The Experts below are selected from a list of 1704 Experts worldwide ranked by ideXlab platform
Hiroshi Yamagishi - One of the best experts on this subject based on the ideXlab platform.
-
identification of two cardioacceleratory neurons in the isopod crustacean ligia exotica and their effects on Cardiac Ganglion cells
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 1998Co-Authors: Akira Sakurai, Hiroshi YamagishiAbstract:We identified two pairs of cardioacceleratory (CA1, CA2) neurons in the central nervous system of the isopod Ligiaexotica and examined their effects on the Cardiac Ganglion (CG). CA1 neurons had cell bodies in the 2nd thoracic Ganglion and had arborizations in the subesophageal Ganglion and the 1st and 2nd thoracic ganglia. CA2 neurons had cell bodies in the 3rd thoracic Ganglion and had arborizations in the 2nd, 3rd and 4th thoracic ganglia. They sent axons to the heart through the ipsilateral 3rd roots of the ganglia where their cell bodies were located. Repetitive stimulation of the CA1 axon rapidly increased the burst frequency of the CG, and that of CA2 rather slowly. The increased burst rate caused by the CA1 stimulation was significantly higher than that caused by CA2. Overall depolarization of a quiescent CG cell produced by the CA1 stimulation was significantly larger in amplitude than that produced by CA2. Facilitation was obviously seen in the excitatory post-synaptic potentials evoked by the CA1 stimulation. These results show that the synaptic properties of CA1 and CA2 neurons are different, suggesting that they have different functional roles in heart regulation.
-
Isolation of Neurogenic and Myogenic Activities by Joro Spider Toxin in the Adult Heart of the Isopod Crustacean Ligia exotica
Zoological Science, 1998Co-Authors: Hiroshi Yamagishi, Akira Sakurai, Akihiko MoriAbstract:Abstract The effects of Joro spider toxin (JSTX), a specific glutamate antagonist, on the adult heart of the isopod crustacean Ligia exotica were examined. By application of JSTX, excitatory junctional potentials (EJPs) caused by the Cardiac Ganglion activity in the myocardium were gradually abolished. Subsequently, the Cardiac Ganglion and myocardium exhibited independent activities with their respective rhythms. In saline containing JSTX, no changes were observed in the muscle activity when the Ganglionic activity was changed by current injection into the Cardiac Ganglion neuron. These results indicate that two pacemaker sites, the Cardiac Ganglion and Cardiac muscle, are present in the adult heart of Ligia exotica and suggest glutamatergic neuromuscular transmission between them.
-
transfer of the heart pacemaker during juvenile development in the isopod crustacean ligia exotica
The Journal of Experimental Biology, 1997Co-Authors: Hiroshi Yamagishi, Euichi HiroseAbstract:Developmental changes in heartbeat pacemaker mechanisms were examined electrophysiologically in the isopod crustacean Ligia exotica. The heartbeat of embryos and early juveniles was myogenic. The heart muscle cells were coupled electrically, and no localized pacemaker activity was found in the heart. In newly hatched juveniles, the Cardiac Ganglion exhibited no spontaneous activity, although stimulation of the Cardiac Ganglion produced excitatory junctional potentials (EJPs) in the heart muscle. The myogenic activity of the heart was reset and entrained by the EJPs evoked by Ganglionic stimulation. During juvenile development, spontaneous EJPs appeared irregularly in the heart muscle. Later in development, the Cardiac Ganglion started rhythmic bursting, and each muscle response followed a Ganglionic burst discharge and overlapped the EJPs evoked by Ganglionic activity. At this point, the activity of the Cardiac Ganglion was suppressed by application of tetrodotoxin (TTX); however, even in old adults, both muscle activity and the heartbeat continued following TTX application. Heartbeat frequency was lower in TTX-containing saline than in normal saline. These results show that, during juvenile development, the heart pacemaker is transferred from the heart muscle to the Cardiac Ganglion, which becomes the primary pacemaker and entrains the heart muscle activity to a higher frequency via EJPs.
Patsy S. Dickinson - One of the best experts on this subject based on the ideXlab platform.
