Short-range stiffness of slow fibers and twitch fibers in reptilian muscle

The semitendinous muscle of the lizard Tilique contains both slow and twitch fibers; by subdivision of its motor nerve, fibers of each type may be stimulated separately. When, during repetitive stimulation of nerve filaments, the muscle was lengthened or shortened, the tension changes included an initial short-range stiffness, followed by a later compliance. With increasing velocities of movement, the short-range stiffness increased toward a limiting value. For slow fibers this limiting value was reached with lower velocities of movement than for the twitch fibers. Provided that the same velocity of movement was used and the movements began from similar initial isometric tensions, the slow fibers resisted the movements with a greater stiffness than the twitch fibers. It is suggested that not all of the observed differences between the two fiber types can be interpreted simply in terms of differences in rates of formation and breakdown of cross-links.

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R430 – Glycogen Depletion for Study of Neuromuscular Connectivity

Otolaryngology ◽

10.1016/j.otohns.2008.05.585 ◽

2008 ◽

Vol 139 (2_suppl) ◽

pp. P188-P188

Author(s):

Isamu Kunibe ◽

David L Zealear ◽

Akihiro Katada ◽

Vikas P. Singh ◽

James Bekeny ◽

...

Keyword(s):

Muscle Fibers ◽

Nerve Fibers ◽

Medial Gastrocnemius ◽

Fiber Types ◽

Glycogen Depletion ◽

Steady Rate ◽

Wide Range ◽

Neuromuscular Connectivity ◽

Stimulation Of Nerve ◽

Stimulation Of

Problem A useful technique for characterizing connectivity between nerve and muscle involves prolonged electrical stimulation of nerve fibers to deplete glycogen in their target muscle fibers. Depleted muscle fibers appear blank when stained by the PAS technique. Unfortunately, results are inconsistent over a wide range of stimulus paradigms. The aim of this study was to identify other factors that may impact glycogen depletion. Methods Glycogen depletion was examined in the rat medial gastrocnemius muscle because of the presence of aerobic fiber types I and IIA, which are resistant to depletion. Tension and EMG were monitored during maximal stimulation of transected sciatic nerve with a 333 msec pulse train delivered at 40 Hz every second over a period of 1 hour. Once an effective paradigm was identified, depletion of an entirely aerobic muscle (i.e., soleus) was evaluated. Results Animals maintained in a light plane of anesthesia with a steady rate of pentobarbital IP infusion showed an average depletion of only 72%. Animals administered a progressively increasing level of anesthesia with continued stimulation until complete loss of muscular response showed a significantly greater depletion of 96%. However, when this paradigm was applied to the soleus, only 37% of the muscle depleted. Further investigation determined that co-contraction of gastrocnemius with soleus resulted in unloading of the slower soleus. Disruption of the gastrocnemius insertion on the Achilles tendon shifted the load to the soleus and increased soleus depletion to 93%. Conclusion Muscle fibers of any motor unit type can be identified with 93–96% accuracy when nerve stimulation is applied to an isometrically loaded muscle that is in a state of progressive barbiturate anesthesia. Significance Glycogen depletion provides a method for identifying the number, types, and distribution of muscle fibers in a muscle that have reinnervated, important in the assessment of nerve regeneration. Support NIH grants R01 DC001149 and R01 DC008429.

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Tetanic hyperpolarization of single medullated nerve fibers in sodium and lithium

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1976.231.4.1033 ◽

1976 ◽

Vol 231 (4) ◽

pp. 1033-1038 ◽

Cited By ~ 2

Author(s):

GM Schoepfle

Keyword(s):

Steady State ◽

Interspike Interval ◽

Nerve Fibers ◽

Repetitive Stimulation ◽

Time Dependent ◽

Potassium Ions ◽

Current Densities ◽

Medullated Nerve Fiber ◽

Sodium And Potassium ◽

Stimulation Of

Repetitive stimulation of a single medullated nerve fiber of Xenopus yields a succession of postspike voltage-time curves which are nearly coincident until attainment of a voltage that corresponds to that of the maximum attained by the normal postspike undershoot. Initially the interspike potential returns toward a resting level after this brief phase of hyperpolarization. However, as tetanization proceeds, a pattern of hyperpolarization develops with the result that, in the tetanic steady state, there exists a progressive hyperpolarization throughout each interspike interval. Extent of postspike hyperpolarization in terms of a deviation deltaVm from the resting level of membrane potential is approximated by the variation deltaVm = delta[MNa + MK]/[GNa + GK] where MNa and MK are current densities associated with active pumping of sodium and potassium ions and GNa and GK are corresponding time-dependent leak conductances. Tetanic hyperpolarization is reversibly abolished by cyanide and by exposure to lithium Ringer. Eventual reappearance of tetanic hyperpolarization in the presence of lithium Ringer suggests lithium pumping.

