhibitory synapses in the pyloric pattern generator of the lobster (Panulirus interruptus) stomatogastric ganglion. The sensitivity of synapses from most classes of identified neurons was examined. Blockade was at least partly reversible with prolonged washing. 2. The synapses from pyloric dilator (PD) neurons were the only inhibitory synapses that picrotoxin failed to block completely. 3. A correlation is derived that brief, fast-rise inhibitory postsynaptic potentials (IPSPs) are picrotoxin sensitive, whereas a slow rounded component of IPSPs from PD neurons is not picrotoxin sensitive. 4. Picrotoxin caused specific changes in the pattern of the motor rhythm produced by the 16-cell pyloric network. This sheds some light on the functional role of particular synapses in the pyloric generator. 5. The endogenously bursting neurons (PD and anterior burster (AB)), which drive the pyloric rhythm, kept a similar burst rate. 6. Under picrotoxin, the pyloric "follower" neurons all moved to later phase relative to the "driver" group. Some normally antagonistic cells, related by reciprocal inhibitor connections, became in-phase. These and other pattern changes could be related to blockade of particular synapses. 7. The pyloric rhythm was still quite recognizable under picrotoxin despite the drastically altered circuitry of the synaptic network. This supports the idea that periodic inhibition from the PD driver neurons plays a primary role in creating the pyloric pattern.

Target-Specific Short-Term Dynamics Are Important for the Function of Synapses in an Oscillatory Neural Network

2005 ◽  
Vol 94 (4) ◽  
pp. 2590-2602 ◽  
Author(s):  
Akira Mamiya ◽  
Farzan Nadim
Keyword(s):  
Spiny Lobster ◽  
Synaptic Depression ◽  
The Other ◽  
Cycle Period ◽  
Main Function ◽  
Short Term ◽  
Presynaptic Neuron ◽  
Pyloric Network ◽  
Pyloric Dilator ◽  
Oscillatory Neural Network

Short-term dynamics such as facilitation and depression are present in most synapses and are often target-specific even for synapses from the same type of neuron. We examine the dynamics and possible functions of two synapses from the same presynaptic neuron in the rhythmically active pyloric network of the spiny lobster. Using simultaneous recordings, we show that the synapses from the lateral pyloric (LP) neuron to the pyloric dilator (PD; a member of the pyloric pacemaker ensemble) and the pyloric constrictor (PY) neurons both show short-term depression. However, the postsynaptic potentials produced by the LP-to-PD synapse are larger in amplitude, depress less, and recover faster than those produced by the LP-to-PY synapse. The main function of the LP-to-PD synapse is to slow down the pyloric rhythm. However, in some cases, it slows down the rhythm only when it is fast and has no effect or to speeds up when it is slow. In contrast, the LP-to-PY synapse functions to delay the activity of the PY neuron; this delay increases as the cycle period becomes longer. Using a computational model, we show that the short-term dynamics of synaptic depression observed for each of these synapses are tailored to their individual functions and that replacing the dynamics of either synapse with the other would disrupt these functions. Together, the experimental and modeling results suggest that the target-specific features of short-term synaptic depression are functionally important for synapses efferent from the same presynaptic neuron.

scholarly journals A Neuronal Role For a Crustacean Red Pigment Concentrating Hormone-Like Peptide: Neuromodulation of the Pyloric Rhythm in the Crab, Cancer Borealis

1988 ◽  
Vol 135 (1) ◽  
pp. 165-181 ◽  
Author(s):  
MICHAEL P. NUSBAUM ◽  
EVE MARDER
Keyword(s):  
Nervous System ◽  
Physiological Data ◽  
Red Pigment ◽  
Stomatogastric Nervous System ◽  
Cancer Borealis ◽  
Cycle Frequency ◽  
Pyloric Dilator ◽  
Whole Mount ◽  
Motor Neurones ◽  
Pyloric Rhythm

