Lobster Cardiac Ganglion Research Articles

Integrative Neurophysiology of the Lobster Cardiac Ganglion

The synchronized bursts of impulses produced by the nine neurons of the isolated Homarus cardiac ganglion are usually initiated by Cell 7. Activity in all other cells commences with very short latency thereafter. Impulses in most cells originate in trigger zones located 1–2 mm from the cell body, but the first several impulses in Cells 8 and 9 frequently originate in distal trigger zones some distance from the somata. Large cells fire at a high initial frequency, dropping rapidly to a low frequency plateau. Small cells exhibit a more tonic behavior and fire at intermediate rates. More anterior small cells tend to fire faster than more posterior ones. The major synaptic interactions are the impulse-mediated excitatory ones from small cells to large cells, and possibly to more anterior small cells. There are weak interactions from large cells back onto small cells, and very specific interactions from Cells 1 and 2 onto 3A, 4A, 5A, and 3B 4B 5B respectively. The large discrete EPSPs generated in large cells by small cell impulses appear to be the explanation for “discrete positioning” in large-cell firing patterns. In this situation, large-cell impulses only fire at discrete times during the burst, regardless of the actual large-cell pattern. The overall view is of a two-layered neural system in which the small cells possess an endogenous oscillatory driver potential, synchronized by synaptic and electrotonic interactions, and driving a train of impulses in each cell. This activates excitatory synapses on the large cells, which combined with a triggered driver potential in each large cell, produces synchronized trains of motor impulses which activate the heart muscle, causing the heartbeat.

The analysis of nonlinear synaptic transmission.

In order to characterize synaptic transmission at a unitary facilitating synapse in the lobster cardiac ganglion, a new nonlinear systems analysis technique for discrete-input systems was developed and applied. From the output of the postsynaptic cell in response to randomly occurring presynaptic nerve impulses, a set of kernels, analogous to Wiener kernels, was computed. The kernels up to third order served to characterize, with reasonable accuracy, the input-output properties of the synapse. A mathematical model of the synapse was also tested with a random impulse train and model predictions were compared with experimental synaptic output. Although the model proved to be even more accurate overall than the kernel characterization, there were slight but consistent errors in the model's performance. These were also reflected as differences between model and experimental kernels. It is concluded that a random train analysis provides a comprehensive and objective comparison between model and experiment and automatically provides an arbitrarily accurate characterization of a system's input-output behavior, even in complicated cases where other approaches are impractical.

Intracellular potentials in the small cells and cellular interaction in the cardiac ganglion of the lobster Panulirus Japonicus

Abstract o 1. The electrical activity in the lobster cardiac ganglion was studied by means of intracellular microelectrodes, attention being focused on membrane potential changes in the small cells. 2. In many cases the small cell produced a periodic burst of spikes superimposed on a slow potential. 3. The synaptical interaction was observed among the small cells. 4. Most of the small cells innervated the large cells. 5. Intracellular stimulation of the small cell was effective in inducing the burst of discharges in the ganglion.

Synaptic interactions in the cardiac ganglion of the spiny lobsterPanulirus interruptus

Synaptic interactions between neurons of the spiny lobster (Panulirus interruptus) cardiac ganglion have been investigated. All four small cells make synaptic contacts with all large cells (Fig. 1). The anterior four large cells all respond with similar synaptic depolarizations in response to a small cell impulse as follows: to cell 6–16.4 mV; to cell 7-3.1 mV; to cell 8-1.9 mV; and to cell 9-1.3 mV (Fig. 2). The average synaptic potentials measured in the soma of cell 5 are smaller: to cell 6-2.5 mV; to cell 7-1.5 mV; to cell 8-1.0 mV; and to cell 9-0.7 mV. Cell 1-4 PSP's due to cell 6 impulses antifacilitate strongly, while those from cells 7, 8 and 9 antifacilitate only weakly if at all. PSP's in cell 5 show neither facilitation nor antifacilitation. Cell 6 receives spike mediated input from some small cells (Fig. 7). Synaptic connections between cells 8 and 9 if they exist at all, are very weak (Fig. 6). The most important interactions between cells 8 and 9 are probably via electrotonic connections.

