The Initiation of Action Potentials in the Somatic Musculature of Ascaris Lumbricoides

1967 ◽  
Vol 46 (2) ◽  
pp. 263-279
Author(s):  
J. DEL CASTILLO ◽  
W. C. DE MELLO ◽  
T. MORALES
Keyword(s):  
Membrane Potential ◽  
Direct Current ◽  
Action Potentials ◽  
Safety Margin ◽  
Nerve Fibres ◽  
Muscle Belly ◽  
Single Action ◽  
Somatic Musculature ◽  
Spike Firing ◽  
Stimulation Of

1. The site and mechanism of initiation of the rhythmic action potentials controlling the somatic musculature of Ascaris have been reinvestigated. 2. Polarization of the muscle syncytium by direct current injection revealed little accommodation. Action potentials are generated continuously at this region at a frequency which depends on the membrane potential. 3. Excitatory and inhibitory nerve fibres control the membrane potential of the syncytial membrane and, therefore, the frequency of spike firing. The effects of stimulation of these fibres are described. 4. The resumption of electrical activity when cooled, quiescent preparations were warmed up was studied. The first signs of activity are slow rhythmic depolarizations on which bursts of abortive spikes are superimposed. When the amplitude of the transients in each burst increases sufficiently they unite into a large, single action potential. 5. Evidence is presented suggesting that each of the abortive spikes represents the separate, subthreshold excitation of one of the terminal branches of the muscle arm, due to a low safety margin for the conduction of impulses towards the muscle belly. 6. Small (1-2 mV.) spontaneous, apparently random, depolarizations and hyperpolarizations have been recorded with microelectrodes inserted into the syncytial region. Their possible synaptic origin is discussed.

Structure and Function of the Lateral Giant Neurone of the Primitive Crustacean Anaspides Tasmaniae

1979 ◽  
Vol 78 (1) ◽  
pp. 121-136
Author(s):  
GERALD E. SILVEY ◽  
IAN S. WILSON
Keyword(s):  
Action Potentials ◽  
Tactile Stimulation ◽  
Large Diameter ◽  
Whole Body ◽  
Giant Fibre ◽  
Single Action ◽  
Giant Neurone ◽  
And Function ◽  
Thoracic And Abdominal ◽  
Stimulation Of

The syncarid crustacean Anaspides tasmaniae rapidly flexes its free thoracic and abdominal segments in response to tactile stimulation of its body. This response decrements but recovers in slightly more than one hour. The fast flexion is evoked by single action potentials in the lateral of two large diameter fibres (40 μm) which lie on either side of the cord. The lateral giant fibre is made up of fused axons of 11 neurones, one in each of the last 5 thoracic and 6 abdominal ganglia. The soma of each neurone lies contralateral to the axon. Its neurite crosses that of its counterpart in the commissure and gives out dendrites into the neuropile of each hemiganglion. The lateral giant neurone receives input from the whole body but fires in response only to input from the fourth thoracic segment posteriorly. Both fibres respond with tactile stimulation of only one side. Since neither current nor action potentials spread from one fibre to the other, afferents must synapse with both giant neurones. The close morphological and physiological similarities of the lateral giant neurone in Anaspides to that in the crayfish (Eucarida) suggest that the lateral giant system arose in the ancestor common to syncarids and eucarids, prior to the Carboniferous.

Unit Activity in the Abdominal Nerve Cord of a Dragonfly NYMPH

1962 ◽  
Vol 39 (1) ◽  
pp. 31-44
Author(s):  
ANN FIELDEN ◽  
G. M. HUGHES
Keyword(s):  
Action Potentials ◽  
The Body ◽  
Peripheral Stimulus ◽  
Inhibitory Effects ◽  
Nerve Fibres ◽  
Dragonfly Nymph ◽  
Peripheral Area ◽  
Segmental Ganglion ◽  
Peripheral Areas ◽  
Stimulation Of

