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.
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TL;DR: An overview of studies on the decapod crustacean cardiac ganglion is given emphasizing contributions to questions of general interest in cellular neurophysiology and continuing to raise new questions for which the ganglions offers excellent research material.
62 citations
TL;DR: GA in concentrations of 10−4 M appears to mimic stimulation of the cardio-inhibitory nerves in every way and decreases the frequency of the bursts of the ganglionic discharge, the length of the discharge and the number of units firing in a discharge.
40 citations
TL;DR: It is concluded that the acceleratory effect is not mediated by the EPSP but is due to a direct action of the transmitter on the pacemaker membrane.
Abstract: The pacemaker neurons of the heart ganglion are innervated from the CNS through two pairs of acceleratory nerves. The effect of acceleratory nerve stimulation was examined with intracellular electrodes from the pacemaker cells. The major effects on the pacemaker potential were an increase in the rate of rise of the spontaneous depolarization and in the duration of the plateau. The aftereffect of stimulation could last for minutes. No clear excitatory postsynaptic potential (EPSP) was observed, however. On high frequency stimulation, a small depolarizing response (the initial response) was sometimes observed, but the major postsynaptic event was the following slow depolarization, or the enhancement of the pacemaker potential (the late response). With hyperpolarization the initial response did not significantly change its amplitude, but the late response disappeared, showing that the latter has the property of the local response. The membrane conductance did not increase with acceleratory stimulation. The injection of depolarizing current increased the rate of rise of the spontaneous depolarization, but only slightly in comparison with acceleratory stimulation, and did not increase the burst duration. It is concluded that the acceleratory effect is not mediated by the EPSP but is due to a direct action of the transmitter on the pacemaker membrane.
36 citations
Cites background or methods or result from "Electrical properties of the pacema..."
...The effect of inhibitory nerve stimulation on the pacemaker activity has been described in a previous paper (Watanabe, Obara, and Akiyama, 1968)....
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...The anatomy of the preparation is described in detail in previous papers (Watanabe, Obara, Akiyama, and Yumoto, 1967; Watanabe, Obara, and Akiyama, 1968)....
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...Neurons in the pacemaker region are electrotonically connected (Watanabe, Obara, Akiyama, and Yumoto, 1967) and therefore potential changes observed in one soma are influenced by those in neighboring somata....
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...We consider the small prepotential to be a spike of dendrites of the penetrated neuron, as has been discussed in a previous paper (Watanabe, Obara, Akiyama, and Yumoto, 1967)....
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...Apart from the stimulus artefact and the externally recorded axon spikes, the appearance of the small prepotential (see Watanabe, Obara, Akiyama, and Yumoto, 1967, p. 831) sometimes posed a confusing problem....
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TL;DR: In this paper, the breathing rhythm-generation mechanism was studied throughout the entire body of the adult lamperey, Entosphenus japonicus, with the body fixed by a specially-designed holder.
Abstract: 1. The breathing rhythm-generation mechanism was studied throughout the entire body of the adult lamperey, Entosphenus japonicus, with the body fixed by a specially-designed holder.2. After brain-stem transection, the rostral part (pontine area) and the caudal part of the medulla (Fig. 2) were found not essential for the generation of respiratory rhythm: the location of the medullary respiratory rhythm-generator was in the district limited by two crosssection lines (Fig. 2).3. Complete division of the brain-stem into two halves by midline section revealed that both of the two symmetrical halves could function independently with their own frequencies for 2 hr or longer.4. Respiratory burst discharges were recorded from the isolated medial part of the medulla, preceded by a so-called diastolic slow depolarization. The forms of these neural activities resemble those reported in pacemaker cells in some crustacean heart ganglion. No periodic discharges correlating exclusively to the relaxation and/or resting period of branchial muscle were observed.5. The reciprocal inhibition model was not necessarily considered a prerequisite for medullary respiratory rhythm-generation in the lamprey.
34 citations
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512 citations
369 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.
332 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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317 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.
290 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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