Antifacilitation and facilitation in the cardiac ganglion of the spiny lobsterPanulirus interruptus

Antifacilitation and facilitation of synaptic transmission between cell 6 and the large cells were studied in the spiny lobster cardiac ganglion. Two-impulse experiments invariably produced antifacilitation in the second large-cell PSP at all inter-pulse intervals (10 msec to 10 sec) (Fig. 2). When conditioning trains with 2–4 impulses preceded the test impulse, the test PSP was antifacilitated at intervals of less than 100 msec and usually facilitated at intervals greater than 100 msec (Fig. 3). At intervals shorter than 50 msec the test PSP amplitude was nearly independent of the number of conditioning impulses. At greater intervals, the test PSP amplitude was a linear function of the number of impulses in the conditioning train (Fig. 4 and 5). A model was constructed based on the assumption thatF (defined asVT/V0, whereV0 andVT are the control and test PSP amplitudes, respectively) is the sum of antifacilitation (F−) and facilitation (F+) (Fig. 9).F− depends only on the separation between the last conditioning impulse and the test impulse and is described by the equation:\(F^ - = 1.0 - A_1 e^{{{ - t} \mathord{\left/ {\vphantom {{ - t} {\tau _1 }}} \right. \kern-\nulldelimiterspace} {\tau _1 }}} - A_2 e^{{{ - t} \mathord{\left/ {\vphantom {{ - t} {\tau _2 }}} \right. \kern-\nulldelimiterspace} {\tau _2 }}} \), wheret is the conditioning-to-test interval in seconds,A1=0.26,A2=0.74,τ1=0.02 sec, andτ2=4.1 sec.F+ is described by the equationN C\((1 - e^{{{ - t} \mathord{\left/ {\vphantom {{ - t} {\tau _4 }}} \right. \kern-\nulldelimiterspace} {\tau _4 }}} )^2 \cdot e^{{{ - t} \mathord{\left/ {\vphantom {{ - t} {\tau _3 }}} \right. \kern-\nulldelimiterspace} {\tau _3 }}} \), whereN is the number of conditioning impulses,t is the interval between the end of the conditioning train and the test impulses,τ3=3.6 sec,τ4=0.08 sec, andC is a constant.

Functional Organization of the Cardiac Ganglion of the Lobster, Homarus americanus

External recording and stimulation, techniques were used to determine which neurons and interactions are essential for production of the periodic burst discharge in the lobster cardiac ganglion. Burst activity can be modulated by brief single shocks applied to the four small cells, but not by similar stimulation of the five large cells, suggesting that normally one or more small cells primarily determine burst rate and duration. Repetitive electrical stimulation of large cells initiates spike activity in small cells, probably via excitatory synaptic and/or electrotonic connections which may normally act to prolong bursts and decrease burst rate. Transection of the ganglion can result in burst activity in small cells in the partial or complete absence of large cell spike activity, but large cells isolated from small cell excitatory synaptic input by transection or by application of dinitrophenol do not burst. Generally, transections which decrease excitatory feedback to small cells are accompanied by an increase in burst rate, but mean spike frequency over an entire burst cycle stabilizes at the original level within 10-30 min for various groups of cells whose spike-initiating sites are still intact. These and previous results suggest that the system is two layered: one or more small cells generate the burst pattern and impose it on the large cells which are the system's motorneurons.

Impulse Activity and Pattern of Large and Small Neurones in the Cardiac Ganglion of the Lobster, Panulirus Japonicus

ABSTRACT The cardiac ganglion of the lobster, which contains five large and four small cells (Alexandrowicz, 1932), produces integrated patterns of burst discharges. Maynard (1955, 1966) described how this ganglion may be compared to a miniature central nervous system, and pointed out that integrative processes occurring within the ganglion are of great interest because analyses of a simple nervous system may be an approach to the study of integration in complex nervous systems. Electrophysiological investigations of these ganglion cells have been reviewed by Hagiwara (1961). Intracellular studies have been made in detail on large cells of Panulirus (Hagiwara & Bullock, 1957; Bullock & Terzuolo, 1957; Watanabe, 1958; Otani & Bullock, 1959; Hagiwara, Watanabe & Saito, 1959; Watanabe & Bullock, 1960; Tazaki, 1971b, 1972a). The conclusion concerning their activity is as follows: large cells (followers) are innervated by common presynaptic nerve fibres from small cells (pacemakers), and potential changes during the burst are several kinds of synaptic potentials and spikes. This conclusion is not, however, valid for the Homarus ganglion. Cooke (1966) and Connor (1969) have studied the intracellular activity of its large cells. Connor (1969) has concluded that potential deflexions are due toendogenous activity of the respective neurones and not to synaptic potentials.

Electrical interaction among large cells in the cardiac ganglion of the lobster, Panulirus japonicus.