The distribution of red pigment concentrating hormone (RPCH)-like immunoreactivity (RPLI) in the stomatogastric nervous system of the crab, Cancer borealis, was studied using whole-mount immunocytochemistry. RPLI was seen in neuropilar processes in the stomatogastric ganglion (STG), and in somata in the oesophageal ganglion and commissural ganglia. Staining was blocked by preincubating the antiserum with RPCH, as well as with a number of adipokinetic hormones (AKHs) and related peptides. Synthetic RPCH had strong actions on the pyloric rhythm of the isolated STG. Bath applications of RPCH (10−9-10−6moll−1) increased the cycle frequency in preparations displaying slow pyloric rhythms, and initiated rhythmic pyloric activity in silent preparations. In the presence of tetrodotoxin (TTX), RPCH evoked rhythmic non-impulse-mediated alternations in membrane potential in the lateral pyloric and pyloric dilator motor neurones. The effects of RPCH were compared to those of a series of AKHs which resemble RPCH structurally. The immunocytochemical and physiological data together suggest that RPCH or a similar molecule is a neurally released modulator of the STG.

EFFECTS OF INCREASING DOSES OF PYROGLUTAMYL-HISTIDYL-PROLINE AMIDE ON SERUM THYROTROPHIN LEVELS IN NORMAL SUBJECTS

1972 ◽  
Vol 70 (1) ◽  
pp. 196-208 ◽  
Author(s):  
Bengt Karlberg ◽  
Sven Almqvist
Keyword(s):  
Normal Saline ◽  
Standard Dose ◽  
Normal Subjects ◽  
Response Curves ◽  
Clinical Observations ◽  
Trh Stimulation ◽  
Stimulation Tests ◽  
Serial Measurements ◽  
Serum Tsh ◽  
Stimulation Of

ABSTRACT The effects of the administration of normal saline in four normal subjects and the single iv injections of synthetic pyroglutamyl-histidyl-proline amide (TRH) in doses of 6.25, 12.5, 25, 50, 100, 200 and 400 μg in 12 healthy subjects were evaluated by clinical observations and serial measurements from −10 to + 360 minutes of serum TSH, PBI, STH, cholesterol, glucose and insulin. Normal saline and TRH 6.25 μg iv did not change the serum TSH level. The minimum iv dose of TRH increasing serum TSH within 10 minutes was 12.5 μg. Nine of 12 subjects gave maximal increases of serum TSH after TRH 100 μg and all after 200 and 400 μg. The time for the peak response varied with the dose from 15 to 60 minutes. The dose-response curves, average and individual, were complex and not linear. This was interpreted as a varying degree of stimulation of both pituitary synthesis and release of TSH by TRH. PBI changes were measured at 2 h and 6 h. Minimum dose for a significant increase of PBI was 12.5 μg and 6.25 μg of TRH for the respective times. No change in basal STH-levels occurred in 53 of 65 TRH-stimulation tests. Nine of the 12 changes in serum STH occurred in four subjects with varying basal STH-levels. No changes were found in serum cholesterol, glucose or insulin. Our results show that 50 μg of TRH can be used as a standard dose for the single iv stimulation of pituitary release of TSH. TRH stimulated both TSH and STH release in 18% of our tests.

Dopamine Modulation of Calcium Currents in Pyloric Neurons of the Lobster Stomatogastric Ganglion

2003 ◽  
Vol 90 (2) ◽  
pp. 631-643 ◽  
Author(s):  
Bruce R. Johnson ◽  
Peter Kloppenburg ◽  
Ronald M. Harris-Warrick
Keyword(s):  
Calcium Channel ◽  
Transmitter Release ◽  
Stomatogastric Ganglion ◽  
Calcium Currents ◽  
Voltage Gated ◽  
Pyloric Network ◽  
Pyloric Dilator ◽  
Voltage Dependent ◽  
Inward Currents ◽  
Dopamine Modulation

