Postnatal increase of unmyelinated axon profiles in the feline ventral root L7

1981 ◽  
Vol 201 (3) ◽  
pp. 343-351 ◽  
Author(s):  
Mårten Risling ◽  
Claes Hildebrand ◽  
Håkan Aldskogius
Keyword(s):  
Ventral Root ◽  
Unmyelinated Axon

scholarly journals Commissural Interneurons in Rhythm Generation and Intersegmental Coupling in the Lamprey Spinal Cord

1999 ◽  
Vol 81 (5) ◽  
pp. 2037-2045 ◽  
Author(s):  
James T. Buchanan
Keyword(s):  
Spinal Cord ◽  
Amino Acid ◽  
Excitatory Amino Acid ◽  
Rhythmic Activity ◽  
Ventral Root ◽  
Rhythm Generation ◽  
Spinal Segment ◽  
Spinal Segments ◽  
Autocorrelation Method

Commissural interneurons in rhythm generation and intersegmental coupling in the lamprey spinal cord. To test the necessity of spinal commissural interneurons in the generation of the swim rhythm in lamprey, longitudinal midline cuts of the isolated spinal cord preparation were made. Fictive swimming was then induced by bath perfusion with an excitatory amino acid while recording ventral root activity. When the spinal cord preparation was cut completely along the midline into two lateral hemicords, the rhythmic activity of fictive swimming was lost, usually replaced with continuous ventral root spiking. The loss of the fictive swim rhythm was not due to nonspecific damage produced by the cut because rhythmic activity was present in split regions of spinal cord when the split region was still attached to intact cord. The quality of this persistent rhythmic activity, quantified with an autocorrelation method, declined with the distance of the split spinal segment from the remaining intact spinal cord. The deterioration of the rhythm was characterized by a lengthening of burst durations and a shortening of the interburst silent phases. This pattern of deterioration suggests a loss of rhythmic inhibitory inputs. The same pattern of rhythm deterioration was seen in preparations with the rostral end of the spinal cord cut compared with those with the caudal end cut. The results of this study indicate that commissural interneurons are necessary for the generation of the swimming rhythm in the lamprey spinal cord, and the characteristic loss of the silent interburst phases of the swimming rhythm is consistent with a loss of inhibitory commissural interneurons. The results also suggest that both descending and ascending commissural interneurons are important in the generation of the swimming rhythm. The swim rhythm that persists in the split cord while still attached to an intact portion of spinal cord is thus imposed by interneurons projecting from the intact region of cord into the split region. These projections are functionally short because rhythmic activity was lost within approximately five spinal segments from the intact region of spinal cord.

A study of the axon initial segment and proximal axon of neurons in the primate motor and somatic sensory cortices

1979 ◽  
Vol 285 (1006) ◽  
pp. 173-197 ◽  
Keyword(s):  
Initial Segment ◽  
Pyramidal Cells ◽  
Stellate Cells ◽  
Myelinated Axon ◽  
Full Length ◽  
Unmyelinated Axon ◽  
Parent Cell ◽  
Axon Terminals ◽  
Sensory Cortices ◽  
Axon Initial Segments

The axon initial segments of pyramidal cells and large and small stellate cells in the primate sensori-motor cortex have a typical membrane undercoating and bundles of neurotubules. Those of pyramidal cells are directed towards the white matter whereas those of large and small stellate cells often run obliquely or towards the cortical surface and may be curved. Cisternal organs in these initial segments are related to symmetrical axon terminals, frequently coming into close apposition to the non-synaptic part of these terminals adjacent to the synapse between the axon terminal and initial segment. The dense plates of cisternal organs and the membrane undercoating of the initial segment are specifically stained by ethanolic phosphotungstic acid (ethanolic PTA). Pyramidal initial segments have spines which receive only symmetrical synapses, as do the shafts of the initial segments of each cell type. The full length of the initial segment was studied for fourteen pyramidal and two large stellate cells. All gave rise to myelinated axons although two pyramidal cells had lengths of unmyelinated axon between the initial segment and myelinated axon. One of these lengths of unmyelinated axon made an asymmetric synapse on to a dendrite just after losing its initial segment features. Quantitative analysis of these complete initial segments showed that whereas the diameter of the initial segment and the axon it gave rise to were approximately proportional to the size of the parent cell soma over a considerable range of cell diameters, the length of the initial segment appeared to be unrelated to either its diameter or the size of its parent soma but varied between 30 and 55 μm apparently at random. Synapses were evenly distributed along the full length of the complete pyramidal initial segments, but the density of synapses on the initial segments of supragranular pyramids was about three times that on those of infragranular pyramids and cisternal organs were similarly more frequent in the initial segments of supragranular pyramids.