AbstractTo investigate electrical interaction among large cells in the lobster cardiac ganglion, electrotonic transmission between the somata of two such cells was observed by applying current pulses of two different durations and recording induced responses in the membrane potential of soma. The brief potential changes induced in one soma were transmitted to an adjacent soma through electrotonic pathways in the same way as the longer potential changes. However attenuation was greater for the shorter pulses. The amplitude of the soma spike markedly decreased compared to that of the axon spike, and the ratio was about 5.5. The soma spike was not a regenerative response of the soma membrane, but it was an electrotonic spread of the axon spike. The attenuation ratio of the soma spike was almost the same as that measured for a brief potential change such as a spike applied to the soma. These findings indicate that the soma spike spreads electrotonically to the adjacent soma through the electrical connections, while the axon spike does not. Such electrical transmission of the spike was extremely weak. The slow potential, electronic transmission of which had been observed between large cells, was restricted to the soma. The results suggest that the electrotonic pathways interconnect the somata of large cells in the anterior part of the ganglionic trunk, but not the axons. Electrical transmission of the spike through the pathways is very weak because of the inexcitable membrane of the somata. The electrotonic pathways are considered to be fibre‐like connections between dendrites arising from the somata.

Evidence for an electrogenic sodium pump in follower cells of the lobster cardiac ganglion.

Evidence for an electrogenic sodium pump in follower cells of the lobster cardiac ganglion.D R Livengood, and K KusanoD R Livengood, and K KusanoPublished Online:01 Mar 1972https://doi.org/10.1152/jn.1972.35.2.170MoreSectionsPDF (3 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByReliable, Responsive Pacemaking and Pattern Generation With Minimal Cell Numbers: the Crustacean Cardiac GanglionThe Biological Bulletin, Vol. 202, No. 2The effect of subtype-selective muscarinic receptor antagonists on the cholinergic current in motoneurons of the lobster cardiac ganglionBrain Research, Vol. 552, No. 1Proctolin activates a slow, voltage-dependent sodium current in motoneurons of the lobster cardiac ganglionNeuroscience Letters, Vol. 106, No. 1-2Studies on the crustacean cardiac ganglionComparative Biochemistry and Physiology Part C: Comparative Pharmacology, Vol. 91, No. 1Electrogenic sodium pumping in Mytilus smooth muscleComparative Biochemistry and Physiology Part A: Physiology, Vol. 66, No. 2The effect of caffeine on the neurons of a mammalian sympathetic ganglionNeuroscience, Vol. 3, No. 8 More from this issue > Volume 35Issue 2March 1972Pages 170-86 https://doi.org/10.1152/jn.1972.35.2.170PubMed5028657History Published online 1 March 1972 Published in print 1 March 1972 Metrics

Changes in the electrical activity of the lobster cardiac ganglion caused by local application of high calcium or high potassium solutions.

Electrical activity of lobster cardiac ganglion was studied by intracellular recording when the trunk had been partially treated with high Ca or high K solution. Special attention was paid to the functional relation between ganglion cells. Activity of the posterior half of the ganglion trunk was mainly represented by that of the fifth large cell.1. When the Ca was applied to the four large cells in the anterior part of the trunk, their activity was depressed completely, but often slow potentials and trains of synaptic potentials induced by intact cells remained.2. When the Ca bathed the posterior half of the trunk, the activity of anterior four large cells was sometimes depressed completely, or some components of the burst remined.3. When the K was applied to the anterior part of the trunk, periodic burst was still observable in the group of anterior four large cells and hardly had a relation to impinging synaptic potentials.4. Periodic burst was found as before in the four large cells with frequent occurrence of trains of small synaptic potentials even after the K was applied to the posterior part of the trunk.5. In preparations producing periodic burst in the group of large cells, the burst activity was sometimes depressed completely or inhibited remarkably when the Ca was applied to either half of the trunk. On the contrary, interval and duration of the burst were shortened when the K was applied to either half of the preparation.6. Ca solution produced an inhibitory effect on the intact cells as the result of electrotonic spread of hyperpolarization manifested in the applied half of the trunk.

Small synaptic potentials in burst activity of large neurons in the lobster cardiac ganglion.

Some characteristics of synaptic potentials arising in the large cells of the lobster cardiac ganglion were investigated by means of intracellular recording and current injection.1. The spontaneous burst was mainly composed of two kinds of synaptic potentials differing in various features, indicating that the large cells were innervated by two common presynaptic nerve fibers from pacemakers.2. Antifacilitation was observed in large synaptic potentials, while it was not observed in small synaptic potentials.3. Depolarization of the large cell accelerated the initiation of large synaptic potentials, andhyperpolarization impeded it. The electrotonic interaction between large cells and the presynaptic nerve cells, which produce large synaptic potentials, was rather strong.4. Polarization of the large cell had less effect on the initiation of small synaptic potentials than on that of large synapticpotentials; the electrotonic interaction between large cells and the presynaptic nerve cells, which produce small synaptic potentials, was exceedingly weak.5. A brief current pulse applied to the large cell evoked the slow potential, which was separated from a train of small synaptic potentials. The positive feedback of the slow potential was demonstrated well.6. Repetitive small synaptic potentials had an acceleratory effect on the burst initiation. The rate of slow depolarization increased with development of small synaptic potentials.7. Two types of presynaptic nerve cells exhibited differences in time courses of repetitive discharges; one produced a brief train of discharges, and the other an extensive train.8. It was concluded that the large cells are controlled by two types of presynaptic nervecells; one evokes large synaptic potentials, initiating impulses, and the other induces small synaptic potentials, increasing excitability of the postsynaptic membrane. The latter controls the former. The large cell behaves as a pacemaker when presynaptic nerve cells become inactive or when their activities are delayed.

