Estimating Use-Dependent Synaptic Gain in Autonomic Ganglia by Computational Simulation and Dynamic-Clamp Analysis

2004 ◽  
Vol 92 (5) ◽  
pp. 2659-2671 ◽  
Author(s):  
Diek W. Wheeler ◽  
Paul H. M. Kullmann ◽  
John P. Horn
Keyword(s):  
Sympathetic Neurons ◽  
Computational Simulation ◽  
Sympathetic Neuron ◽  
Sympathetic Ganglia ◽  
Spike Timing ◽  
Calcium Currents ◽  
Dynamic Clamp ◽  
Autonomic Ganglia ◽  
Postsynaptic Spike ◽  
Synaptic Gain

Biological gain mechanisms regulate the sensitivity and dynamics of signaling pathways at the systemic, cellular, and molecular levels. In the sympathetic nervous system, gain in sensory-motor feedback loops is essential for homeostatic regulation of blood pressure and body temperature. This study shows how synaptic convergence and plasticity can interact to generate synaptic gain in autonomic ganglia and thereby enhance homeostatic control. Using a conductance-based computational model of an idealized sympathetic neuron, we simulated the postganglionic response to noisy patterns of presynaptic activity and found that a threefold amplification in postsynaptic spike output can arise in ganglia, depending on the number and strength of nicotinic synapses, the presynaptic firing rate, the extent of presynaptic facilitation, and the expression of muscarinic and peptidergic excitation. The simulations also showed that postsynaptic refractory periods serve to limit synaptic gain and alter postsynaptic spike timing. Synaptic gain was measured by stimulating dissociated bullfrog sympathetic neurons with 1–10 virtual synapses using a dynamic clamp. As in simulations, the threshold synaptic conductance for nicotinic excitation of firing was typically 10–15 nS, and synaptic gain increased with higher levels of nicotinic convergence. Unlike the model, gain in neurons sometimes declined during stimulation. This postsynaptic effect was partially blocked by 10 μM Cd2+, which inhibits voltage-dependent calcium currents. These results support a general model in which the circuit variations observed in parasympathetic and sympathetic ganglia, as well as other neural relays, can enable functional subsets of neurons to behave either as 1:1 relays, variable amplifiers, or switches.

scholarly journals Excitatory Muscarinic Modulation Strengthens Virtual Nicotinic Synapses on Sympathetic Neurons and Thereby Enhances Synaptic Gain

2006 ◽  
Vol 96 (6) ◽  
pp. 3104-3113 ◽  
Author(s):  
Paul H. M. Kullmann ◽  
John P. Horn
Keyword(s):  
Sympathetic Neurons ◽  
Sympathetic Ganglia ◽  
Dynamic Clamp ◽  
Neuronal Types ◽  
Synaptic Gain ◽  
Nicotinic Synapses ◽  
M1 Muscarinic ◽  
The Impact ◽  
Muscarinic Modulation ◽  
M1 Muscarinic Receptors

Acetylcholine excites many neuronal types by binding to postsynaptic m1-muscarinic receptors that signal to ion channels through the Gq/11 protein. To investigate the functional significance of this metabotropic pathway in sympathetic ganglia, we studied how muscarinic excitation modulated the integration of virtual nicotinic excitatory postsynaptic potentials (EPSPs) created in dissociated bullfrog B-type sympathetic neurons with the dynamic-clamp technique. Muscarine (1 μM) strengthened the impact of virtual synapses by reducing the artificial nicotinic conductance required to reach the postsynaptic firing threshold from 20.9 ± 5.4 to 13.1 ± 3.1 nS. Consequently, postganglionic action potential output increased by 4–215% when driven by different patterns of virtual presynaptic activity that were chosen to reflect the range of physiological firing rates and convergence levels seen in amphibian and mammalian sympathetic ganglia. In addition to inhibiting the M-type K+ conductance, muscarine activated a leak conductance in three of 37 cells. When this leak conductance was reproduced with the dynamic clamp, it also acted to strengthen virtual nicotinic synapses and enhance postganglionic spike output. Combining pharmacological M-conductance suppression with virtual leak activation, at resting potentials between −50 and −55 mV, produced synergistic strengthening of nicotinic synapses and an increase in the integrated postganglionic spike output. Together, these results reveal how muscarinic activation of a branched metabotropic pathway can enhance integration of fast EPSPs by modulating their effective strength. The results also support the hypothesis that muscarinic synapses permit faster and more accurate feedback control of autonomic behaviors by generating gain through synaptic amplification in sympathetic ganglia.

scholarly journals Satellite glia are essential modulators of sympathetic neuron survival, activity, and autonomic function

