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At least 1,531 records · Page 85Linked to original sources
PubMed2000

A controlled study on the effects of transcutaneous electrical nerve stimulation and interferential therapy upon the RIII nociceptive and H-reflexes in humans.

OBJECTIVE: To study the effect of transcutaneous electrical nerve stimulation (TENS) and interferential therapy (IFT) upon the RIII nociceptive reflex and H-reflex. DESIGN: Double-blind conditions. PARTICIPANTS: Seventy healthy subjects were randomly allocated to one of seven groups (n = 10 per group): Control, TENS 1 (5 Hz), TENS 2 (100 Hz), TENS 3 (200 Hz), IFT 1 (5 Hz), IFT 2 (100 Hz), IFT 3 (200 Hz). INTERVENTION: In the treatment groups, stimulation was applied over the right sural nerve for 15 minutes. MAIN OUTCOME MEASURES: Ipsilateral RIII and H-reflexes were recorded before treatment, immediately after treatment, and subsequently at 25, 35, and 45 minutes. Subjects rated the pain associated with the RIII reflex using a computerized visual analogue scale (VAS). RESULTS: Statistical analysis using ANOVA showed no significant differences between baseline and posttreatment measurement for RIII reflex, H-reflex, or VAS data. CONCLUSION: These results suggest that neither type of electrical stimulation (TENS or IFT) affects the RIII or H-reflexes, at least using the parameters and application time in this study.

Adolescent↗
PubMed2006

Restoration of frequency-dependent depression of the H-reflex by passive exercise in spinal rats.

STUDY DESIGN: Hyper-reflexia, measured as a decrease of low frequency-dependent depression of the H-reflex, is known to occur in both humans and animals after spinal cord injury (SCI). Previous studies have shown that passive exercise for 3 months could be used to restore low frequency-dependent depression of the H-reflex after SCI. OBJECTIVE: To determine the effects of various periods of time on the ability of passive exercise to restore low frequency-dependent depression of the H-reflex. SETTING: Spinal Cord Injury Mobilization Program of the Center for Translational Neuroscience, the research arm of the Jackson T Stephens Spine and Neuroscience Institute, Little Rock, AR, USA. METHODS: Adult rats underwent complete spinal cord transection at the T10 level. The hindlimbs were passively exercised in different groups of rats for 1 h/day, 5 days/week for 15, 30, 45, 60, or 90 days, and low frequency-dependent depression of the H-reflex was tested. RESULTS: Statistically significant low frequency-dependent depression of the H-reflex was evident by 30 days of exercise, although numerical reductions were seen even at 15 days. There was a linear decrease in low frequency-dependent depression of the H-reflex with duration of passive exercise. CONCLUSIONS: Passive exercise can restore frequency-dependent depression of spinal reflexes in a time-dependent manner if used following complete spinal transection.

Animals↗
PubMed2004

Stretch reflex excitability of the anti-gravity ankle extensor muscle in elderly humans.

AIM: To examine whether the stretch reflex excitability of the soleus muscle changes with age, stretch reflexes at rest (REST) and during weak voluntary contractions (ACT) were elicited in 18 older and 14 younger subjects. METHOD: The amplitude of the stretch reflex responses and gain, defined as the gradient of the regression line for the relation between stretch reflex responses against the angular velocity of the applied perturbation, were evaluated in each short-latency (M1) and two long-latency components (M2 and M3). RESULTS: It was found that in the older group, both the amplitude and gain of the M1 component did not change from the REST to the ACT conditions, whereas in the younger group both variables significantly increased from the REST to ACT conditions. The latency of the M1 component was significantly shorter under the REST condition (older vs. younger: 51.8 +/- 7.37 vs. 55.1 +/- 8.69 ms), while no group differences were found in those variables under the ACT condition, suggesting that the muscle-tendon complexes of SOL muscles of the older subjects were less elastic and had less slack, probably due to age-related histochemical alterations. Further, the Hoffman reflex (H-reflex), elicited during the REST condition in 10 older and 11 younger subjects showed no significant differences, suggesting that the soleus motoneuron response to the Ia input was comparable between the two subject groups. CONCLUSION: The histochemical alterations occurring with the ageing process might augment the short-latency stretch reflex in the SOL muscle without enhancement of motoneuronal excitability, and this effect might be masked when the muscle is voluntarily activated.

Adult↗
PubMed1959

Functional organization in the terminal segments of the spinal cord with a consideration of central excitatory and inhibitory latencies in monosynaptic reflex systems.