1. Electrical activity of single units has been studied in small bundles of nerve fibres split off from the connectives between abdominal ganglia of the dragonfly nymph. Many units showed a resting discharge but activity of other units was only found when the insect was stimulated mechanically. 2. In some fibres the resting discharge was unaffected by mechanical stimulation and such spontaneous activity showed different patterns. These units were identified as interneurones and a prominent feature of their discharge was an irregular firing over long periods and the formation of characteristic intermittent bursts. 3. Responses to tactile or proprioceptive stimulation were investigated in primary sensory fibres and interneurones. The latter showed excitatory and inhibitory effects which were often related to the site of the peripheral stimulus. 4. Primary sensory fibres generally gave action potentials of smaller amplitude and were excited by stimulation of more localized areas. Many fibres traverse at least one connective after they enter a segmental ganglion and most ascend or descend ipsilaterally, but some crossing-over of sensory fibres occurs in the ganglia. 5. Interneurones were classified according to the nature of the peripheral areas from which they received their input. Ipsilateral, contralateral, and bilateral fibres have all been found but so far there is no evidence for any asymmetric fibres. Fibres responding to stimulation of a single segment or of many segments were found. Some of the latter extended over the whole length of the body and it is clear that spikes may be initiated in many of the ganglia through which an interneurone passes. 6. It is evident from this work that a given peripheral area is represented centrally by many interneurones and a great deal of convergence from different areas may occur on individual interneurones.

scholarly journals VAGAL AND SYMPATHETIC EFFECTS ON THE PACEMAKER FIBERS IN THE SINUS VENOSUS OF THE HEART

1956 ◽  
Vol 39 (5) ◽  
pp. 715-733 ◽  
Author(s):  
Otto F. Hutter ◽  
Wolfgang Trautwein
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Action Potentials ◽  
Vagal Stimulation ◽  
Sinus Venosus ◽  
Sympathetic Stimulation ◽  
Pacemaker Potential ◽  
Pacemaker Potentials ◽  
Different Parts ◽  
Stimulation Of

1. Action potentials from sinus venosus and auricle fibers of spontaneously beating frog hearts have been recorded with intracellular electrodes. 2. Sinus fibers show a slow depolarization, the pacemaker potential, during diastole. The amplitude of this potential varies in different parts of the sinus. In some fibers the membrane potential falls by 11 to 15 mv. during diastole and the transition to the upstroke of the action potential is comparatively gradual. In other regions the depolarization develops more slowly and the action potential takes off more abruptly from a higher membrane potential. It is proposed that the fibers showing the largest fall in membrane potential during diastole are the pacemaker fibers of the heart, and that the rest of the preparation is excited by conduction. In auricle fibers the membrane potential is constant during diastole. 3. The maximum diastolic membrane potential and the overshoot of the action potential vary inversely with the amplitude of the pacemaker potential. The highest values were measured in auricle fibers. 4. Stimulation of vagi suppresses the pacemaker potentials. While the heart is arrested the membrane potential of the sinus fibers rises to a level above the maximum diastolic value reached in previous beats. In 28 experiments vagal stimulation increased the membrane potential from an average maximal diastolic value of 55 mv. to a "resting" level of 65.4 mv. The biggest vagal polarization was 23 mv. 5. In contrast to the sinus fibers vagal inhibition does not change the diastolic membrane potential of frog auricle fibers. 6. Vagal stimulation greatly accelerates the repolarization of the action potential and reduces its amplitude. These changes were seen both in the sinus and in auricle fibers stimulated by direct shocks during vagal arrest. 7. The conduction velocity in the sinus venosus of the tortoise is reduced by vagal stimulation. Block of conduction often occurs. 8. In the frog sinus venosus sympathetic stimulation increases the rate of rise of the pacemaker potential, accelerating the beat. The threshold remains unchanged. The rate of rise of the upstroke and the amplitude of the overshoot are increased. 9. The analogies between the vagal inhibition of the heart and the nervous inhibition of other preparations are discussed.