We examined the dopamine (DA) modulation of calcium currents (ICa) that could contribute to the plasticity of the pyloric network in the lobster stomatogastric ganglion. Pyloric somata were voltage-clamped under conditions designed to block voltage-gated Na+, K+, and H currents. Depolarizing steps from –60 mV generated voltage-dependent, inward currents that appeared to originate in electrotonically distal, imperfectly clamped regions of the cell. These currents were blocked by Cd2+ and enhanced by Ba2+ but unaffected by Ni2+. Dopamine enhanced the peak ICa in the pyloric constrictor (PY), lateral pyloric (LP), and inferior cardiac (IC) neurons and reduced peak ICa in the ventricular dilator (VD), pyloric dilator (PD), and anterior burster (AB) neurons. All of these effects, except for the AB, are consistent with DA's excitation or inhibition of firing in the pyloric neurons. Enhancement of ICa in PY and LP neurons and reduction of ICa in VD and PD neurons are also consistent with DA-induced synaptic strength changes via modulation of presynaptic ICa. However, the reduction of ICa in AB suggests that DA's enhancement of AB transmitter release is not directly mediated through presynaptic ICa. ICa in PY and PD neurons was more sensitive to nifedipine block than in AB neurons. In addition, nifedipine blocked DA's effects on ICa in the PY and PD neurons but not in the AB neuron. Thus the contribution of specific calcium channel subtypes carrying the total ICa may vary between pyloric neuron classes, and DA may act on different calcium channel subtypes in the different pyloric neurons.

scholarly journals Episodic Bouts of Activity Accompany Recovery of Rhythmic Output By a Neuromodulator- and Activity-Deprived Adult Neural Network

2003 ◽  
Vol 90 (4) ◽  
pp. 2720-2730 ◽  
Author(s):  
Jason A. Luther ◽  
Alice A. Robie ◽  
John Yarotsky ◽  
Christopher Reina ◽  
Eve Marder ◽  
...  
Keyword(s):  
Neural Network ◽  
Neuronal Network ◽  
Recovery Process ◽  
Stomatogastric Ganglion ◽  
Cancer Borealis ◽  
Pyloric Network ◽  
Underlying Mechanisms ◽  
Over Time ◽  
Phase Relationships ◽  
Pyloric Rhythm

The pyloric rhythm of the stomatogastric ganglion of the crab, Cancer borealis, slows or stops when descending modulatory inputs are acutely removed. However, the rhythm spontaneously resumes after one or more days in the absence of neuromodulatory input. We recorded continuously for days to characterize quantitatively this recovery process. Activity bouts lasting 40–900 s began several hours after removal of neuromodulatory input and were followed by stable rhythm recovery after 1–4 days. Bout duration was not related to the intervals (0.3–800 min) between bouts. During an individual bout, the frequency rapidly increased and then decreased more slowly. Photoablation of back-filled neuromodulatory terminals in the stomatogastric ganglion (STG) neuropil had no effect on activity bouts or recovery, suggesting that these processes are intrinsic to the STG neuronal network. After removal of neuromodulatory input, the phase relationships of the components of the triphasic pyloric rhythm were altered, and then over time the phase relationships moved toward their control values. Although at low pyloric rhythm frequency the phase relationships among pyloric network neurons depended on frequency, the changes in frequency during recovery did not completely account for the change in phase seen after rhythm recovery. We suggest that activity bouts represent underlying mechanisms controlling the restructuring of the pyloric network to allow resumption of an appropriate output after removal of neuromodulatory input.

Long-Term Expression of Two Interacting Motor Pattern-Generating Networks in the Stomatogastric System of Freely Behaving Lobster

1998 ◽  
Vol 79 (3) ◽  
pp. 1396-1408 ◽  
Author(s):  
Stefan Clemens ◽  
Denis Combes ◽  
Pierre Meyrand ◽  
John Simmers
Keyword(s):  
Motor Neurons ◽  
Motor Pattern ◽  
Burst Duration ◽  
Cycle Period ◽  
Gastric Mill ◽  
Pyloric Network ◽  
Freely Behaving ◽  
Stomatogastric System