Prominent monosynaptic and disynaptic reflex discharges characterize ipsilateral reflex transmission in the third sacral segment. Convergence upon the motoneurons from the two sides of the body is inhibitory, that through disynaptic paths excitatory. The relative latencies of excitation and inhibition of reflex responses, of excitatory and inhibitory synaptic potentials, and of various aspects of impulse discharge in motoneurons are considered. It is concluded: (1) that a direct (i.e. monosynaptic) action of primary afferent collaterals upon motoneurons is responsible for inhibition of monosynaptic reflex discharge of antagonist motoneurons within a myotatic unit; (2) that the inhibitory postsynaptic potential as described is not the primary agency for monosynaptic reflex inhibition of monosynaptic reflex discharge; (3) that, however, a common causal agent may be responsible for inhibition of reflex discharge and for generation of an inhibitory postsynaptic potential; and (4) that the inhibitory post-synaptic potential may be linked with, or be the agent for, inhibition of soma response.

Motor Neurons↗
PubMed1987

Stretch and vibration reflexes of wrist flexor muscles in spasticity.

The surface electromyographic (EMG) reflex responses of the voluntarily contracting flexor carpi radialis evoked by 'stretch' and by tendon vibration have been compared in patients with spasticity of the upper limb, arising from upper motor neuron lesions, and normal subjects. Reflex responses to 'stretch' comprised increases in EMG activity lasting up to 100 ms which were often divided into 'short' and 'long'-latency peaks. The short-latency responses of spastic patients were increased in size compared with those of normal subjects whereas later activity was commonly reduced or absent. In both groups vibration elicited short-latency, essentially phasic responses with activity falling back to or below the background level within 50 ms despite continuing stimulation. These initial reflex responses were exaggerated in the spastics as compared with the normals. In the relaxed state 'stretch' and vibration either failed to elicit reflex responses in normal subjects or reflexes were of small amplitude; in spastic patients both modes of stimulation regularly evoked well developed responses. These findings with 'stretch' and vibration, both of which forms of stimulation powerfully excite primary endings of muscle spindles, support the view that group Ia afferent-mediated reflex action is enhanced in spasticity. The observation that the normal long-latency responses evoked by stretch, which have been attributed to the action of spindle group II afferents (Matthews, 1984a) additionally excited with this stimulus, are depressed in many spastic patients is consistent with reduced group II effects. Observed abnormalities of stretch reflex behaviour did not readily explain the severity of accompanying spasticity of individual patients.

Adult↗
PubMed1982

Age-related changes in monosynaptic reflex excitability.

The excitability of the H-reflex was tested in a younger group (19 to 31 years) and an older group (60 to 72 years) of subjects. The threshold for the H-reflex was higher and the reflex latency was 7 msec longer in the older group of subjects. Also, the H-reflex amplitude was significantly smaller, longer in duration and polyphasic in shape whereas the time delay between the M-response and the H-reflex (central latency) was 5 msec longer in the older group. The H-reflex recovery curves of the older subjects demonstrated a longer primary inhibition period (94 msec in older subjects, 44 msec in younger subjects) and was slower, more inhibited, and took a longer time for maximal recovery. In accordance with previous findings, these results are attributed to possible central as well as peripheral and muscle fiber defects in old subjects. Such changes must be taken into account when using H-reflex tests in the clinic.

Aged↗
PubMed1995

Nitrous oxide depresses the H-reflex in children with cerebral palsy.

Hoffmann's reflex or H-reflex (HR) is an electrically elicited reflex that measures excitability of motoneurons and shares some physiologic properties with the deep tendon reflex. Children with tendon hyperreflexia due to cerebral palsy usually have higher amplitude HRs. Nitrous oxide (N2O) depresses the HR in patients with normal spinal reflexes, although the effect of N2O in conditions with hyperreflexia such as cerebral palsy is not known. We propose to determine the effect of N2O on the amplitude of the HR under general anesthesia in children with hyperreflexia due to cerebral palsy. We studied eight children undergoing selective dorsal rhizotomy (SDR) for the relief of spasticity. The maximum amplitudes of the HR (HRmax) and direct motor response (MRmax) were routinely evoked under the following anesthetic conditions: 1) sufentanil and 66% N2O/33% oxygen; and 2) sufentanil and 100% oxygen. The HRmax amplitude was significantly lower when N2O was part of the inspired gas mixture. The differences between the no N2O and the 66% N2O groups were significant. The MRmax did not change significantly. Abnormal spinal reflexes seen in spastic diplegia can be abolished by inhaled N2O. This finding also suggests that N2O-induced depression of spinal reflexes should be a consideration during physiologic monitoring of the spinal cord under general anesthesia.

Cerebral Palsy↗
PubMed1987

Changes of electrically elicited reflexes in hand and forearm muscles in man.