Failure of Averaging in the Construction of a Conductance-Based Neuron Model

2002 ◽  
Vol 87 (2) ◽  
pp. 1129-1131 ◽  
Author(s):  
Jorge Golowasch ◽  
Mark S. Goldman ◽  
L. F. Abbott ◽  
Eve Marder
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Action Potentials ◽  
Neuron Model ◽  
Model Neuron ◽  
Maximal Conductance ◽  
Single Action ◽  
Bursting Neurons ◽  
Voltage Dependent ◽  
Multiple Samples

Parameters for models of biological systems are often obtained by averaging over experimental results from a number of different preparations. To explore the validity of this procedure, we studied the behavior of a conductance-based model neuron with five voltage-dependent conductances. We randomly varied the maximal conductance of each of the active currents in the model and identified sets of maximal conductances that generate bursting neurons that fire a single action potential at the peak of a slow membrane potential depolarization. A model constructed using the means of the maximal conductances of this population is not itself a one-spike burster, but rather fires three action potentials per burst. Averaging fails because the maximal conductances of the population of one-spike bursters lie in a highly concave region of parameter space that does not contain its mean. This demonstrates that averages over multiple samples can fail to characterize a system whose behavior depends on interactions involving a number of highly variable components.

scholarly journals Distinctive Neurophysiological Properties of Embryonic Trigeminal and Geniculate Neurons in Culture

2002 ◽  
Vol 88 (4) ◽  
pp. 2058-2074 ◽  
Author(s):  
Arturas Grigaliunas ◽  
Robert M. Bradley ◽  
Donald K. MacCallum ◽  
Charlotte M. Mistretta
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Action Potentials ◽  
Resting Membrane Potential ◽  
Target Tissue ◽  
Extrinsic Factors ◽  
Single Action ◽  
Trigeminal Neurons ◽  
Ganglion Neurons ◽  
Passive Membrane

Neurons in trigeminal and geniculate ganglia extend neurites that share contiguous target tissue fields in the fungiform papillae and taste buds of the mammalian tongue and thereby have principal roles in lingual somatosensation and gustation. Although functional differentiation of these neurons is central to formation of lingual sensory circuits, there is little known about electrophysiological properties of developing trigeminal and geniculate ganglia or the extrinsic factors that might regulate neural development. We used whole cell recordings from embryonic day 16 rat ganglia, maintained in culture as explants for 3–10 days with neurotrophin support to characterize basic properties of trigeminal and geniculate neurons over time in vitro and in comparison to each other. Each ganglion was cultured with the neurotrophin that supports maximal neuron survival and that would be encountered by growing neurites at highest concentration in target fields. Resting membrane potential and time constant did not alter over days in culture, whereas membrane resistance decreased and capacitance increased in association with small increases in trigeminal and geniculate soma size. Small gradual differences in action potential properties were observed for both ganglion types, including an increase in threshold current to elicit an action potential and a decrease in duration and increase in rise and fall slopes so that action potentials became shorter and sharper with time in culture. Using a period of 5–8 days in culture when neural properties are generally stable, we compared trigeminal and geniculate ganglia and revealed major differences between these embryonic ganglia in passive membrane and action potential characteristics. Geniculate neurons had lower resting membrane potential and higher input resistance and smaller, shorter, and sharper action potentials with lower thresholds than trigeminal neurons. Whereas all trigeminal neurons produced a single action potential at threshold depolarization, 35% of geniculate neurons fired repetitively. Furthermore, all trigeminal neurons produced TTX-resistant action potentials, but geniculate action potentials were abolished in the presence of low concentrations of TTX. Both trigeminal and geniculate neurons had inflections on the falling phase of the action potential that were reduced in the presence of various pharmacological blockers of calcium channel activation. Use of nifedipine, ω-conotoxin-MVIIA and GVIA, and ω-agatoxin-TK indicated that currents through L-, N-, and P/Q- type calcium channels participate in the action potential inflection in embryonic trigeminal and geniculate neurons. The data on passive membrane, action potential, and ion channel characteristics demonstrate clear differences between trigeminal and geniculate ganglion neurons at an embryonic stage when target tissues are innervated but receptor organs have not developed or are still immature. Therefore these electrophysiological distinctions between embryonic ganglia are present before neural activity from differentiated receptive fields can influence functional phenotype.