2021 ◽  
Author(s):  
Aurelia Mapps ◽  
Erica Boehm ◽  
Corinne Beier ◽  
William Thomas Keenan ◽  
Jennifer Langel ◽  
...  
Keyword(s):  
Sympathetic Neurons ◽  
Neuronal Cell ◽  
Sympathetic Neuron ◽  
Sympathetic Ganglia ◽  
Neuronal Cell Bodies ◽  
Intimate Association ◽  
Elevated Activity ◽  
Inward Rectifying Potassium Channel ◽  
Specific Deletion ◽  
Satellite Glia

Satellite glia are the major glial cells in sympathetic ganglia, enveloping neuronal cell bodies. Despite this intimate association, how satellite glia contribute to sympathetic functions remain unclear. Here, we show that satellite glia are critical for metabolism, survival, and activity of sympathetic neurons and modulate autonomic behaviors in mice. Adult ablation of satellite glia results in impaired mTOR signaling, soma atrophy, reduced noradrenergic enzymes, and loss of sympathetic neurons. However, persisting neurons have elevated activity, and satellite glia-ablated mice show increased pupil dilation and heart rate, indicative of enhanced sympathetic tone. Satellite glia-specific deletion of Kir4.1, an inward-rectifying potassium channel, largely recapitulates the cellular defects observed in glia-ablated mice, suggesting that satellite glia act in part via extracellular K+ buffering. These findings highlight neuron-satellite glia as functional units in regulating sympathetic output, with implications for disorders linked to sympathetic hyper-activity such as cardiovascular disease and hypertension.

scholarly journals Satellite glial cells modulate cholinergic transmission between sympathetic neurons

2019 ◽  
Author(s):  
Joana Enes ◽  
Surbhi Sona ◽  
Nega Gerard ◽  
Alexander C. Mitchell ◽  
Marian Haburcak ◽  
...  
Keyword(s):  
Glial Cells ◽  
Neural Control ◽  
Synapse Formation ◽  
Close Contact ◽  
Sympathetic Neurons ◽  
Cell Types ◽  
Sympathetic Neuron ◽  
Sympathetic Ganglia ◽  
Satellite Glial Cells ◽  
Satellite Glia

AbstractPostganglionic sympathetic neurons and satellite glial cells are the two major cell types of the peripheral sympathetic ganglia. Sympathetic neurons project to and provide neural control of peripheral organs and have been implicated in human disorders ranging from cardiovascular disease to peripheral neuropathies. Here we show that satellite glia regulate postnatal development and activity of sympathetic neurons, providing evidence for local ganglionic control of sympathetic drive. We show changes in the cellular architecture of the rat sympathetic ganglia during the postnatal period, with satellite glia enwrapping sympathetic neuronal somata during a period of neuronal hypertrophy. In culture, satellite glia contribute to neuronal survival, promote synapse formation and play a modulatory role in neuron-to-neuron cholinergic neurotransmission, consistent with the close contact seen within the ganglia. Cultured satellite glia make and release neurotrophins, which can partially rescue the neurons from nerve growth factor deprivation. Electrophysiological recordings and immunocytochemical analysis on cultured sympathetic neurons show that satellite glial cells influence synapse number and total neuronal activity with little effect on neuronal intrinsic excitability. Thus, satellite glia play an early and ongoing role within the postnatal sympathetic ganglia, expanding our understanding of the contributions of local and target-derived factors in the regulation of sympathetic neuron function.

The transcription factor dHAND is a downstream effector of BMPs in sympathetic neuron specification

Development ◽  
2000 ◽  
Vol 127 (18) ◽  
pp. 4073-4081 ◽  
Author(s):  
M.J. Howard ◽  
M. Stanke ◽  
C. Schneider ◽  
X. Wu ◽  
H. Rohrer
Keyword(s):  
Transcription Factor ◽  
Bone Morphogenetic Proteins ◽  
Sympathetic Neurons ◽  
Sympathetic Neuron ◽  
Sympathetic Ganglia ◽  
Catecholaminergic Neurons ◽  
Helix Loop Helix ◽  
Downstream Effector

The dHAND basic helix-loop-helix transcription factor is expressed in neurons of sympathetic ganglia and has previously been shown to induce the differentiation of catecholaminergic neurons in avian neural crest cultures. We now demonstrate that dHAND expression is sufficient to elicit the generation of ectopic sympathetic neurons in vivo. The expression of the dHAND gene is controlled by bone morphogenetic proteins (BMPs), as suggested by BMP4 overexpression in vivo and in vitro, and by noggin-mediated inhibition of BMP function in vivo. The timing of dHAND expression in sympathetic ganglion primordia, together with the induction of dHAND expression in response to Phox2b implicate a role for dHAND as transcriptional regulator downstream of Phox2b in BMP-induced sympathetic neuron differentiation.

scholarly journals HCN hyperpolarization-activated cation channels strengthen virtual nicotinic EPSPs and thereby elevate synaptic amplification in rat sympathetic neurons