Cutaneo-muscular reflexes with short and long latency excitatory phases following digital nerve stimulation were observed in the first dorsal interosseus muscle of the hand in healthy subjects. The short latency reflex was obtained also with the H-reflex method in the flexor carpi radialis muscle, stimulating the median nerve, with a mean latency (+/- SE) of 15.4 +/- 0.5 ms. The height of the subject correlated with the H-reflex latency. The amplitudes of maximal M-response and maximal H-reflex were higher in athletes than in normals. During weak voluntary contraction of the muscle studied the 50% H-reflex amplitude increased and during passive stretching of wrist flexors the resting amplitude of the 50% H-reflex decreased.

Adult↗
PubMed1996

Sacral cord conduction time of the soleus H-reflex.

The sacral cord conduction time of the soleus H-reflex was investigated in 30 normal adult subjects using three different methods. (1) The posterior tibial nerve was stimulated at the popliteal fossa by graded electric shocks, and the recordings were made from different lumbar epidural intervertebral levels. The afferent action potentials from the dorsal roots and the reflexively evoked efferent action potentials from the ventral roots were recorded. The time interval between the negative peaks of the ventral and dorsal root potentials was used to calculate the approximate sacral cord reflex delay time, which was found to be 1.3 ms. on average. (2) The sacral cord reflex delay time was found to be about 2.0 ms using the conduction time of the afferent, that of the efferent limbs and total reflex time of the soleus H-response. (3) By stimulating the lumbosacral roots at the epidural levels and using the difference between the soleus H and M response latencies, the sacral cord reflex delay was determined to be approximately 2.4 ms. These findings indicated that the soleus H-reflex is exclusively monosynaptic. It is proposed that in humans the synaptic transmission at the sacral cord is approximately 0.4 ms.

Adult↗
PubMed1989

The oculocardiac reflex in blepharoplasty surgery.

The oculocardiac reflex (OCR), a previously undescribed phenomenon in aesthetic blepharoplasty surgery, involves intraoperative bradycardia exceeding 10 percent of the preoperative heart rate or any dysrhythmia during ocular manipulation. It is a trigeminal-vagal-mediated reflex arc. The oculocardiac reflex was noted to occur in 25 of 100 patients (25 percent) undergoing blepharoplasty. A data sheet designed and distributed for use in the operating room identified a reflex-prone patient (RPP) as a young, anxious female, with a cardiac history, operated on under light anesthesia with aggressive fat pad resection. The oculocardiac reflex was more likely to occur in a reflex-prone patient during traction on the medial fat pads and in the left eye. Despite anticipating the fatigue phenomenon in those patients who exhibited a profound bradycardia (35 to 40 beats per minute), it was necessary to release traction in order to permit the heart rate to return to normal. Awareness and treatment of this potentially life-threatening oculocardiac reflex are necessary. Careful patient surveillance and monitoring are mandatory.

Adult↗
PubMedDate not supplied

Ablation of cerebellar nuclei prevents H-reflex down-conditioning in rats.

While studies of cerebellar involvement in learning and memory have described plasticity within the cerebellum, its role in acquisition of plasticity elsewhere in the CNS is largely unexplored. This study set out to determine whether the cerebellum is needed for acquisition of the spinal cord plasticity that underlies operantly conditioned decrease in the H-reflex, the electrical analog of the spinal stretch reflex. Rats in which the cerebellar output nuclei dentate and interpositus (DIN) had been ablated were exposed for 50 d to the H-reflex down-conditioning protocol. DIN ablation, which in itself had no significant long-term effect on H-reflex size, entirely prevented acquisition of a smaller H-reflex. Since previous studies show that corticospinal tract (CST) transection also prevents down-conditioning while transection of the rubrospinal tract and other major descending tracts does not, this result implies that DIN output that affects cortex is essential for generation of the CST activity that induces the spinal cord plasticity, which is, in turn, directly responsible for the smaller H-reflex. The result extends the role of the cerebellum in learning and memory to include participation in induction of plasticity elsewhere in the CNS, specifically in the spinal cord. The cerebellum might simply support processes in sensorimotor cortex or elsewhere that change the spinal cord, or the cerebellum itself might undergo plasticity similar to that occurring with vestibulo-ocular reflex (VOR) or eyeblink conditioning.

Animals↗
PubMed1987

Stapedius reflex and cerebellopontine angle tumours.

