Glial potentials in hippocampus

1987 ◽  
Vol 65 (5) ◽  
pp. 847-855 ◽  
Author(s):  
J. Casullo ◽  
K. Krnjević
Keyword(s):  
Action Potentials ◽  
Electrical Coupling ◽  
Low Frequency ◽  
Total Absence ◽  
Synaptic Potentials ◽  
Septal Stimulation ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation ◽  
The Mean ◽  
Urethane Anaesthesia

In rats under urethane anaesthesia, intracellular recordings were made from 36 cells, mainly in CA1, that had all the characteristics of glia: unusually high and stable resting potentials (−79.6 ± 6.0 mV, mean ± SD) and total absence of spikes or synaptic potentials. They were exceptionally sensitive to surrounding neuronal activity, being readily depolarized by very low frequency stimulation (0.5-2 Hz) of the fimbria. In the range 0.5–2 Hz, the mean peak depolarizations increased linearly with frequency of fimbrial stimulation (9.1 ± 0.53 mV/Hz). At frequencies of 5 Hz or more, the depolrizations were highly variable, sometimes reaching a maximum of 25–30 mV, but the overall mean was not significantly greater than for 2 Hz stimulation. The depolarizations decayed slowly, with a half-time of 4.2 ± 1.22 s and were often followed by a prolonged undershoot (lasting over 1 min). Alvear and especially septal stimulation were much less effective in evoking glial depolarizations. One cell that initially had all the characteristics of a glia, during very prolonged stable recording, developed responses, such as synaptic potentials and 20–40 mV action potentials evoked by fimbrial or alvear stimulation, consistent with strong electrical coupling to at least one neighbouring neuron.

scholarly journals Lambert-Eaton syndrome without an identified neoplasm

2021 ◽  
Author(s):  
Ana Cláudia Pires Carvalho ◽  
Stella Angelis Trivellato ◽  
Guilherme Jardini Drumond Anastacio ◽  
Fernanda Rezende Dias ◽  
Luisa Crevelin Costa ◽  
...  
Keyword(s):  
Neuromuscular Junction ◽  
Action Potentials ◽  
Low Frequency ◽  
Diagnostic Methods ◽  
Lower Limbs ◽  
High Frequency Stimulation ◽  
Voltage Gated Calcium Channels ◽  
Low Frequency Stimulation ◽  
Compound Muscle Action Potentials ◽  
Frequency Stimulation

Introduction: Lambert-Eaton syndrome occurs due to the attack of autoantibodies to voltage-gated calcium channels in the presynaptic terminal of the neuromuscular junction and is usually paraneoplastic. Objectives: Describe the case of a patient with weakness which was investigated for neoplasm. Design and setting: Case report Methods: Analysis of medical record, photographic record of the diagnostic methods and literature review. Case description: Woman, 60 years old, diabetic, hypertensive and ex-smoker, with proximal weakness in the lower limbs for 4 months with paresthesia in the extremities. In 2 months she needed a cane due to frequent falls, followed by proximal weakness of the upper limbs. She lost 8 kg in 4 months. Neurological examination showed hypotrophy in thighs, proximal tetraparesis predominantly in lower limbs and global hyporeflexia. Electroneuromyography showed decreases to repetitive low-frequency stimulation, but significant increases with repetitive high-frequency stimulation and increased amplitude of compound muscle action potentials after effort, suggesting impairment of the neuromuscular junction in the presynaptic topography. She was diagnosed with LambertEaton syndrome. An investigation of paraneoplastic syndrome was carried out, with tumor markers, tomography of the chest, abdomen and pelvis, thyroid ultrasound, mammography and oncotic colposcopy, all without findings of neoplasia. It was proposed a treatment with human immunoglobulin and followup with physiotherapy, occupational therapy and psychology. She showed a significant improvement in strength after starting treatment. Conclusion: Patients with Lambert-Eaton syndrome should be investigated for an underlying neoplasm and followed up periodically, considering the possibility of cancer diagnosis even months or years after the neurological syndrome.

