Electrical properties of the pacemaker neurons in the heart ganglion of a stomatopod, Squilla oratoria.
01 Mar 1967-The Journal of General Physiology (The Rockefeller University Press)-Vol. 50, Iss: 4, pp 813-838
TL;DR: Comparison with action potentials caused by axonal stimulation and analysis of time relations indicate that with stronger currents the soma membrane is directly stimulated whereas with weaker currents the impulse first arises in the axon and then invades the Soma.
Abstract: In the Squilla heart ganglion, the pacemaker is located in the rostral group of cells. After spontaneous firing ceased, the electrophysiological properties of these cells were examined with intracellular electrodes. Cells respond to electrical stimuli with all-or-none action potentials. Direct stimulation by strong currents decreases the size of action potentials. Comparison with action potentials caused by axonal stimulation and analysis of time relations indicate that with stronger currents the soma membrane is directly stimulated whereas with weaker currents the impulse first arises in the axon and then invades the soma. Spikes evoked in a neuron spread into all other neurons. Adjacent cells are interconnected by electrotonic connections. Histologically axons are tied with the side-junction. B spikes of adjacent cells are blocked simultaneously by hyperpolarization or by repetitive stimulation. Experiments show that under such circumstances the B spike is not directly elicited from the A spike but is evoked by invasion of an impulse or electrotonic potential from adjacent cells. On rostral stimulation a small prepotential precedes the main spike. It is interpreted as an action potential from dendrites.
Citations
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TL;DR: Visceral nerve stimulation at increasing intensities produced graded antidromic spikes from, at least, 12 axon branches from the Br bursting neuron of Helix pomatia, which might be the basis of the slight and slow modulation exerted by Br upon Br', which resulted in phase relationship between the two bursters.
12Â citations
TL;DR: 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.
Abstract: To 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.
11Â citations
TL;DR: The effect of medullary stimulation on breathing movement was studied in the adult lamprey, Entosphenus japonicus, and an analogy between respiratory rhythmogenesis in the lamprey and cardiac pacemaking in crustacean heart ganglion was considered.
Abstract: 1. The effect of medullary stimulation on breathing movement was studied in the adult lamprey, Entosphenus japonicus. 2. A single, as well as low frequency (less than 5 Hz) pulses applied extracellularly to the medial part of the medulla (as shown in Fig. 1) produced one-to-one movement (contraction followed by relaxation) of branchial baskets, which are similar in shape, as well as in bilateral synchronization, to spontaneously occurring movement. 3. medullary stimulation never produced active immediate relaxation of branchial baskets. Intravenous application of d-tubocurarine resulted in sustained relaxation of branchial baskets. EMG recorded from branchial muscles always correlated with the phase of contraction of branchial baskets. 4. The rhythm of respiratory movement was reset by driving stimuli at low frequencies. Alteration of driving frequency did not markedly affect the duration of branchial movement. 5. With high frequency stimulation (more than 5 Hz), individual responses fused into one continuous contraction (sustained compression) of branchial baskets; it may be called a systolic arrest or expiratory arrest of breathing movement. 6. After the repetitive stimulation had been turned off, there was a pause in the respiratory movement. This sustained relaxation of branchial baskets may be called a diastolic arrest or inspiratory arrest. During this arrest, applied pulse shocks induced one-to-one movement of branchial baskets. 7. These results were discussed whilst considering an analogy between respiratory rhythmogenesis in the lamprey and cardiac pacemaking in crustacean heart ganglion.
8Â citations
01 Jan 2002
TL;DR: The CG is demonstrated to be an accessible and robust in vitro preparation that demonstrates that individual neurons are endowed with an intrinsic burst-organizing mechanism that insures a patterned output to any appropriate excitatory drive and that interconnections among a small number of neurons with such a capability can ensure coordinated, patterned, rhythmic highly fault-tolerant output from the ensemble.
Abstract: The crustacean cardiac ganglion (CG) is composed of 6-16 neurons, 9 in most decapods, that autonomously provide rhythmically recurring barrages of action potentials to activate the heart muscle. In Malacostraca, the heart is neurogenic and in adults dependent for its beating on the impulses from the ganglion. The CG, consisting of the neurons and their processes, wrapped in glial and connective tissue, forms an elongated, discrete branching trunk in or on the heart. It can be dissected from the heart and will continue to show spontaneous, rhythmical bursting. As an accessible and robust in vitro preparation, the CG joins a list of crustacean preparations that have provided insights into fundamental neurophysiological mechanisms, in this case the mechanisms by which small neuronal networks can generate rhythmical, patterned output (review: Wiens 1982). Possibly the most important insight arises from the demonstration that individual neurons are endowed with an intrinsic burst-organizing mechanism that insures a patterned output to any appropriate excitatory drive and that interconnections among a small number of neurons with such a capability can ensure coordinated, patterned, rhythmic highly fault-tolerant output from the ensemble. Patterned or bursting impulses are, of course, the essential effective activator of responses of other neurons or muscles or secretory cells. The contribution of intrinsic neuronal properties in pattern generation has become more widely recognized, not only in other crustacean ganglia (e.g. plateau potentials of the stomatogastric ganglion, Russell and Hartline 1978, 1982, 1984; Dickinson and Nagy 1983; Harris-Warrick et al. 1992a), but as a proven or suspected feature of pattern generation in neurons and neuroendocrine cells (Cooke and Stuenkel 1985) of most if not all animal groups (e.g. insects, Hancox and Pitman 1991; molluscs, Kramer and Zucker 1985; Hurwitz and Susswein 1996; Perrins and Weiss 1998; annelids, Arbas and Calabrese 1987; vertebrates, Llinas and Sugimori, 1980, Purkinje cells; Deschenes et al. 1982; Llinas and Jahnsen 1982, thalamic neurons; Legendre et al. 1982, hypothalamic neurons; Hounsgaard and Kiehn 1989, review Hultborn 1999, motorneurons; Grillner et al. 1991, lamprey swimming; Rekling and Feldman 1998, respiratory rhythm
6Â citations
TL;DR: The results suggest that the heart of V. hilgendorfii is neurogenic, with a single cardiac neuron having both pacemaker and motor functions.