The stapedius reflex was investigated in 61 patients with cerebellopontine angle tumours, in order to evaluate the reliability of the reflex-decay test in VIIIth nerve disorders. The reflex was completely normal in 11% of the patients. The 2 most frequently observed abnormalities were (1) an absence of the reflex when stimulating the ear on the side of the tumour, and (2) the conjunction of pathological reflex-decay at 0.5 kHz with a unilateral threshold elevation and/or absence of the reflex at other frequencies. The decay test was normal in one-third of the patients with a preserved reflex.

Acoustic Impedance Tests↗
PubMed1983

Time course of segmental reflex changes after chronic spinal cord hemisection in the rat.

In a companion paper (Hultborn & Malmsten 1983 a) it was described that, in the cat, direct excitatory reflexes became larger on the side of a chronic spinal hemisection than on the other side. In this paper the time course for change of the size of excitatory reflexes after spinal cord hemisection in the rat is described. Ipsilateral reflexes obtained by stimulation of cut dorsal roots L 4 and L 5 were recorded in the corresponding cut ventral roots. It was found that reflexes became larger on the lesioned (left) side than on the opposite side. For both mono- and polysynaptic reflexes there was a marked peak in left/right ratio on reflex size at 2 to 6 days post lesion. The ratio then returned to normal but increased again from about 21 days until at least 135 days. In control rats reflexes were larger on the right side, in agreement with findings in the cat.

Afferent Pathways↗
PubMed1986

Fusimotor reflexes in triceps surae muscle elicited by stretch of muscles in the contralateral hind limb of the cat.

Experiments were performed on twenty-one cats anaesthetized with alpha-chloralose. The aim of this study was to investigate the reflex effects on triceps surae and plantaris fusimotor neurones elicited by tonic stretch of the contralateral posterior biceps and semitendinosus (p.b.s.t.) and the contralateral triceps surae and plantaris muscles, to compare these effects with the effects evoked by flexion or extension of the intact contralateral hind limb (Appelberg, Hulliger, Johansson & Sojka, 1984) and to clarify the interactions between the reflexes from contralateral and ipsilateral muscles. Activity in fusimotor neurones was studied indirectly by recording from primary muscle spindle afferents of the triceps surae and plantaris muscle. The mean rate of firing and the modulation of the afferent response to sinusoidal extension of the triceps surae and plantaris muscles was determined. Control measurements were made with the ipsilateral p.b.s.t., the contralateral p.b.s.t. and the contralateral triceps and plantaris muscles relaxed. Tests were made with tonic stretch of one of these muscles alone or with two of them simultaneously. With stretch of the contralateral p.b.s.t. ten out of eighty-four primary afferents (11.9%) showed predominantly dynamic reflexes (six out of forty-one in spinalized preparations: 14.6%), twenty-two (26.2%) showed mixed or predominantly static effects (one spinalized: 2.4%) and fifty-two units (61.9%) showed no effect (thirty-four spinalized: 83.0%). The reflex effects could be reproduced by electrical stimulation of the cut contralateral p.b.s.t. nerve either at group II or at group III strength. With stretch of the contralateral triceps and plantaris muscles seventy out of seventy-six (92.1%) primary muscle spindle afferents showed no effect and six (7.9%) mixed or predominantly static reflex effects. In general, the reflex effects were not accompanied by detectable electromyographic (e.m.g.) activity in the ipsilateral triceps and plantaris (recorded with surface or needle electrodes), indicating that the reflexes mainly involved gamma-motoneurones. The difference in efficacy between contralateral flexor (p.b.s.t.) and extensor (triceps and plantaris) muscles seems to be in accordance with the response pattern found with extension or flexion of the intact contralateral hind limb (Appelberg et al. 1984).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1999

Reduced reflex sensitivity persists several days after long-lasting stretch-shortening cycle exercise.

The mechanisms related to the acute and delayed secondary impairment of the stretch reflex function were investigated after long-lasting stretch-shortening cycle exercise. The results demonstrated a clear deterioration in muscle function immediately after fatigue, which was accompanied by a clear reduction in active and passive reflex sensitivity. For active and passive stretch reflexes, this reduction was biphasic (P < 0.05 to P < 0.001). However, for the ratio of the electrically induced maximal Hoffmann reflex to the maximal mass compound action potential, only one significant reduction was seen immediately after fatigue (71.2%, P < 0.01). A similar significant (P < 0.01) decrease in the stretch-resisting force of the muscle was also detected. Clear increases were found in the indirect markers of muscle damage (serum creatine kinese activity and skeletal troponin I), which could imply the occurrence of ultrastructural muscle damage. It is suggested that the acute reduction in reflex sensitivity is of reflex origin and due to two active mechanisms, disfacilitation and presynaptic inhibition. However, the delayed second decline in the sensitivity of some reflex parameters may be attributable to the secondary injury, because of some inflammatory response to the muscle damage. This might emphasize the role of presynaptic inhibition via group III and IV muscle afferents.