scholarly journals Modulation of the visceromotor reflex by a lumbosacral ventral root avulsion injury and repair in rats

2012 ◽  
Vol 303 (5) ◽  
pp. F641-F647 ◽  
Author(s):  
Huiyi H. Chang ◽  
Leif A. Havton
Keyword(s):  
Cauda Equina ◽  
Experimental Models ◽  
Ventral Root ◽  
Oblique Muscle ◽  
Emg Activity ◽  
Noxious Stimulation ◽  
Electromyographic Activity ◽  
Root Avulsion ◽  
Contraction Duration ◽  
Ventral Root Avulsion

Increased abdominal muscle wall activity may be part of a visceromotor reflex (VMR) response to noxious stimulation of the bladder. However, information is sparse regarding the effects of cauda equina injuries on the VMR in experimental models. We studied the effects of a unilateral L6-S1 ventral root avulsion (VRA) injury and acute ventral root reimplantation (VRI) into the spinal cord on micturition reflexes and electromyographic activity of the abdominal wall in rats. Cystometrogram (CMG) and electromyography (EMG) of the abdominal external oblique muscle (EOM) were performed. All rats demonstrated EMG activity of the EOM associated with reflex bladder contractions. At 1 wk after VRA and VRI, the duration of the EOM EMG activity associated with reflex voiding was significantly prolonged compared with age-matched sham rats. However, at 3 wk postoperatively, the duration of the EOM responses remained increased in the VRA series but had normalized in the VRI group. The EOM EMG duration was normalized for both VRA and VRI groups at 8–12 wk postoperatively. CMG recordings show increased contraction duration at 1 and 3 wk postoperatively for the VRA series, whereas the contraction duration was only increased at 1 wk postoperatively for the VRI series. Our studies suggest that a unilateral lumbosacral VRA injury results in a prolonged VMR to bladder filling using a physiological saline solution. An acute root replantation decreased the VMR induced by VRA injury and provides earlier sensory recovery.

Defecation Induced by Stimulation of Sacral S2 Spinal Root in Cats

2021 ◽  
Author(s):  
Jicheng Wang ◽  
Zhijun Shen ◽  
Bing Shen ◽  
Jianan Jian ◽  
Travis Hannan ◽  
...  
Keyword(s):  
Distal Colon ◽  
Spinal Nerve ◽  
Ventral Root ◽  
Spinal Root ◽  
Balloon Catheters ◽  
Minimally Invasive Surgical ◽  
Lead Electrode ◽  
Cord Injury ◽  
Minute Duration ◽  
Stimulation Of

The aim of this study was to determine if stimulation of sacral spinal nerve roots can induce defecation in cats. In anesthetized cats, bipolar hook electrodes were placed on the S1-S3 dorsal and/or ventral roots. Stimulus pulses (1-50 Hz, 0.2 ms) were applied to an individual S1-S3 root to induce proximal/distal colon contractions and defecation. Balloon catheters were inserted into the proximal and distal colon to measure contraction pressure. Glass marbles were inserted into the rectum to demonstrate defecation by videotaping the elimination of marbles. Stimulation of the S2 ventral root at 7 Hz induced significantly (p<0.05) larger contractions (32±9 cmH2O) in both proximal and distal colon than stimulation of the S1 or S3 ventral root. Intermittent (5 times) stimulation (1 minute on and 1 minute off) of both dorsal and ventral S2 roots at 7 Hz produced reproducible colon contractions without fatigue, while continuous stimulation of 5-minute duration caused significant fatigue in colon contractions. Stimulation (7 Hz) of both dorsal and ventral S2 roots together successfully induced defecation that eliminated 1-2 marbles from the rectum. This study indicates the possibility to develop a novel neuromodulation device to restore defecation function after spinal cord injury using a minimally invasive surgical approach to insert a lead electrode via the sacral foramen to stimulate a sacral spinal root.