2016 ◽  
Vol 116 (2) ◽  
pp. 438-447 ◽  
Author(s):  
Paul H. M. Kullmann ◽  
Kristine M. Sikora ◽  
K. Lyles Clark ◽  
Irene Arduini ◽  
Mitchell G. Springer ◽  
...  
Keyword(s):  
Voltage Clamp ◽  
Cyclic Nucleotide ◽  
Sympathetic Neurons ◽  
Reversal Potential ◽  
Hcn Channels ◽  
Dynamic Clamp ◽  
Messenger Rnas ◽  
Cation Conductance ◽  
Cervical Ganglion ◽  
Synaptic Gain

The influence of hyperpolarization-activated cation current (h-current; Ih) upon synaptic integration in paravertebral sympathetic neurons was studied together with expression of hyperpolarization-activated cyclic nucleotide-gated (HCN) subunit isoforms. All four HCN subunits were detected in homogenates of the rat superior cervical ganglion (SCG) using the PCR to amplify reverse-transcribed messenger RNAs (RT-PCR) and using quantitative PCR. Voltage clamp recordings from dissociated SCG neurons at 35°C detected Ih in all cells, with a maximum hyperpolarization-activated cation conductance of 1.2 ± 0.1 nS, half-maximal activation at −87.6 mV, and reversal potential of −31.6 mV. Interaction between Ih and synaptic potentials was tested with virtual fast nicotinic excitatory postsynaptic potentials (EPSPs) created with dynamic clamp. The blocking of Ih with 15 μM ZD7288 hyperpolarized cells by 4.7 mV and increased the virtual synaptic conductance required to stimulate an action potential from 7.0 ± 0.9 nS to 12.1 ± 0.9 nS. In response to stimulation with 40 s long trains of virtual EPSPs, ZD7288 reduced postsynaptic firing from 2.2 to 1.7 Hz and the associated synaptic amplification from 2.2 ± 0.1 to 1.7 ± 0.2. Cyclic nucleotide binding to HCN channels was simulated by blocking native Ih with ZD7288, followed by reconstitution with virtual Ih using a dynamic clamp model of the voltage clamp data. Over a 30-mV range, shifting the half-activation voltage for Ih in 10 mV depolarizing increments always increased synaptic gain. These results indicate that Ih, in sympathetic neurons, can strengthen nicotinic EPSPs and increase synaptic amplification, while also working as a substrate for cyclic nucleotide-dependent modulation.

Unusual Intranuclear Structures in Chick Sympathetic Neurons

1967 ◽  
Vol 25 ◽  
pp. 188-189
Author(s):  
E. B. Masurovsky ◽  
H. H. Benitez ◽  
M. R. Murray
Keyword(s):  
Electron Microscope ◽  
Sympathetic Neurons ◽  
Uranyl Acetate ◽  
Sympathetic Ganglia ◽  
Lead Citrate ◽  
Thin Sections ◽  
Cns Neurons ◽  
Mammalian Cns

Recent light- and electron microscope studies concerned with the effects of D2O on the development of chick sympathetic ganglia in long-term, organized culture revealed the presence of rod-like fibrillar formations, and associated granulofibrillar bodies, in the nuclei of control and deuterated neurons. Similar fibrillar formations have been reported in the nuclei of certain mammalian CNS neurons; however, related granulofibrillar bodies have not been previously described. Both kinds of intranuclear structures are observed in cultures fixed either in veronal acetate-buffered 2%OsO4 (pH 7. 4), or in 3.5% glutaraldehyde followed by post-osmication. Thin sections from such Epon-embedded cultures were stained with ethanolic uranyl acetate and basic lead citrate for viewing in the electron microscope.

Identification and characterization of mRNAs regulated by nerve growth factor in PC12 cells

1987 ◽  
Vol 7 (9) ◽  
pp. 3156-3167
Author(s):  
D G Leonard ◽  
E B Ziff ◽  
L A Greene
Keyword(s):  
Nerve Growth Factor ◽  
Growth Factor ◽  
Pc12 Cells ◽  
Time Course ◽  
Sympathetic Neuron ◽  
Sympathetic Ganglia ◽  
Cdna Libraries ◽  
Nerve Growth ◽  
Rat Tissue