Role of sarcolemma action potentials and excitability in muscle fatigue

1994 ◽  
Vol 76 (5) ◽  
pp. 2157-2162 ◽  
Author(s):  
E. M. Balog ◽  
L. V. Thompson ◽  
R. H. Fitts
Keyword(s):  
Membrane Potential ◽  
Action Potentials ◽  
Stimulation Frequency ◽  
Resting Membrane Potential ◽  
Stimulation Protocol ◽  
Semitendinosus Muscle ◽  
Fusion Frequency ◽  
Before And After ◽  
Stimulation Of

The purposes of this study were to characterize the alterations in the sarcolemma action potential (AP) waveform and sarcolemma excitability as a result of fatiguing stimulation of the frog semitendinosus muscle and to relate these changes to the decrease in the force-generating ability of the muscle. Trains of APs were recorded before and after stimulation (100-ms trains, 150 Hz, 1/s for 5 min). The resting membrane potential (RMP), AP overshoot (OS), and duration at 50% of peak magnitude (DUR) were -84.3 +/- 2.0 mV, 19.5 +/- 1.9 mV, and 1.3 +/- 0.1 ms, respectively, before stimulation. The stimulation protocol caused RMP to depolarize to -75.1 +/- 2.0 mV, OS to fall to 7.3 +/- 1.9 mV, and DUR to increase to 2.5 +/- 0.4 ms. RMP and OS recovered fully in 5 min after the cessation of stimulation, whereas DUR was still prolonged. Before the stimulation protocol, AP frequency matched the stimulation frequency at all stimulation rates < or = 150 Hz. At 200-Hz stimulation, AP frequency was 192 +/- 6 Hz. After 5 min of stimulation, AP frequency matched the stimulation frequency only at < or = 60 Hz. At 100-, 150-, and 200-Hz stimulation, AP frequencies were 89 +/- 8, 84 +/- 17, and 79 +/- 15 Hz, respectively. Because of a decreased fusion frequency at fatigue, the fall in the sarcolemma AP frequency did not contribute to the decreased force. The stimulation-induced alterations in the AP waveform were moderate and unlikely to have caused fatigue. However, the alterations in AP may have been more extreme in the depths of the transverse tubules.

Limbic Gamma Rhythms. II. Synaptic and Intrinsic Mechanisms Underlying Spike Doublets in Oscillating Subicular Neurons

1998 ◽  
Vol 80 (1) ◽  
pp. 162-171 ◽  
Author(s):  
Ian M. Stanford ◽  
Roger D. Traub ◽  
John G. R. Jefferys
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Action Potentials ◽  
Gamma Oscillations ◽  
Gamma Oscillation ◽  
Population Spike ◽  
Tetanic Stimulation ◽  
Single Action ◽  
Gamma Rhythms ◽  
Afferent Volleys