Abstract: We examined morphologically innervation of the heart of the ostracod crustacean Vargula hilgendorfii. The heart is single chambered and composed of a single layer of myocardial cells characterized by localization of myofibrils at the epicardial side. A nerve net in the heart was determined by vital staining with methylene blue. Electron microscopy revealed that a single neuron situated on the outer surface of the dorsal heart wall sends an axon into the heart wall. The axon of the dorsal neuron is branched widely and forms many neuromuscular junctions on the myocardial cells. A pair of extrinsic nerves, each of which contains several axons, enters the heart bilaterally and forms numerous nerve terminals on the dorsal neuron and myocardial cells, while no synaptic structures were found in the nerve terminals. The results suggest that the heart of V. hilgendorfii is neurogenic, with a single cardiac neuron having both pacemaker and motor functions.
5Â citations
Cites background from "Electrical properties of the pacema..."
...In stomatopods, the cardiac ganglion is composed of 15 motor neurons (Alexandrowictz, 1934) with several anterior neurons giving the pacemaker function (Watanabe et al., 1967)....
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...In stomatopods, the cardiac ganglion is composed of 15 motor neurons (Alexandrowictz, 1934) with several anterior neurons giving the pacemaker function (Watanabe et al., 1967)....
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References
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512Â citations
369Â citations
TL;DR: The results reported here were obtained with a method of direct stimulation of single spinal motoneurons of Japanese toads using the same microelectrode with certain compensation circuits for both stimulation and recording.
Abstract: THE ACTIVITIES of single nerve cells explored with intracellular electrodes have been reported by several authors (1, 3, 4, 14). In those reports researches whether were made in connection with orthodromic or antidromic. It the excitation via neural is desirable, however, to pathways, adopt the method of direct stimulation in order to get more detailed knowledge concerning the physiological properties of the soma membrane. Since the insertion out ordinarily without of microelectrodes into the visual control, there is no neurons must be carried possibility of having two separate microelectrodes lodging in the same neuron, the one for stimulation and the other for recording. The use of a twin-microelectrode was also found inappropriate for the present purpose, because of the electrical interference between each electrode due to their capacitative coupling. The only method available was therefore to use the same microelectrode with certain compensation circuits for both stimulation and recording. The results reported here were obtained with such a method on single spinal motoneurons of Japanese toads.
332Â citations
"Electrical properties of the pacema..." refers background in this paper
...In the motoneurons of toads and cats, direct stimulation produced a spike in the initial segment before the soma-dendritic membrane was excited (Araki and Otani, 1955; Frank and Fuortes, 1956; Coombs, Curtis, and Eccles, 1957)....
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...This property is observed in many other nerve cells, for example, the toad or cat motoneurons (Araki and Otani, 1955; Coombs, Curtis, and Eccles, 1957), the stretch receptor cell of a lobster (Edwards and Ottoson, 1958), although there are some exceptional neurons, for example, the supramedullary cells of the puffer (Bennett, Crain, and Grundfest, 1959)....
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317Â citations
TL;DR: Curves of the strength of the stimuli required for eliciting small or full spikes have been constructed in a number of conditions and it is assumed that threshold of the major portions of the soma membrane is higher than the threshold ofThe axon, the transition occurring over a finite area near the axon hillock.
Abstract: 1. Spikes evoked in spinal motoneurons by antidromic stimulation normally present an inflection in their rising phase. A similar inflection is present in spikes evoked by direct stimulation with short pulses. 2. In either case the inflection becomes less prominent if the motoneuron membrane is depolarized and more prominent when it is hyperpolarized. Both antidromic and direct spikes may fall from the level of the inflection thus evoking a "small spike" only if sufficient hyperpolarization is applied. Similar events occur when antidromic or direct spikes are evoked in the aftermath of a preceding spike. 3. Spikes evoked by direct stimuli applied shortly after firing of a "small spike" may also become partially blocked at a critical stimulus interval. At shorter intervals, however, spike size again increases and no inflection can be detected in the rising phase. 4. When a weak direct stimulus evokes a small spike only, a stronger stimulus may evoke a full spike. Curves of the strength of the stimuli required for eliciting small or full spikes have been constructed in a number of conditions. 5. To explain the results it is assumed that threshold of the major portions of the soma membrane is higher than the threshold of the axon, the transition occurring over a finite area near the axon hillock. Following antidromic or direct stimulation, soma excitation is then initiated in the region of the axon hillock. Spread of activity towards the soma occurs at first slowly and with low safety factor. At this stage block may be easily evoked. Safety factor for propagation increases rapidly as the growing impulse involves larger and larger areas of the soma membrane so that, once the critical areas are excited, activation of the remaining portions of the soma membrane will suddenly occur.
290Â citations
"Electrical properties of the pacema..." refers methods in this paper
...In the present paper, the initial part of the action potential will be called A spike, and the later part B spike, in accordance with the notation adopted by Fuortes, Frank, and Becker (1957)....
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