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At least 973 records · Page 54Linked to original sources
PubMed1982

[Detection of peripheral diabetic neuropathy. A reappraisal of electrophysiological data].

In addition to motor and sensory nerve conduction, monosynaptic triceps surae reflex, amplitude of median nerve voltage and response of extensor digitorum brevis and soleus muscles were investigated in 29 diabetic patients. These parameters were altered earlier than motor and sensory nerve conduction, which considerably increased the incidence of subclinical peripheral neuropathy (90% of the patients). It was also found that sensory fibers were affected earlier than motor fibers. The electrically detected neuropathy correlated with duration of diabetes and control of glycaemia.

Axons↗
PubMed1992

Presynaptic dopaminergic inhibition of the spinal reflex in rats.

Dopaminergic influence on spinal monosynaptic transmission was examined in rats. Monosynaptic mass reflex (MMR) was recorded from the ventral root L6 following supramaximal stimulation (0.2 Hz; 0.1 ms) to the ipsilateral dorsal root L6 in spinalized rat under pentobarbitone sodium (40 mg/kg, i.p.) anaesthesia. MMR was inhibited by intravenous administration of the dopaminergic agonist, apomorphine (50-200 ug/kg) in a dose-dependent manner. The attenuatory effect of apomorphine (200 ug/kg i.v.) on the reflex could be reversed by the dopaminergic antagonist haloperidol (0.5 mg/kg, i.v.). Under tetanic stimulation (200 Hz; 15s), the pretetanic relative inhibition induced by apomorphine (200 ug/kg, i.v.) was increased only for a short period immediately after the cessation of tetanic stimulation. The results indicate existence of presynaptic dopamine receptors on the afferent terminals converging on the motoneurone which may functionally modulate the spinal motor output.

Animals↗
PubMed2003

Further evidence for enhancing effects of NO on monosynaptic and polysynaptic spinal reflexes in cats.

There are a number of studies on the effects of different NO donors and inhibitors on spinal cord with quite contradictory results. The aim of this study was to investigate the effects of sodium nitroprusside (SNP), a NO donor, and N(G)-nitro-L-arginine methyl ester (L-NAME), a nonselective NOS inhibitor, on monosynaptic and polysynaptic spinal reflexes in anesthetized and spinalized cats. After a dorsal laminectomy between L5 and S1, monosynaptic and polysynaptic spinal reflexes were evoked by stimulation of gastrocnemius nerves. Following control recordings, administration of L-NAME in 100, 200, 500 microM (local) and 10, 20, 50 mg/kg (i.v.) doses decreased significantly the monosynaptic and polysynaptic reflex amplitudes in a dose-dependent manner. Administration of SNP in 100, 200, 500 microM (local) and 100, 200, 500 microg/kg (i.v.) doses enhanced significantly the both reflex amplitudes in a dose-dependent manner. In another series of experiments it has been observed that the maximal decrease in reflex amplitudes caused by 500 microM local L-NAME administration in the 15th minute was reversed by locally administered SNP (500 microM). Our results support the hypothesis stating that NO may play a role in the modulation of mono- and polysynaptic spinal reflexes and the NO appears to have an enhancing role on these responses.

Animals↗
PubMed1975

Evidence for a monosynaptic mechanism in the tonic vibration reflex of the human masseter muscle.

Vibration of the masseter and temporalis muscles in normal human adult subjects elicits a tonic vibration reflex with unexpected features. The electromyographic response is not asynchronous as in the limb muscles, but involves well-defined spikes with a one-to-one temporal relation to the vibration cycles. The effect of various parameters such as muscle stretch, vibration frequency or amplitude, etc, has been investigated. The small latency fluctuation of the vibration-induced spikes is compatible with a monosynaptic reflex mechanism which is considered to be assisted by a polysynaptic facilitatory background of proprioceptive origin.

Adult↗
PubMed1964

NONSPECIFIC DEPRESSANT ACTION OF GAMMA-AMINOBUTYRIC ACID ON SOMATIC REFLEXES.

The effects of gamma-aminobutyric acid (GABA) on central integration of somatic reflexes in the cat have been studied by topical application, and by intrathecal or intracerebroventricular injection. Intrathecal injection of GABA inhibited the monosynaptic patellar reflex. The facilitation of the patellar reflex induced by strychnine, leptazol, tubocurarine and tetanus toxin was also inhibited. Polysynaptic facilitation of the patellar reflex induced in the spinal cat by electrical stimulation of the contralateral sciatic nerve was depressed by intrathecal GABA. Similarly, the supraspinal facilitation of the patellar reflex by electrical stimulation of the brain stem reticular formation was inhibited by application of GABA to the floor of the 4th ventricle. The polysynaptic inhibition of the patellar reflex at both levels was intensified by GABA. The flexor (tibialis anterior) reflex was depressed in the same manner as the extensor patellar reflex. The polysynaptic linguomandibular reflex was depressed by intracerebroventricular GABA. The depressant action of GABA at spinal and supraspinal levels of the neuraxis is discussed in relation to the role of GABA as an inhibitory transmitter in the central nervous system.

Aminobutyrates↗
PubMed1999

Different effect of high doses of naloxone on spinal reflexes in normal subjects and chronic paraplegic patients.

There is still controversy over the effects of naloxone on spinal reflexes in view of the fact that both facilitatory and inhibitory activities have been observed. Dosage, supraspinal influences and interactions with different opiate receptors may account for the different findings. We investigated the effect of placebo (saline) and high doses of naloxone (1.66 mg/kg) on the monosynaptic (H reflex) and nociceptive polysynaptic reflex (RIII reflex) in five normal subjects and three chronic paraplegic subjects. Following the administration of naloxone, there were no changes in the RIII reflex threshold in either group. By contrast, there was a marked facilitation of the H reflex amplitude in the normal subjects, but not in the spinal cord-injured subjects after treatment with naloxone. Saline induced no changes in the RIII reflex threshold or the H reflex amplitude in either of the two groups. Our data suggest that under normal conditions the opiatergic modulation of the nociceptive reflex is not functionally active whereas the tonic inhibitory modulation of the monosynaptic reflex is mediated by descending pathways.