Stanford, Ian M., Roger D. Traub, and John G. R. Jefferys. Limbic gamma rhythms. II. Synaptic and intrinsic mechanisms underlying spike doublets in oscillating subicular neurons. J. Neurophysiol. 80: 162–171, 1998. Gamma oscillations were evoked in the subiculum in rat transverse hippocampal slices by tetanic stimulation (200 ms/100 Hz) of either CA1 or subiculum. Gamma oscillations in the subiculum differed from those in CA1 in containing population spike doublets as well as singlets. The present study addresses the origin of this more complex form of gamma oscillation in the subiculum. Intracellular recordings from subicular neurons revealed that 63% of them fired double action potentials on cycles of the gamma oscillation that generated population spike doublets after tetanic stimulation of either CA1 or subiculum. The remaining cells produced excitatory postsynaptic potentials (EPSPs), and occasional single spikes, on each cycle. Neurons that fired occasional single action potentials during gamma rhythms were “regular spiking” cells. They did not produce burst discharges during depolarizing steps, had minimal membrane potential sags on hyperpolarizing steps, and responded to single afferent volleys with a single action potential on an EPSP followed by a large inhibitory postsynaptic potential complex. Fast spiking cells were observed too infrequently to be studied in detail. Neurons that fired doublets during gamma rhythms were “intrinsic burst” (IB) cells. They generated bursts of action potentials on step membrane depolarizations, had significant membrane potential sags on step hyperpolarizations with an anodal break potential on return to rest, and fired multiple action potentials in response to high-intensity single afferent volleys. IB neurons did not fire action potential doublets during 1-s membrane depolarizations. Double action potentials, however, were evoked in these cells by depolarizing pulses at 40 Hz from hyperpolarized membrane potentials (−100 mV). Computer simulations suggest that the hyperpolarization between the depolarizations was essential for action potential doublets. The results in this and the previous paper suggest the following: either CA1 or subiculum alone can generate gamma oscillations gated by local networks of interneurons, oscillations in CA1 project through pyramidal cell axons to subiculum with a time lag expected from axon conduction delays, and oscillating sequences of EPSPs and intrinsic and/or synaptic hyperpolarizing potentials in IB subicular neurons generate gamma frequency spike doublets, which depend on both the intrinsic properties of these neurons and their temporally patterned synaptic input. This phenomenon could amplify gamma output from CA1 and modify its coupling to gamma oscillations in the wider limbic system.

Intracellular study of electrophysiological features of primate spinothalamic tract neurons and their responses to afferent inputs

1991 ◽  
Vol 65 (6) ◽  
pp. 1554-1566 ◽  
Author(s):  
D. X. Zhang ◽  
C. M. Owens ◽  
W. D. Willis
Keyword(s):  
Electrical Stimulation ◽  
Membrane Potential ◽  
Action Potentials ◽  
Dynamic Range ◽  
Background Activity ◽  
Resting Membrane Potential ◽  
Spinothalamic Tract ◽  
Spontaneous Rate ◽  
Afferent Inputs ◽  
Stimulation Of

1. Intracellular recordings were made from 43 spinothalamic (STT) neurons in the lumbosacral region of the spinal cord in anesthetized macaque monkeys. The antidromic responses of these neurons to electrical stimulation of the ventral posterior lateral (VPL) nucleus of the thalamus were examined, and orthodromic responses to electrical stimulation of the sural nerve or to mechanical stimulation of hindlimb skin were recorded to study the electrophysiological features of these neurons and their responses to afferent inputs. 2. The resting membrane potential of the neurons ranged from -26 to -70 mV and the antidromic latency from 2.3 to 9.1 ms. Three of the neurons were located in lamina 1 and were recorded so briefly that only antidromic and spontaneous activity could be studied. The rest of the neurons were located in laminae III-V and were of the wide-dynamic-range (WDR) type. 3. The antidromic action potentials recorded in the somas of STT neurons typically showed a fast rising phase and a short initial segment-somadendritic (IS-SD) delay. After repetitive antidromic stimulation, a progressive elongation of the IS-SD delay, widening of the spike, and failure of the SD spike were observed. 4. The afterpotential of the antidromic action potential consisted of a fast afterhyperpolarization (AHPf) and sometimes a delayed depolarization (DD) and a slow afterhyperpolarization (AHPs). The amplitude and the duration of the AHPs were progressively increased when longer trains of stimuli were used. When the membrane potential was hyperpolarized, the amplitude of the AHPs decreased, suggesting an involvement of K+ and/or Cl- ions. However, the AHPs completely disappeared when the strength of stimulation was adjusted to a level just below the threshold for the axon, suggesting that it was unlikely that recurrent inhibition contributed to the AHPs. 5. The background activity of 32 STT neurons was analyzed. The membrane potential at which spikes were triggered in these neurons was around -42 mV. The width and the rise time of the spontaneous spikes were shorter than those of antidromic action potentials, although the maximum rate of rise was similar. The heights of the spontaneous spikes were slightly shorter than those of antidromic action potentials. 6. Three types of background activity have been observed. One type had a very low average spontaneous rate with a bursting firing pattern, consisting of a few spikes superimposed on a depolarization. This type of activity was seen mostly in lamina I neurons. The second type of activity had a moderate to high spontaneous rate with a fairly constant interval between spikes.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition of paraventricular neurons by subfornical organ and AV3V in cats