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ATP concentrations and muscle tension increase linearly with muscle contraction

Journal of Applied Physiology ◽

10.1152/japplphysiol.00185.2003 ◽

2003 ◽

Vol 95 (2) ◽

pp. 577-583 ◽

Cited By ~ 92

Author(s):

Jianhua Li ◽

Nicholas C. King ◽

Lawrence I. Sinoway

Keyword(s):

Skeletal Muscle ◽

Electrical Stimulation ◽

Muscle Contraction ◽

Motor Nerve ◽

Muscle Tension ◽

Nerve Fibers ◽

Ventral Root ◽

Ventral Roots ◽

Root Stimulation ◽

Stimulation Of

Previous studies have suggested that activation of ATP-sensitive P2X receptors in skeletal muscle play a role in mediating the exercise pressor reflex (Li J and Sinoway LI. Am J Physiol Heart Circ Physiol 283: H2636–H2643, 2002). To determine the role ATP plays in this reflex, it is necessary to examine whether muscle interstitial ATP (ATPi) concentrations rise with muscle contraction. Accordingly, in this study, muscle contraction was evoked by electrical stimulation of the L7 and S1 ventral roots of the spinal cord in 12 decerebrate cats. Muscle ATPi was collected from microdialysis probes inserted in the muscle. ATP concentrations were determined by the HPLC method. Electrical stimulation of the ventral roots at 3 and 5 Hz increased mean arterial pressure by 13 ± 2 and 16 ± 3 mmHg ( P < 0.05), respectively, and it increased ATP concentration in contracting muscle by 150% ( P < 0.05) and 200% ( P < 0.05), respectively. ATP measured in the opposite control limb did not rise with ventral root stimulation. Section of the L7 and S1 dorsal roots did not affect the ATPi seen with 5-Hz ventral root stimulation. Finally, ventral roots stimulation sufficient to drive motor nerve fibers did not increase ATP in previously paralyzed cats. Thus ATPi is not largely released from sympathetic or motor nerves and does not require an intact afferent reflex pathway. We conclude that ATPi is due to the release of ATP from contracting skeletal muscle cells.

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Efferent Synaptic Transmission at the Vestibular Type II Hair Cell Synapse

10.1101/2020.03.14.992180 ◽

2020 ◽

Author(s):

Zhou Yu ◽

J. Michael McIntosh ◽

Soroush Sadeghi ◽

Elisabeth Glowatzki

Keyword(s):

Hair Cells ◽

Nerve Fibers ◽

Repetitive Stimulation ◽

Vestibular Nerve ◽

Type I ◽

Type Ii ◽

Optogenetic Stimulation ◽

Vestibular Afferents ◽

Stimulation Of

ABSTRACTIn the vestibular peripheral organs, type I and type II hair cells (HCs) transmit incoming signals via glutamatergic quantal transmission onto afferent nerve fibers. Additionally, type I HCs transmit via ‘non-quantal’ transmission to calyx afferent fibers, by accumulation of glutamate and potassium in the synaptic cleft. Vestibular efferent inputs originating in the brainstem contact type II HCs and vestibular afferents. Here, we aimed at characterizing the synaptic efferent inputs to type II HCs using electrical and optogenetic stimulation of efferent fibers combined with in vitro whole-cell patch clamp recording from type II HCs in the rodent vestibular crista. Properties of efferent synaptic currents in type II HCs were similar to those found in cochlear hair cells and mediated by activation of α9/α10 nicotinic acetylcholine receptors (AChRs) and SK potassium channels. While efferents showed a low probability of release at low frequencies of stimulation, repetitive stimulation resulted in facilitation and increased probability of release. Notably, the membrane potential of type II HCs measured during optogenetic stimulation of efferents showed a strong hyperpolarization even in response to single pulses and was further enhanced by repetitive stimulation. Such efferent-mediated inhibition of type II HCs can provide a mechanism to adjust the contribution of signals from type I and type II HCs to vestibular nerve fibers. As a result, the relative input of type I hair cells to vestibular afferents will be strengthened, emphasizing the phasic properties of the incoming signal that are transmitted via fast non-quantal transmission.New and NoteworthyType II vestibular hair cells (HCs) receive inputs from efferent fibers originating in the brainstem. We used in vitro optogenetic and electrical stimulation of efferent fibers to study their synaptic inputs to type II HCs. Efferent inputs inhibited type II HCs, similar to cochlear efferent effects. We propose that efferent inputs adjust the contribution of signals from type I and type II HCs that report different components of the incoming signal to vestibular nerve fibers.

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CONDUCTION BLOCK OF TERMINAL SOMATIC MOTOR FIBERS IN TICK PARALYSIS

Canadian Journal of Biochemistry and Physiology ◽

10.1139/o60-031 ◽

1960 ◽

Vol 38 (3) ◽

pp. 287-295 ◽

Cited By ~ 9

Author(s):

Maurice F. Murnaghan

Keyword(s):

Motor Nerve ◽

Conduction Block ◽

Nerve Impulse ◽

Nerve Fibers ◽

Treated Animal ◽

Direct Stimulation ◽

High Potassium ◽

Control Value ◽

Choline Acetylase ◽

Stimulation Of

In the perfused anterior tibial muscle of the tick-paralyzed dog acetylcholine in excess of the control value is not liberated on stimulation of the peroneal nerve; in the normal muscle 7 μμg of acetylcholine is liberated per nerve volley. The paralysis is evidently not due to defective synthesis of acetylcholine because acetylcholine is liberated in control and high-potassium perfusates, the choline acetylase activity and the acetylcholine content of lumbar ventral roots and peroneal nerves do not differ from that in normal dogs, and the tick-paralyzed muscle differs from that in the hemicholinium-treated animal in its response to a train of nerve pulses after previous tetanization. As somatic motor nerve fibers in the paralyzed dog have previously been shown to conduct a nerve impulse and the factors required for acetylcholine release at the nerve terminal apparently are not absent in the paralyzed animal, the mechanism of the paralysis is probably due to an inability of the nerve impulse to traverse the terminal presynaptic fibers. The 'lesion' evidently extends to the end of the presynaptic fiber, i.e. more distally than in botulism, because direct stimulation of the tick-paralyzed muscle fails to liberate acetylcholine.

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