Activity and motor unit size in partially denervated rat medial gastrocnemius

1994 ◽  
Vol 76 (6) ◽  
pp. 2663-2671 ◽  
Author(s):  
L. J. Einsiedel ◽  
A. R. Luff
Keyword(s):  
Motor Unit ◽  
Gastrocnemius Muscle ◽  
Motor Units ◽  
Ventral Root ◽  
Treadmill Walking ◽  
Medial Gastrocnemius ◽  
Unit Size ◽  
Partial Denervation ◽  
Motoneuron Activity ◽  
Medial Gastrocnemius Muscle

The aim of the study was to determine whether increased motoneuron activity induced by treadmill walking would alter the extent of motoneuron sprouting in the partially denervated rat medial gastrocnemius muscle. An extensive partial denervation was effected by unilateral section of the L5 ventral root, and it is very likely that all units remaining in the medial gastrocnemius were used in treadmill walking. Rats were trained for 1.5 h/day and after 14 days were walking at least 1 km/day. Motor unit characteristics were determined 24 days after the partial denervation and were compared with units from partially denervated control (PDC) animals and with units from normal (control) animals. In PDC rats, force developed by slow, fast fatigue-resistant, and fast intermediate-fatigable motor units increased substantially compared with control animals; that of fast-fatigable units did not increase. In partially denervated exercised animals, force developed by slow and fast-fatigue-resistant units showed no further increase, but fast-intermediate- and fast-fatigable units showed significant increases compared with those in PDC animals. The changes in force were closely paralleled by changes in innervation ratios. We concluded that neuronal activity is an important factor in determining the rate of motoneuron sprouting.

Motoneuron properties during motor inhibition produced by microinjection of carbachol into the pontine reticular formation of the decerebrate cat

1987 ◽  
Vol 57 (4) ◽  
pp. 1118-1129 ◽  
Author(s):  
F. R. Morales ◽  
J. K. Engelhardt ◽  
P. J. Soja ◽  
A. E. Pereda ◽  
M. H. Chase
Keyword(s):  
Spinal Cord ◽  
Motor Activity ◽  
Reticular Formation ◽  
Input Resistance ◽  
Ventral Root ◽  
Monosynaptic Reflex ◽  
Pontine Reticular Formation ◽  
Active Sleep ◽  
Decerebrate Cat ◽  
Inhibitory Postsynaptic Potentials

It is well established that cholinergic agonists, when injected into the pontine reticular formation in cats, produce a generalized suppression of motor activity (1, 3, 6, 14, 18, 27, 33, 50). The responsible neuronal mechanisms were explored by measuring ventral root activity, the amplitude of the Ia-monosynaptic reflex, and the basic electrophysiological properties of hindlimb motoneurons before and after carbachol was microinjected into the pontine reticular formation of decerebrate cats. Intrapontine microinjections of carbachol (0.25-1.0 microliter, 16 mg/ml) resulted in the tonic suppression of ventral root activity and a decrease in the amplitude of the Ia-monosynaptic reflex. An analysis of intracellular records from lumbar motoneurons during the suppression of motor activity induced by carbachol revealed a considerable decrease in input resistance and membrane time constant as well as a reduction in motoneuron excitability, as evidenced by a nearly twofold increase in rheobase. Discrete inhibitory postsynaptic potentials were also observed following carbachol administration. The changes in motoneuron properties (rheobase, input resistance, and membrane time constant), as well as the development of discrete inhibitory postsynaptic potentials, indicate that spinal cord motoneurons were postsynaptically inhibited following the pontine administration of carbachol. In addition, the inhibitory processes that arose after carbachol administration in the decerebrate cat were remarkably similar to those that are present during active sleep in the chronic cat. These findings suggest that the microinjection of carbachol into the pontine reticular formation activates the same brain stem-spinal cord system that is responsible for the postsynaptic inhibition of alpha-motoneurons that occurs during active sleep.