Fatigue and damage to the masseter muscle by prolonged low-frequency stimulation in the rat

2005 ◽  
Vol 50 (12) ◽  
pp. 1005-1013 ◽  
Author(s):  
Konosuke Yamasaki ◽  
Shuitsu Harada ◽  
Itsuro Higuchi ◽  
Mitsuhiro Osame ◽  
Gakuji Ito
Keyword(s):  
Masseter Muscle ◽  
Low Frequency ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation

scholarly journals MONOSYNAPTIC REFLEX RESPONSE OF INDIVIDUAL MOTONEURONS AS A FUNCTION OF FREQUENCY

1957 ◽  
Vol 40 (3) ◽  
pp. 435-450 ◽  
Author(s):  
David P. C. Lloyd
Keyword(s):  
High Frequency ◽  
Temporal Summation ◽  
Low Frequency ◽  
Stimulation Frequency ◽  
Monosynaptic Reflex ◽  
Reflex Response ◽  
High Frequency Stimulation ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation ◽  
Frequency Of Stimulation

An assemblage of individual motoneurons constituting a synthetic motoneuron pool has been studied from the standpoint of relating monosynaptic reflex responses to frequency of afferent stimulation. Intensity of low frequency depression is not a simple function of transmitter potentiality. As frequency of stimulation increases from 3 per minute to 10 per second, low frequency depression increases in magnitude. Between 10 and approximately 60 per second low frequency depression apparently diminishes and subnormality becomes a factor in causing depression. At frequencies above 60 per second temporal summation occurs, but subnormality limits the degree of response attainable by summation. At low stimulation frequencies rhythm is determined by stimulation frequency. Interruptions of rhythmic firing depend solely upon temporal fluctuation of excitability. At high frequency of stimulation rhythm is determined by subnormality rather than inherent rhythmicity, and excitability fluctuation leads to instability of response rhythm. In short, whatever the stimulation frequency, random excitability fluctuation is the factor disrupting rhythmic response. Monosynaptic reflex response latency is stable during high frequency stimulation as it is in low frequency stimulation provided a significant extrinsic source of random bombardment is not present. In the presence of powerful random bombardment discharge may become random with respect to monosynaptic afferent excitation provided the latter is feeble. When this occurs it does so equally at low frequency and high frequency. Thus temporal summation is not a necessary factor. There is, then, no remaining evidence to suggest that the agency for temporal summation in the monosynaptic system becomes a transmitting agency in its own right.

Effects of low-frequency stimulation of the superior colliculus on spontaneous and visually guided saccades

1993 ◽  
Vol 69 (3) ◽  
pp. 953-964 ◽  
Author(s):  
P. W. Glimcher ◽  
D. L. Sparks
Keyword(s):  
Superior Colliculus ◽  
Time Course ◽  
Low Frequency ◽  
Arbitrary Point ◽  
Visually Guided ◽  
Spontaneous Movements ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation ◽  
Stimulation Current ◽  
Stimulation Of

1. The first experiment of this study determined the effects of low-frequency stimulation of the monkey superior colliculus on spontaneous saccades in the dark. Stimulation trains, subthreshold for eliciting short-latency fixed-vector saccades, were highly effective at biasing the metrics (direction and amplitude) of spontaneous movements. During low-frequency stimulation, the distribution of saccade metrics was biased toward the direction and amplitude of movements induced by suprathreshold stimulation of the same collicular location. 2. Low-frequency stimulation biased the distribution of saccade metrics but did not initiate movements. The distribution of intervals between stimulation onset and the onset of the next saccade did not differ significantly from the distribution of intervals between an arbitrary point in time and the onset of the next saccade under unstimulated conditions. 3. Results of our second experiment indicate that low-frequency stimulation also influenced the metrics of visually guided saccades. The magnitude of the stimulation-induced bias increased as stimulation current or frequency was increased. 4. The time course of these effects was analyzed by terminating stimulation immediately before, during, or after visually guided saccades. Stimulation trains terminated at the onset of a movement were as effective as stimulation trains that continued throughout the movement. No effects were observed if stimulation ended 40–60 ms before the movement began. 5. These results show that low-frequency collicular stimulation can influence the direction and amplitude of spontaneous or visually guided saccades without initiating a movement. These data are compatible with the hypothesis that the collicular activity responsible for specifying the horizontal and vertical amplitude of a saccade differs from the type of collicular activity that initiates a saccade.

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