-
Cloning of the first cDNA encoding a putative CCRFamide precursor: identification of the brain, eyestalk ganglia, and Cardiac Ganglion as sites of CCRFamide expression in the American lobster, Homarus americanus
Invertebrate Neuroscience, 2020Co-Authors: J. Joe Hull, Melissa A. Stefanek, Patsy S. Dickinson, Andrew E. ChristieAbstract:Over the past decade, many new peptide families have been identified via in silico analyses of genomic and transcriptomic datasets. While various molecular and biochemical methods have confirmed the existence of some of these new groups, others remain in silico discoveries of computationally assembled sequences only. An example of the latter are the CCRFamides, named for the predicted presence of two pairs of disulfide bonded cysteine residues and an amidated arginine-phenylalanine carboxyl-terminus in family members, which have been identified from annelid, molluscan, and arthropod genomes/transcriptomes, but for which no precursor protein-encoding cDNAs have been cloned. Using routine transcriptome mining methods, we identified four Homarus americanus (American lobster) CCRFamide transcripts that share high sequence identity across the predicted open reading frames but more limited conservation in their 5′ terminal ends, suggesting the Homarus gene undergoes alternative splicing. RT-PCR profiling using primers designed to amplify an internal fragment common to all of the transcripts revealed expression in the supraoesophageal Ganglion (brain), eyestalk ganglia, and Cardiac Ganglion. Variant specific profiling revealed a similar profile for variant 1, eyestalk ganglia specific expression of variant 2, and an absence of variant 3 expression in the cDNAs examined. The broad distribution of CCRFamide transcript expression in the H. americanus nervous system suggests a potential role as a locally released and/or circulating neuropeptide. This is the first report of the cloning of a CCRFamide-encoding cDNA from any species, and as such, provides the first non-in silico support for the existence of this invertebrate peptide family.
-
differential neuropeptide modulation of premotor and motor neurons in the lobster Cardiac Ganglion
Journal of Neurophysiology, 2020Co-Authors: Emily R Oleisky, Meredith E Stanhope, Andrew E. Christie, Joe J Hull, Patsy S. DickinsonAbstract:The American lobster, Homarus americanus, Cardiac neuromuscular system is controlled by the Cardiac Ganglion (CG), a central pattern generator consisting of four premotor and five motor neurons. Here, we show that the premotor and motor neurons can establish independent bursting patterns when decoupled by a physical ligature. We also show that mRNA encoding myosuppressin, a cardioactive neuropeptide, is produced within the CG. We thus asked whether myosuppressin modulates the decoupled premotor and motor neurons, and if so, how this modulation might underlie the role(s) that these neurons play in myosuppressin's effects on Ganglionic output. Although myosuppressin exerted dose-dependent effects on burst frequency and duration in both premotor and motor neurons in the intact CG, its effects on the ligatured Ganglion were more complex, with different effects and thresholds on the two types of neurons. These data suggest that the motor neurons are more important in determining the changes in frequency of the CG elicited by low concentrations of myosuppressin, whereas the premotor neurons have a greater impact on changes elicited in burst duration. A single putative myosuppressin receptor (MSR-I) was previously described from the Homarus nervous system. We identified four additional putative MSRs (MSR-II-V) and investigated their individual distributions in the CG premotor and motor neurons using RT-PCR. Transcripts for only three receptors (MSR-II-IV) were amplified from the CG. Potential differential distributions of the receptors were observed between the premotor and motor neurons; these differences may contribute to the distinct physiological responses of the two neuron types to myosuppressin.NEW & NOTEWORTHY Premotor and motor neurons of the Homarus americanus Cardiac Ganglion (CG) are normally electrically and chemically coupled, and generate rhythmic bursting that drives Cardiac contractions; we show that they can establish independent bursting patterns when physically decoupled by a ligature. The neuropeptide myosuppressin modulates different aspects of the bursting pattern in these neuron types to determine the overall modulation of the intact CG. Differential distribution of myosuppressin receptors may underlie the observed responses to myosuppressin.