scholarly journals Effects of Baclofen on Spinal Reflexes and Persistent Inward Currents in Motoneurons of Chronic Spinal Rats With Spasticity

2004 ◽  
Vol 92 (5) ◽  
pp. 2694-2703 ◽  
Author(s):  
Y. Li ◽  
X. Li ◽  
P. J. Harvey ◽  
D. J. Bennett
Keyword(s):  
Spinal Cord ◽  
Ventral Root ◽  
Spinal Reflexes ◽  
Monosynaptic Reflex ◽  
Persistent Inward Currents ◽  
Inward Currents ◽  
Muscle Spasms ◽  
Acute Spinal Rats ◽  
Chronic Spinal Rats ◽  
Higher Doses

In the months after spinal cord injury, motoneurons develop large voltage-dependent persistent inward currents (PICs) that cause sustained reflexes and associated muscle spasms. These muscle spasms are triggered by any excitatory postsynaptic potential (EPSP) that is long enough to activate the PICs, which take >100 ms to activate. The PICs are composed of a persistent sodium current (Na PIC) and a persistent calcium current (Ca PIC). Considering that Ca PICs have been shown in other neurons to be inhibited by baclofen, we tested whether part of the antispastic action of baclofen was to reduce the motoneuron PICs as opposed to EPSPs. The whole sacrocaudal spinal cord from acute spinal rats and spastic chronic spinal rats (with sacral spinal transection 2 mo previously) was studied in vitro. Ventral root reflexes were recorded in response to dorsal root stimulation. Intracellular recordings were made from motoneurons, and slow voltage ramps were used to measure PICs. Chronic spinal rats exhibited large monosynaptic and long-lasting polysynaptic ventral root reflexes, and motoneurons had associated large EPSPs and PICs. Baclofen inhibited these reflexes at very low doses with a 50% inhibition (EC50) of the mono- and polysynaptic reflexes at 0.26 ± 0.07and 0.25 ± 0.09 (SD) μM, respectively. Baclofen inhibited the monosynaptic reflex in acute spinal rats at even lower doses (EC50 = 0.18 ± 0.02 μM). In chronic (and acute) spinal rats, all reflexes and EPSPs were eliminated with 1 μM baclofen with little change in motoneuron properties (PICs, input resistance, etc), suggesting that baclofen's antispastic action is presynaptic to the motoneuron. Unexpectedly, in chronic spinal rats higher doses of baclofen (20–30 μM) significantly increased the total motoneuron PIC by 31.6 ± 12.4%. However, the Ca PIC component (measured in TTX to block the Na PIC) was significantly reduced by baclofen. Thus baclofen increased the Na PIC and decreased the Ca PIC with a net increase in total PIC. By contrast, when a PIC was induced by 5-HT (10–30 μM) in motoneurons of acute spinal rats, baclofen (20–30 μM) significantly decreased the PIC by 38.8 ± 25.8%, primarily due to a reduction in the Ca PIC (measured in TTX), which dominated the total PIC in these acute spinal neurons. In summary, baclofen does not exert its antispastic action postsynaptically at clinically achievable doses (<1 μM), and at higher doses (10–30 μM), baclofen unexpectedly increases motoneuron excitability (Na PIC) in chronic spinal rats.

ATP concentrations and muscle tension increase linearly with muscle contraction

2003 ◽  
Vol 95 (2) ◽  
pp. 577-583 ◽  
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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