Adult↗
PubMed2004

Reorganization of reflex responses mediated by different afferent sensory fibers after spinal cord transection.

Adult rats were submitted to a complete spinal cord transection at T9 level to address peripheral and spinal reflex changes in the caudal lumbar segments. Compound muscle and nerve action potentials decreased in amplitude and increased their duration between 14 and 30 days but recovered to near to normal values thereafter. The H wave amplitude increased during follow-up, resulting in significantly higher H/M ratio in tibialis anterior (223%), gastrocnemius (160%), and plantar (304%) muscles with respect to preoperatory values (P < 0.01). Sixty minutes after spinal cord transection, component C1 (conveyed by Aalphabeta afferents) disappeared in the crossed but not in the ipsilateral withdrawal reflex. Components C2 (Adelta) and C3 (C afferents) were abolished on both. C1 and C3 reappeared for both reflexes in all injured animals, while C2 reappeared in a few cases. C1 ipsilateral component became highly facilitated (209% of presurgery values, P < 0.01), whereas C3 (82%) and C2 (24%) recovered partially. Crossed reflex component C1 attained in all animals similar to normal values (85%) but with longer duration. C3 increased with time although it remained significantly lower than the original (67%) whereas C2 reappeared in only 2/8 animals. In conclusion, spinal cord injury induces a transient disability of caudal spinal cord segments that progressively reverts along time. Ipsilateral reflex components mediated by thick Aalphabeta fibers (H reflex and C1) but not those mediated by thin fibers (C2 and C3) remained present after injury showing long-lasting facilitation whereas contralateral reflex components were abolished after injury and showed limited recovery.

Afferent Pathways↗
PubMed2004

Conversion of the modulatory actions of dopamine on spinal reflexes from depression to facilitation in D3 receptor knock-out mice.

Descending monoaminergic systems modulate spinal cord function, yet spinal dopaminergic actions are poorly understood. Using the in vitro lumbar cord, we studied the effects of dopamine and D2-like receptor ligands on spinal reflexes in wild-type (WT) and D3-receptor knock-out mice (D3KO). Low dopamine levels (1 microM) decreased the monosynaptic "stretch" reflex (MSR) amplitude in WT animals and increased it in D3KO animals. Higher dopamine concentrations (10-100 microM) decreased MSR amplitudes in both groups, but always more strongly in WT. Like low dopamine, the D3 receptor agonists pergolide and PD 128907 reduced MSR amplitude in WT but not D3KO mice. Conversely, D3 receptor antagonists (GR 103691 and nafadotride) increased the MSR in WT but not in D3KO mice. In comparison, D2-preferring agonists bromocriptine and quinpirole depressed the MSR in both groups. Low dopamine (1-5 microM) also depressed longer-latency (presumably polysynaptic) reflexes in WT but facilitated responses in D3KO mice. Additionally, in some experiments (e.g., during 10 microM dopamine or pergolide in WT), polysynaptic reflexes were facilitated in parallel to MSR depression, demonstrating differential modulatory control of these reflex circuits. Thus, low dopamine activates D3 receptors to limit reflex excitability. Moreover, in D3 ligand-insensitive mice, excitatory actions are unmasked, functionally converting the modulatory action of dopamine from depression to facilitation. Restless legs syndrome (RLS) is a CNS disorder involving abnormal limb sensations. Because RLS symptoms peak at night when dopamine levels are lowest, are relieved by D3 agonists, and likely involve increased reflex excitability, the D3KO mouse putatively explains how impaired D3 activity could contribute to this sleep disorder.

Animals↗
PubMed1986

Spinal reflexes in chinoform-administered rats.

We examined the effects of chinoform (CF) on the spinal reflexes and the descending influences on the spinal reflexes from the locus coeruleus (LC) and the nucleus raphe magnus (NRM) in rats. The spinal reflex potential was recorded from the L5 ventral root following stimulation of the L5 dorsal root, and the effects of electrical stimulation of the LC and the NRM were tested in anesthetized rats. CF was suspended in Tween 80 and administered for two days (400 mg/kg, i. p./day) before the measurement of the spinal reflexes. In all rats treated with CF, death or motor incoordinations such as abnormal gait and hindlimb ataxia were observed. However, the control and CF-treated groups are not different in the amplitude and shape of the reflexes and in the influences of the LC and the NRM on the reflexes from the LC and the NRM. These results suggest that segmental spinal reflexes and descending influences from the LC and the NRM are not affected in rats suffered from motor incoordination by acute CF.

Animals↗