-
In silico analyses suggest the Cardiac Ganglion of the lobster, Homarus americanus, contains a diverse array of putative innexin/innexin-like proteins, including both known and novel members of this protein family
Invertebrate Neuroscience, 2020Co-Authors: Andrew E. Christie, J. Joe Hull, Patsy S. DickinsonAbstract:Gap junctions are physical channels that connect adjacent cells, permitting the flow of small molecules/ions between the cytoplasms of the coupled units. Innexin/innexin-like proteins are responsible for the formation of invertebrate gap junctions. Within the nervous system, gap junctions often function as electrical synapses, providing a means for coordinating activity among electrically coupled neurons. While some gap junctions allow the bidirectional flow of small molecules/ions between coupled cells, others permit flow in one direction only or preferentially. The complement of innexins present in a gap junction determines its specific properties. Thus, understanding innexin diversity is key for understanding the full potential of electrical coupling in a species/system. The decapod crustacean Cardiac Ganglion (CG), which controls Cardiac muscle contractions, is a simple pattern-generating neural network with extensive electrical coupling among its circuit elements. In the lobster, Homarus americanus , prior work suggested that the adult neuronal innexin complement consists of six innexins (Homam-Inx1-4 and Homam-Inx6-7). Here, using a H. americanus CG-specific transcriptome, we explored innexin complement in this portion of the lobster nervous system. With the exception of Homam-Inx4, all of the previously described innexins appear to be expressed in the H. americanus CG. In addition, transcripts encoding seven novel putative innexins (Homam-Inx8-14) were identified, four (Homam-Inx8-11) having multiple splice variants, e.g., six for Homam-Inx8. Collectively, these data indicate that the innexin complement of the lobster nervous system in general, and the CG specifically, is likely significantly greater than previously reported, suggesting the possibility of expanded gap junction diversity and function in H. americanus .
-
molecular evidence for an intrinsic circadian pacemaker in the Cardiac Ganglion of the american lobster homarus americanus is diel cycling of heartbeat frequency controlled by a peripheral clock system
Marine Genomics, 2018Co-Authors: Andrew E. Christie, Patsy S. Dickinson, Micah G Pascual, Vittoria Roncalli, Matthew C Cieslak, Amanda N Warner, Tess J Lameyer, Meredith E Stanhope, Joe J HullAbstract:Abstract Whether Cardiac output in decapod crustaceans is under circadian control has long been debated, with mixed evidence for and against the hypothesis. Moreover, the locus of the clock system controlling Cardiac activity, if it is under circadian control, is unknown. However, a report that the crayfish heart in organ culture maintains a circadian oscillation in heartbeat frequency suggests the presence of a peripheral pacemaker within the Cardiac neuromuscular system itself. Because the decapod heart is neurogenic, with contractions controlled by the five motor and four premotor neurons that make up the Cardiac Ganglion (CG), a likely locus for a circadian clock is the CG itself. Here, a CG-specific transcriptome was generated for the lobster, Homarus americanus, and was used to assess the presence/absence of transcripts encoding putative clock-related proteins in the Ganglion. Using known Homarus brain/eyestalk ganglia clock-related proteins as queries, BLAST searches of the CG transcriptome were conducted for the five proteins that form the core clock, i.e., clock, cryptochrome 2, cycle, period and timeless, as well as for a variety of clock-associated, clock input pathway and clock output pathway proteins. With the exception of pigment dispersing hormone receptor [PDHR], a putative clock output pathway protein, one or more transcripts encoding each of the proteins searched for were identified from the CG assembly; no PDHR-encoding transcripts were found. RT-PCR confirmed the expression of all core clock transcripts in multiple independent CG cDNAs; RNA-Seq data suggest that both the motor and premotor neurons could contribute to the cellular locus of a pacemaker. These data provide support for the possible existence of an intrinsic circadian clock in the H. americanus CG, and form a foundation for guiding future anatomical, molecular and physiological investigations of circadian signaling in the lobster Cardiac neuromuscular system.
-
mechanisms underlying differential responses to the neuropeptide allatostatin c ast c in the Cardiac Ganglion of the lobster homarus americanus
The FASEB Journal, 2016Co-Authors: Meredith E Stanhope, David J. Schulz, Andrew E. Christie, Micah G Pascual, Tess J Lameyer, Devlin Shea, Megan Chi, Patsy S. DickinsonAbstract:In order to respond to environmental stimuli, animals need flexibility in the neural circuitry that controls behavioral patterns. Central pattern generators (CPGs), which control rhythmic behaviors...
Peter B. Sargent - One of the best experts on this subject based on the ideXlab platform.