Clemens, Stefan, Denis Combes, Pierre Meyrand, and John Simmers. Long-term expression of two interacting motor pattern-generating networks in the stomatogastric system of freely behaving lobster. J. Neurophysiol. 79: 1396–1408, 1998. Rhythmic movements of the gastric mill and pyloric regions of the crustacean foregut are controlled by two stomatogastric neuronal networks that have been intensively studied in vitro. By using electromyographic recordings from the European lobster, Homarus gammarus, we have monitored simultaneously the motor activity of pyloric and gastric mill muscles for ≤3 mo in intact and freely behaving animals. Both pyloric and gastric mill networks are almost continuously active in vivo regardless of the presence of food. In unfed resting animals kept under “natural-like” conditions, the pyloric network expresses the typical triphasic pattern seen in vitro but at considerably slower cycle periods (2.5–3.5 s instead of 1–1.5 s). Gastric mill activity occurs at mean cycle periods of 20–50 s compared with 5–10 s in vitro but may suddenly stop for up to tens of minutes, then restart without any apparent behavioral reason. When conjointly active, the two networks express a strict coupling that involves certain but not all motor neurons of the pyloric network. The posterior pyloric constrictor muscles, innervated by a total of 8 pyloric (PY) motor neurons, are influenced by the onset of each gastric mill medial gastric/lateral gastric(MG/LG) neuron powerstroke burst, and for one cycle, PY neuron bursts may attain >300% of their mean duration. However, the duration of activity in the lateral pyloric constrictor muscle, innervated by the unique lateral pyloric (LP) motor neuron, remains unaffected by this perturbation. During this period after gastric perturbation, LP neuron and PY neurons thus express opposite burst-to-period relationships in that LP neuron burst duration is independent of the ongoing cycle period, whereas PY neuron burst duration changes with period length. In vitro the same type of gastro-pyloric interaction is observed, indicating that it is not dependent on sensory inputs. Moreover, this interaction is intrinsic to the stomatogastric ganglion itself because the relationship between the two networks persists after suppression of descending inputs to the ganglion. Intracellular recordings reveal that thisgastro-pyloric interaction originates from the gastric MG and LG neurons of the gastric network, which inhibit the pyloric pacemaker ensemble. As a consequence, the pyloric PY neurons, which are inhibited by the pyloric dilator (PD) neurons of the pyloric pacemaker group, extend their activity during the time that PD neuron is held silent. Moreover, there is evidence for a pyloro-gastric interaction, apparently rectifying, from the pyloric pacemakers back to the gastric MG/LG neuron group.

scholarly journals Electrical coupling and innexin expression in the stomatogastric ganglion of the crabCancer borealis

2014 ◽  
Vol 112 (11) ◽  
pp. 2946-2958 ◽  
Author(s):  
Sonal Shruti ◽  
David J. Schulz ◽  
Kawasi M. Lett ◽  
Eve Marder
Keyword(s):  
Sequence Similarity ◽  
Electrical Coupling ◽  
Homarus Americanus ◽  
Stomatogastric Ganglion ◽  
Electrical Synapse ◽  
Coupling Coefficients ◽  
Cancer Borealis ◽  
Electrophysiological Recordings ◽  
Pyloric Dilator ◽  
Lateral Posterior

Gap junctions are intercellular channels that allow for the movement of small molecules and ions between the cytoplasm of adjacent cells and form electrical synapses between neurons. In invertebrates, the gap junction proteins are coded for by the innexin family of genes. The stomatogastric ganglion (STG) in the crab Cancer borealis contains a small number of identified and electrically coupled neurons. We identified Innexin 1 ( Inx1), Innexin 2 (Inx2), Innexin 3 (Inx3), Innexin 4 ( Inx4), Innexin 5 (Inx5), and Innexin 6 ( Inx6) members of the C. borealis innexin family. We also identified six members of the innexin family from the lobster Homarus americanus transcriptome. These innexins show significant sequence similarity to other arthropod innexins. Using in situ hybridization and reverse transcriptase-quantitative PCR (RT-qPCR), we determined that all the cells in the crab STG express multiple innexin genes. Electrophysiological recordings of coupling coefficients between identified pairs of pyloric dilator (PD) cells and PD-lateral posterior gastric (LPG) neurons show that the PD-PD electrical synapse is nonrectifying while the PD-LPG synapse is apparently strongly rectifying.

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