Differential screening of cDNA libraries was used to detect and prepare probes for mRNAs that are regulated in PC12 rat pheochromocytoma cells by long-term (2-week) treatment with nerve growth factor (NGF). In response to NGF, PC12 cells change from a chromaffin cell-like to a sympathetic-neuron-like phenotype. Thus, one aim of this study was to identify NGF-regulated mRNAs that may be associated with the attainment of neuronal properties. Eight NGF-regulated mRNAs are described. Five of these increase 3- to 10-fold and three decrease 2- to 10-fold after long-term NGF exposure. Each mRNA was characterized with respect to the time course of the NGF response, regulation by agents other than NGF, and rat tissue distribution. Partial sequences of the cDNAs were used to search for homologies to known sequences. Homology analysis revealed that one mRNA (increased 10-fold) encodes the peptide thymosin beta 4 and a second mRNA (decreased 2-fold) encodes tyrosine hydroxylase. Another of the increased mRNAs was very abundant in sympathetic ganglia, barely detectable in brain and adrenals, and undetectable in all other tissues surveyed. One of the decreased mRNAs, by contrast, was very abundant in the adrenals and nearly absent in the sympathetic ganglia. With the exception of fibroblast growth factor, which is the only other agent known to mimic the differentiating effects of NGF on PC12 cells, none of the treatments tested (epidermal growth factor, insulin, dibutyryl cyclic AMP, dexamethasone, phorbol ester, and depolarization) reproduced the regulation observed with NGF. These and additional findings suggest that the NGF-regulated mRNAs may play roles in the establishment of the neuronal phenotype and that the probes described here will be useful to study the mechanism of action of NGF and the development and differentiation of neurons.

VSM growth is stimulated in sympathetic neuron/VSM cocultures: role of TGF-β2 and endothelin

2000 ◽  
Vol 278 (2) ◽  
pp. H404-H411 ◽  
Author(s):  
Deborah H. Damon
Keyword(s):  
Transforming Growth Factor ◽  
Sympathetic Neurons ◽  
Sympathetic Nerves ◽  
Sympathetic Neuron ◽  
Vessel Growth ◽  
Coculture Model ◽  
Transforming Growth Factor Β2 ◽  
Cervical Ganglia ◽  
Stimulation Of

Sympathetic nerves are purported to stimulate blood vessel growth. The mechanism(s) underlying this stimulation has not been determined. With use of an in vitro coculture model, the present study tests the hypothesis that sympathetic neurons stimulate the growth of vascular smooth muscle (VSM) and evaluates potential mechanisms mediating this stimulation. Sympathetic neurons isolated from superior cervical ganglia (SCG) stimulated the growth of VSM. Growth of VSM in the presence of SCG (856 ± 81%) was significantly greater than that in the absence of SCG (626 ± 66%, P < 0.05). SCG did not stimulate VSM growth in transwell cocultures. An antibody that neutralized the activity of transforming growth factor-β2 (TGF-β2) inhibited SCG stimulation of VSM growth in coculture. SCG stimulation of VSM growth was also inhibited by an endothelin A receptor antagonist. These data suggest novel mechanisms for sympathetic modulation of vascular growth that may play a role in the physiological and/or pathological growth of the vasculature.

scholarly journals The p75 Neurotrophin Receptor Mediates Neuronal Apoptosis and Is Essential for Naturally Occurring Sympathetic Neuron Death

1998 ◽  
Vol 140 (4) ◽  
pp. 911-923 ◽  
Author(s):  
Shernaz X. Bamji ◽  
Marta Majdan ◽  
Christine D. Pozniak ◽  
Daniel J. Belliveau ◽  
Raquel Aloyz ◽  
...  
Keyword(s):  
Neuronal Apoptosis ◽  
Sympathetic Neurons ◽  
Sympathetic Neuron ◽  
Neurotrophin Receptor ◽  
Tyrosine Kinase Receptor ◽  
P75 Neurotrophin Receptor ◽  
Neuron Death ◽  
Naturally Occurring ◽  
Physiological Relevance ◽  
Normal Period

Abstract. To determine whether the p75 neurotrophin receptor (p75NTR) plays a role in naturally occurring neuronal death, we examined neonatal sympathetic neurons that express both the TrkA tyrosine kinase receptor and p75NTR. When sympathetic neuron survival is maintained with low quantities of NGF or KCl, the neurotrophin brain-derived neurotrophic factor (BDNF), which does not activate Trk receptors on sympathetic neurons, causes neuronal apoptosis and increased phosphorylation of c-jun. Function-blocking antibody studies indicate that this apoptosis is due to BDNF-mediated activation of p75NTR. To determine the physiological relevance of these culture findings, we examined sympathetic neurons in BDNF−/− and p75NTR−/− mice. In BDNF−/− mice, sympathetic neuron number is increased relative to BDNF+/+ littermates, and in p75NTR−/− mice, the normal period of sympathetic neuron death does not occur, with neuronal attrition occurring later in life. This deficit in apoptosis is intrinsic to sympathetic neurons, since cultured p75NTR−/− neurons die more slowly than do their wild-type counterparts. Together, these data indicate that p75NTR can signal to mediate apoptosis, and that this mechanism is essential for naturally occurring sympathetic neuron death.

Sign in / Sign up

Export Citation Format

Share Document