The electrophysiology of muscle fibers in the hearts of Decapod Crustaceans

AbstractIntracellular recordings from the muscle fibers in contracting hearts of the crayfish and the lobster show a sequence of potential changes superficially resembling the vertebrate cardiac action potential. In the Crustaceans, however, the plateau part of the depolarization is produced by fused junctional potentials, elicited by the firing of motor neurons whose cell bodies lie in the cardiac ganglion. The first or second JP elicits an active membrane response that probably is produced by Ca2+ influx, since it is blocked by Mn2+. Local currents can flow between the individual muscle fibers, presumably by way of gap junctions. Simultaneous records were made extracellularly from one of the efferent nerves coming from the lobster cardiac ganglion and intracellularly from a muscle fiber. Four motor axons were identified in the efferent nerve and the firing of each of these sets up a JP at each point on the muscle membrane. A fifth motor neuron may also run to each muscle fiber. In the isolated heart the motor outflow from the cardiac ganglion is quite variable. Nevertheless, the system is such that the potential changes on the muscle membrane are almost indistinguishable from beat to beat. The hermit crab cardiac muscle usually has only two JPs per beat; the first JP sets up an overshooting spike.

Modulation of activity of one neuron by subthreshold slow potentials in another in lobster cardiac ganglion.

A direct demonstration is given of interaction between specific neurons without impulses, via graded slow potentials electrotonically spread from one cell to another. Repetitive polarizing or depolarizing current pulses of 50 to 200 msec. and subthreshold intensity were passed through an intracellular electrode in the soma of a follower cell of the isolated ganglion. When the frequency is near the natural rhythm of impulse bursts corresponding to heart beats and arising in a pacemaker cell 5 to 10 mm. posteriorly, the bursts rapidly become synchronized with the pulses. The effect disappears upon withdrawing the intracellular electrode. Brief pulses or full spikes in the follower are not effective. Hyperpolarizing long pulses attract the burst to a fixed period after the end of the pulse, depolarizations after the beginning of the pulse. The natural rhythm promptly reappears when the pulses are stopped and occasionally breaks through during weak repetitive pulses. Current pulses in postsynaptic cells also alter the threshold of a presynaptic neuron to externally applied stimuli. Some kind of direct, low resistance pathway for electrotonic spread, discriminating against spikes because of their brevity, is inferred, providing a basis for subthreshold interaction which is specific and not by way of a field effect. Due to the sensitivity of modulation of ongoing rhythms, electrotonic currents can be effective even after decrementing over several millimeters.

THE INTERACTION OF ELECTRICAL ACTIVITY AMONG NEURONS OF LOBSTER CARDIAC GANGLION

1. The potential changes were recorded from the individual large cells of the lobster cardiac ganglion with the aid of intra-cellular microelectrodes. Special attention was paid to the interaction among the cells, and, using a dual beam oscilloscope, simultaneous recording was made from two different cells.2. The “follower” type of potential was the most common and similar to that obtained in ganglion cells of an American lobster, described by Hagiwara and Bullock (10), and Bullock and Terzuolo (7).3. The synaptic potentials in two adjacent cells were closely synchronized. This seems to indicate existence of common presynaptic fibers. On the other hand the superimposed spikes were not always synchronized.4. With an inward current applied to the cell membrane, the spike generation was often blocked. On the other hand, however, the synaptic potentials were increased in amplitude.5. An outward current applied to the cell membrane caused a depolarization. With sufficient strength a spike or a series of spikes was produced superimposed on the depolarization.6. Electrotonic potentials were elicited by an applied current, not only in the cell in which the current electrode was inserted, but also in a neighboring cell in which no current electrode was inserted, with a reduced amplitude and a delayed time course. This phenomenon was regarded as existence of “electrical connections” among large cells.7. In some specimens when the small cells were anaesthetized with 0.1% procain-sea water, a slow oscillatory potential change was produced in one of the large cells, which has variable amplitude of up to 10 mV and frequency of about one per second, and was superimposed with a spike or a series of spikes. 8. The slow oscillatory potentials appeared in a neighboring cell with a certain phase shift and a reduced amplitude. This phenomenon was explained as a sort of electrotonic spread which is made possible by the electrical connection among cells.

Intracellular potentials in pacemaker and integrative neurons of the lobster cardiac ganglion.

Intracellular potentials in pacemaker and integrative neurons of the lobster cardiac ganglion.