1988 ◽  
Vol 255 (6) ◽  
pp. R961-R967 ◽  
Author(s):  
T. Osaka ◽  
H. Yamashita ◽  
K. Koizumi
Keyword(s):  
Electrical Stimulation ◽  
Action Potentials ◽  
Subfornical Organ ◽  
Chemical Stimulation ◽  
Large Animal ◽  
Lamina Terminalis ◽  
Sodium Glutamate ◽  
Pentobarbital Sodium ◽  
Single Action ◽  
Stimulation Of

The study was designed to examine, by electrophysiological techniques, influences of rostral periventricular structures on neurons in the hypothalamic paraventricular nucleus (PVN) in a large animal (the cat) in which stimulating and recording sites could be precisely identified. Extracellular single action potentials were recorded from the PVN in pentobarbital sodium-anesthetized and hemispherectomized cats. Of 246 neurons tested, 24-47% were inhibited and 9-21% were excited by electrical stimulation of the subfornical organ (SFO), the nucleus preopticus medianus (POMn), and the organum vasculosum of the lamina terminalis (OVLT). The onset latencies of inhibition (19-26 ms) were shorter than those of excitation (28-80 ms). Responses of both neurosecretory and nonneurosecretory neurons were similar to the stimulation of all sites tested. Among these sites, the POMn had the strongest influence on the PVN in view of the proportion of the responsive neurons. Moreover, antidromically evoked action potentials in the PVN neurons (n = 10) were only observed after stimulation of the POMn. Chemical stimulation of POMn and SFO by microinjection of sodium glutamate (50-100 nl, 0.5 M) also inhibited 16 of 38 PVN cells; the remaining neurons were unaffected. These results suggest that activation of the POMn, OVLT, and the SFO neurons mainly inhibits the PVN neurons in the cat.

Neuronal Mechanisms Underlying the Laryngeal Adductor Reflex

2011 ◽  
Vol 120 (11) ◽  
pp. 755-760 ◽  
Author(s):  
Qi-Jian Sun ◽  
Jia Min Chum ◽  
Tara G. Bautista ◽  
Paul M. Pilowsky ◽  
Robert G. Berkowitz
Keyword(s):  
Action Potentials ◽  
Superior Laryngeal Nerve ◽  
Laryngeal Nerve ◽  
Short Latency ◽  
Occurrence Rate ◽  
Sprague Dawley ◽  
Single Action ◽  
Long Latency ◽  
Laryngeal Adductor Reflex ◽  
Stimulation Of

Objectives: Electromyographic studies of the laryngeal adductor reflex, glottal closure occurring in response to laryngeal stimulation, have demonstrated an early ipsilateral response (R1) and a late bilateral response (R2). To better define the physiologic properties of these responses, we recorded responses from expiratory laryngeal motoneurons (ELMs) in rats during stimulation of the superior laryngeal nerve (SLN). Methods: Single unit extracellular recordings were obtained from 5 ELMs, identified by their antidromic responses to recurrent laryngeal nerve stimulation and postinspiratory firing pattern, in 4 Sprague-Dawley rats. Results: Unilateral stimulation of the SLN (at 20 Hz) stopped both phrenic nerve inspiratory activity and ELM postinspiratory activity. However, the ELMs displayed robust tonic firing, consisting of non-respiratory burst activity and single action potentials. The single action potentials were identified as short-latency ones (5 to 10 ms) activated by ipsilateral SLN stimulation, with an occurrence rate of 90%, and long-latency ones (20 to 50 ms) activated by bilateral SLN stimulation, with occurrence rates of 47% on the ipsilateral side and 58% on the contralateral side. Conclusions: The R1 response appears to be the result of the short-latency action potentials, orthodromically activated by ipsilateral stimulation of the SLN. The R2 response is likely to be a result of the long-latency action potentials that can be recorded from ELMs on both sides.

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