-
effects of denervation on acetylcholine receptor clusters on frog Cardiac Ganglion neurons as revealed by quantitative laser scanning confocal microscopy
The Journal of Neuroscience, 1996Co-Authors: Hadley Wilson Horch, Peter B. SargentAbstract:We examined the effects of denervation on clusters of nicotinic acetylcholine receptors (AChRs) on autonomic neurons in the frog heart using immunofluorescence techniques and laser scanning confocal microscopy. We showed previously that normally innervated neurons have both large, brightly stained AChR clusters and small, dim AChR clusters. A majority (80%) of the large/bright AChR clusters are located at synaptic sites, whereas the small/dim clusters are distributed widely over the cell surface. Here, we use image analysis to identify these two classes of clusters on images generated from stacks of optical sections through neuronal cell bodies and to examine the effects of denervation on their number, size, and brightness (pixel intensity). Denervation reduces the number of large/ bright AChR clusters per cell to < 10% of sham-operated values and increases the number of small/dim clusters per cell by two- to threefold. These changes occur at 4 d of denervation, the earliest time examined, and are sustained for 6 weeks. The size of large/bright AChR clusters is decreased compared with sham-operated controls, and their brightness is unchanged. The size of small/dim AChR clusters is unchanged by denervation, but their brightness is increased. Denervation results in a shift in the contribution of each AChR cluster class to the total measurable AChR pool-from one dominated by large/bright clusters to one dominated by small/dim clusters. These results show that the nerve terminals on Cardiac Ganglion neurons appear to exert a continual and reversible influence on the organization of the postsynaptic membrane.
-
Synaptic and extrasynaptic distribution of two distinct populations of nicotinic acetylcholine receptor clusters in the frog Cardiac Ganglion
Journal of Neurocytology, 1996Co-Authors: Hadley L. Wilson Horch, Peter B. SargentAbstract:We examined the distribution of neuronal nicotinic acetylcholine receptor clusters in relation to synaptic sites on autonomic neurons in the frog heart using immunofluorescence techniques and laser scanning confocal microscopy. Acetylcholine receptor clusters were visualized using the rat anti- Electrophorus acetylcholine receptor monoclonal antibody no. 22 and cyanine 3.18-labelled goat anti-rat secondary antibody. Synaptic boutons were labelled with the mouse anti-synaptic vesicle protein SV2, monoclonal antibody no. 10h and cyanine 5.18-labelled goat anti-mouse secondary antibody. Acetylcholine receptor clusters on the neuronal surface exist in two populations that vary in size, staining intensity, and surface distribution. The more prominent population consists of large, brightly stained clusters numbering 30±15 per cell, while the second class is smaller and less brightly stained and numbers over 100 per cell. The large clusters tend to be organized into groups of 2–6 members. This arrangement results from the fact that 80% of the large clusters colocalize at synaptic boutons and that single boutons can have several associated clusters. The remaining 20% of large/bright acetylcholine receptor clusters are extrasynaptic, but they, too, are clustered and are found in close proximity to synaptic boutons. The small/dim acetylcholine receptor clusters are randomly distributed over the cell surface. The large/bright synaptic acetylcholine receptor clusters presumably underlie fast excitatory synaptic transmission. The small/dim clusters and the large/bright extrasynaptic clusters may represent intermediates in the metabolism of large/bright synaptic clusters.
-
The role of acetylcholinesterase in denervation supersensitivity in the frog Cardiac Ganglion.
The Journal of physiology, 1992Co-Authors: Laura C. Streichert, Peter B. SargentAbstract:1. The sensitivity of normal and denervated Cardiac Ganglion cells to the cholinergic agonists acetylcholine and carbamylcholine (carbachol) were compared in the frog, Rana pipiens. Acetylcholine and carbachol bind to the same acetylcholine receptors, but, unlike acetylcholine, carbachol is resistant to hydrolysis by acetylcholinesterase. 2. Sensitivity was assessed by the peak depolarization elicited in response to a sustained pulse of ligand emitted from a pipette positioned 10 microns from the Ganglion cell surface. This technique allows the sensitivity of the entire cell to be recorded with a single measurement. 3. The acetylcholine sensitivity of normal Cardiac Ganglion cells was increased by inhibiting extracellular acetylcholinesterase with echothiophate. 4. Denervation increased the sensitivity of Cardiac Ganglion cells to acetylcholine but not to carbachol. 5. Following the inhibition of extracellular acetylcholinesterase with echothiophate, sensitivity to acetylcholine was similar in normal and in denervated Ganglion cells. 6. The increased sensitivity to acetylcholine of Cardiac Ganglion cells following denervation is caused by a reduction in the hydrolysis of the transmitter by acetylcholinesterase rather than by changes in the number and/or properties of acetylcholine receptors.
-
denervation does not alter the number of neuronal bungarotoxin binding sites on autonomic neurons in the frog Cardiac Ganglion
The Journal of Neuroscience, 1991Co-Authors: Peter B. Sargent, Laura C. Streichert, G K Bryan, E N GarrettAbstract:The binding of neuronal bungarotoxin (n-BuTX; also known as bungarotoxin 3.1, kappa-bungarotoxin, and toxin F) was analyzed in normal and denervated parasympathetic Cardiac ganglia of the frog Rana pipiens, n-BuTX blocks both EPSPs and ACh potentials at 5-20 nM, as determined by intracellular recording techniques. Scatchard analysis on homogenates indicates that Cardiac ganglia have two classes of binding sites for 125I-n-BuTX: a high-affinity site with an apparent dissociation constant (Kd,app) of 1.7 nM and a Bmax (number of binding sites) of 3.8 fmol/Ganglion and a low-affinity site with a Kd,app of 12 microM and a Bmax of 14 pmol/Ganglion. alpha-Bungarotoxin does not appear to interfere with the binding of 125I-n-BuTX to either site. The high-affinity binding site is likely to be the functional nicotinic ACh receptor (AChR), given the similarity between its affinity for 125I-n- BuTX and the concentration of n-BuTX required to block AChR function. Light microscopic autoradiographic analysis of 125I-n-BuTX binding to the Ganglion cell surface reveals that toxin binding is concentrated at synaptic sites, which were identified using a synaptic vesicle-specific antibody. Scatchard analysis of autoradiographic data reveals that 125I- n-BuTX binding to the neuronal surface is saturable and has a Kd,app similar to that of the high-affinity binding site characterized in homogenates. Surface binding of 125I-n-BuTX is blocked by nicotine, carbachol, and d-tubocurarine (IC50 less than 20 microM), but not by atropine (IC50 greater than 10 mM). Denervation of the heart increases the ACh sensitivity of Cardiac Ganglion cells but has no effect upon the number of high-affinity binding sites for 125I-n-BuTX in tissue homogenates. Moreover, autoradiographic analysis indicates that denervation does not alter the number of 125I-n-BuTX binding sites on the Ganglion cell surface. n-BuTX is as effective in reducing Ganglion cell responses to ACh in denervated ganglia as it is in normally innervated ganglia. These results suggest that denervation alters neither the total number of nicotinic AChRs in the Cardiac Ganglion nor the number found on the surface of Ganglion cells. These autonomic neurons thus respond differently to denervation than do skeletal myofibers. The increase in ACh sensitivity displayed by Cardiac Ganglion cells upon denervation cannot be explained by changes in AChR number.
David J. Schulz - One of the best experts on this subject based on the ideXlab platform.
-
crustacean Cardiac Ganglion model reveals constraints on morphology and conductances
bioRxiv, 2021Co-Authors: Daniel S Dopp, David J. Schulz, Pranit Samarth, Jing S Wang, Daniel R Kick, Satish S. NairAbstract:The crustacean Cardiac Ganglion (CG) network coordinates the rhythmic contractions of the heart muscle to control the circulation of blood. The network consists of 9 cells, 5 large motor cells (LC1-5) and 4 small endogenous pacemaker cells (SCs). We report a new three-compartmental biophysical model of an LC that is morphologically realistic and includes provision for inputs from the SCs via a gap-junction coupled spike-initiation-zone (SIZ) compartments. To determine physiologically viable LC models in this realistic configuration, maximal conductances in three compartments of an LC are determined by random sampling from a biologically-characterized 9D-parameter space, followed by a three stage rejection protocol that checks for conformity with electrophysiological features from single cell traces. LC models that pass the single cell rejection protocol are then incorporated into a network model which is then used in a final rejection protocol stage. Using disparate experimental data, the study provides hitherto unknown structure-function insights related to the crustacean Cardiac Ganglion large cell, including predictions about morphology including the role of its SIZ, and the differential roles of active conductances in the three compartments. Further, we extend analyses of emergent conductance relationships and correlations in model neurons relative to their biological counterparts, allowing us to make inferences both with respect to the biological system as well as the implications of the ability to detect such relationships in populations of model neurons going forward.
-
dopamine maintains network synchrony via direct modulation of gap junctions in the crustacean Cardiac Ganglion
eLife, 2018Co-Authors: Brian J Lane, Satish S. Nair, Daniel R Kick, David K Wilson, David J. SchulzAbstract:The Large Cell (LC) motor neurons of the crab Cardiac Ganglion have variable membrane conductance magnitudes even within the same individual, yet produce identical synchronized activity in the intact network. In a previous study we blocked a subset of K+ conductances across LCs, resulting in loss of synchronous activity (Lane et al., 2016). In this study, we hypothesized that this same variability of conductances makes LCs vulnerable to desynchronization during neuromodulation. We exposed the LCs to serotonin (5HT) and dopamine (DA) while recording simultaneously from multiple LCs. Both amines had distinct excitatory effects on LC output, but only 5HT caused desynchronized output. We further determined that DA rapidly increased gap junctional conductance. Co-application of both amines induced 5HT-like output, but waveforms remained synchronized. Furthermore, DA prevented desynchronization induced by the K+ channel blocker tetraethylammonium (TEA), suggesting that dopaminergic modulation of electrical coupling plays a protective role in maintaining network synchrony.
-
dopamine maintains network synchrony via direct modulation of gap junctions in the crustacean Cardiac Ganglion
bioRxiv, 2018Co-Authors: Brian J Lane, Satish S. Nair, Daniel R Kick, David K Wilson, David J. SchulzAbstract:The Large Cell (LC) motor neurons of the crab (C. borealis) Cardiac Ganglion have variable membrane conductance magnitudes even within the same individual, yet produce identical synchronized activity in the intact network. In a previous study (Lane et al. 2016) we blocked a subset of K+ conductances across LCs, resulting in loss of synchronous activity. In this study, we hypothesized that variability of conductances could make LCs vulnerable to desynchronization during neuromodulation. We exposed LCs to serotonin (5HT) and dopamine (DA) while recording simultaneously from multiple LCs. Both amines had distinct excitatory effects on LC output, but only 5HT caused desynchronized output. We further determined that DA rapidly increased gap junctional conductance. Co-application of both amines induced 5HT-like output, but waveforms remained synchronized. Furthermore, DA prevented desynchronization induced by the K+ channel blocker tetraethylammonium (TEA), suggesting that dopaminergic modulation of electrical coupling plays a protective role in maintaining network synchrony.
-
homeostatic plasticity of excitability in crustacean central pattern generator networks
Current Opinion in Neurobiology, 2017Co-Authors: David J. Schulz, Brian J LaneAbstract:Plasticity of excitability can come in two general forms: changes in excitability that alter neuronal output (e.g. long-term potentiation of intrinsic excitability) or excitability changes that stabilize neuronal output (homeostatic plasticity). Here we discuss the latter form of plasticity in the context of the crustacean stomatogastric nervous system, and a second central pattern generator circuit, the Cardiac Ganglion. We discuss this plasticity at three levels: rapid homeostatic changes in membrane conductance, longer-term effects of neuromodulation on excitability, and the impacts of activity-dependent feedback on steady-state channel mRNA levels. We then conclude with thoughts on the implications of plasticity of excitability for variability of conductance levels across populations of motor neurons.
-
mechanisms underlying differential responses to the neuropeptide allatostatin c ast c in the Cardiac Ganglion of the lobster homarus americanus
The FASEB Journal, 2016Co-Authors: Meredith E Stanhope, David J. Schulz, Andrew E. Christie, Micah G Pascual, Tess J Lameyer, Devlin Shea, Megan Chi, Patsy S. DickinsonAbstract:In order to respond to environmental stimuli, animals need flexibility in the neural circuitry that controls behavioral patterns. Central pattern generators (CPGs), which control rhythmic behaviors...
Rodney L Parsons - One of the best experts on this subject based on the ideXlab platform.
-
evidence for afferent fiber innervation of parasympathetic neurons of the guinea pig Cardiac Ganglion
Journal of The Autonomic Nervous System, 1995Co-Authors: Jean C Hardwick, Gary M Mawe, Rodney L ParsonsAbstract:Abstract The present study was done to establish whether peptidergic afferent inputs can modulate parasympathetic neurons of the guinea-pig Cardiac Ganglion. Whole mount preparations from the guinea-pig heart were utilized to localize afferent terminals by immunohistochemistry and for intracellular recordings from individual neurons in situ. Action potentials could be elicited by both intracellular current injection and stimulation of interGanglionic fiber bundles. Two types of neuron, phasic (95%) and tonic (5%) as defined by their firing properties, were observed. High frequency (5–10 Hz) interGanglionic fiber stimulation produced a calcium-dependent, slow depolarization in many cells which was not blocked by 100 μM hexamethonium or 1 μM atropine. A prolonged depolarization was also produced by local application of capsaicin (1 mM), which releases substance P and CGRP from afferent nerve terminals. Microejection of the mammalian tachykinins substance P, neurokinin A and neurokinin B (all at 100 μM), also produced a slow depolarization. Application of specific agonists for the tachykinin receptor subtypes indicated that these neurones express both NK2 and NK3 receptors. Individual cells were filled with neurobiotin to examine their morphology and the preparations were counter-stained for SP-like immunoreactivity. The results demonstrated that SP-positive fibers are found in close apposition to both phasic and tonic neurons. From these results, we suggest that the parasympathetic neurons of the guinea-pig Cardiac Ganglion receive inputs from peptidergic, afferent fibers and that this input provides a pathway for potential local reflex control of Cardiac function.
-
evidence for afferent fiber innervation of parasympathetic neurons of the guinea pig Cardiac Ganglion
Journal of The Autonomic Nervous System, 1995Co-Authors: Jean C Hardwick, Gary M Mawe, Rodney L ParsonsAbstract:The present study was done to establish whether peptidergic afferent inputs can modulate parasympathetic neurons of the guinea-pig Cardiac Ganglion. Whole mount preparations from the guinea-pig heart were utilized to localize afferent terminals by immunohistochemistry and for intracellular recordings from individual neurons in situ. Action potentials could be elicited by both intracellular current injection and stimulation of interGanglionic fiber bundles. Two types of neuron, phasic (95%) and tonic (5%) as defined by their firing properties, were observed. High frequency (5-10 Hz) interGanglionic fiber stimulation produced a calcium-dependent, slow depolarization in many cells which was not blocked by 100 microM hexamethonium or 1 microM atropine. A prolonged depolarization was also produced by local application of capsaicin (1 mM), which releases substance P and CGRP from afferent nerve terminals. Microinjection of the mammalian tachykinins substance P, neurokinin A and neurokinin B (all at 100 microM), also produced a slow depolarization. Application of specific agonists for the tachykinin receptor subtypes indicated that these neurons express both NK2 and NK3 receptors. Individual cells were filled with neurobiotin to examine their morphology and the preparations were counter-stained for SP-like immunoreactivity. The results demonstrated that SP-positive fibers are found in close apposition to both phasic and tonic neurons. From these results, we suggest that the parasympathetic neurons of the guinea-pig Cardiac Ganglion receive inputs from peptidergic, afferent fibers and that this input provides a pathway for potential local reflex control of Cardiac function.
-
biogenic amine localization in Cardiac Ganglion intrinsic neurons electron microscopic histochemistry of sif cells
Brain Research Bulletin, 1991Co-Authors: Richard M Kriebel, Allen Angel, Rodney L ParsonsAbstract:Abstract The parasympathetic Cardiac Ganglion in the mudpuppy, N. maculosus , contains postGanglionic nerve cells and intrinsic neurons, many of which are small intensely fluorescent (SIF) cells. Several bioactive substances have been localized in the intrinsic nerve cells which may have integrative effects at synapses within the Ganglion. Ganglionic intrinsic neurons can be identified electron microscopically by the presence of numerous cytoplasmic granular vesicles 80–120 nm in diameter. Throughout the Ganglion there are bundles of unmyelinated fibers some of which are filled with granular and agranular vesicles and axosomatic terminals with similar vesicles synapsing on principal parasympathetic nerve cells. To understand the aminergic contribution to Ganglionic synaptic circuitry the chromaffin reaction was used. The intrinsic neurons (i.e., SIF cells) were readily identified by their characteristic intracellular granule population. All intrinsic nerve cells identified showed granules which were positively labelled by the chromaffin reaction. Granular vesicles in synaptic profiles on principal cells (P cells) were also labelled indicating a direct aminergic synaptic innervation to these cells. The cell bodies of intrinsic neurons, ensheathed with supportive glial-like cellular processes, rarely received synapses. Elemental microanalysis was used to verify the chromium content of the electron dense product within the granular vesicles. These studies demonstrated direct aminergic synaptic input to at least a subpopulation of principal parasympathetic cells in the Cardiac Ganglion of mudpuppy.