Adult↗
PubMed1993

Pituitary adenylate cyclase activating peptide produces a marked and long-lasting depression of a C-fibre-evoked flexion reflex.

Pituitary adenylate cyclase activating peptide (PACAP) is a novel vasoactive intestinal peptide-like peptide. It has a neuronal localization and occurs in two forms, PACAP-38 and the C-terminally truncated PACAP-27. In a recent report we described a dense accumulation of PACAP-27-immunoreactive nerve fibres in the superficial layer of the dorsal horn in the spinal cord and a few PACAP-27-immunoreactive nerve cell bodies in the spinal ganglia in the rat. Double-immunostaining showed that immunoreactive PACAP-27 occurred in a subpopulation of the calcitonin gene related peptide/substance P-containing cell bodies and fibres. In this study, PACAP-27 (0.47-0.63 pmol) given intrathecally produced a significant and long-lasting suppression of C-fibre-evoked flexion reflex produced by the electrical stimulation of the plantar nerve and recorded as a reflex discharge in the peroneal nerve. With a higher dose, 1.25 pmol, the magnitude of the response was not increased further but the effect became longer-lasting. PACAP-38 and vasoactive intestinal peptide were tested in doses up to 5 pmol and produced a significant and, in the case of PACAP-38, long-lasting suppression of the spinal flexion reflex. PACAP-27 seemed to be much more potent than PACAP-38 and vasoactive intestinal peptide. Intrathecal PACAP-27 was without effect on the monosynaptic stretch reflex (evoked by electrical stimulation of the gastrocnemius nerve and recorded as a reflex discharge in the sciatic nerve), suggesting that its effect on the flexion reflex is specific.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

[Effects of 4'ethyl-2-methyl-3-piperidinopropiophenone on experimental rigidity and spinal cord activities (author's transl)].

Effects of 4'ethyl-2-methyl-3-piperidonopropiophenone hydrochloride (EMPP) on experimental rigidities in rats and spinal cord activities in cats were studied. EMPP in a dose range of 1.25 approximately 10 mg/kg i.v. reduced EMG spikes of the intercollicular decerebrate rigidity and anemic decerebrate rigidity in rats. In alpha-chloralose anesthetized cats, EMPP in a dose range of 2.5 approximately 10 mg/kg i.v. caused a dose-related inhibition of the flexor reflex without any effect on the patellar reflex. In spinal cats, 2.5 approximately 10 mg/kg of EMPP caused a dose-related inhibition of the flexor reflex but the potency was less than that in anesthetized cats. Oral administration of EMPP 100 approximately 200 mg/kg produced a selective inhibition of the flexor reflex and the effect was twice as potent as tolperisone and chlormezanone. On the other hand, EMPP at 2.5 approximately 10 mg/kg i.v. which had little effect on the patellar reflex inhibited both monosynaptic and polysynaptic reflex potentials recorded from the ventral root to the same extent and also depressed dorsal root reflex potential recorded from the dorsal root in spinal cats. EMPP reduced the frequency of spontaneous gamma-motoneurone discharges in spinal cats, but had no appreciable effect on GIa discharges from muscle spindle of the triceps surae muscle. These results indicate that EMPP reduces alpha- and gamma-efferent activities and that EMPP exerts a marked inhibitory effect on spinal cord activities acting on the spinal cord and supraspinal structures.

Action Potentials↗
PubMed1993

Recovery of stretch reflex responses following mechanical stimulation.

The recovery behaviour of mechanically evoked stretch responses was investigated. Stimuli which promoted identical dorsiflexing movements around the ankle joint were applied to ten subjects in two positions, seated and upright. The experimental sets comprised single as well as double dorsiflexing displacements. In the latter the stimuli were elicited for durations of either 100, 200 or 400 ms. Stretch responses following the first displacements were related to the stretch velocity but not to the amplitude. The responses of the plantar flexors following the second mechanical dorsiflexion were reduced with respect to the delay time between the first and second displacement. In addition, the magnitudes of these responses depended on the functional task: the stretch responses recovered much faster in the standing position when the triceps surae muscle was only slightly activated, whereas in the relaxed sitting position the reflexes remained suppressed. Both reciprocal inhibition, as well as the time course of the reformation of intrafusal cross-bridge links, may help to explain the depression of the monosynaptic stretch reflex.

Adult↗
PubMed1987

Effect of the synchronization of the discharges of single motor units for the formation of the summated electromyogram.

The monosynaptic electromyographic reflex (EMG) response to muscle stretching represents a synchronized discharge from the single motor units (MUs). The role of this synchronization, taking into account the effect of the subsequent voluntary activity, has been investigated by calculating the probabilities for the appearance of impulse from a single MU for consecutive 10 ms time intervals. Experimental data on the firing of the single MUs under stationary conditions and before the front of the summated EMG for m. triceps surae are used. The results obtained are compared with the experimental data on the interaction of the stretch reflex and the voluntary movement in response to the stretch. It is shown that the synchronization in itself cannot explain the later responses in the EMG, which are with latencies longer than the latency of the monosynaptic reflex, but shorter than the reaction time of the subsequent voluntary activity.

Electromyography↗
PubMed1978

Reciprocal inhibition during the tonic stretch reflex in the decerebrate cat.

1. The aim of this study was to investigate post-synaptic reciprocal Ia inhibition during the stretch reflex; particularly the extent to which an increased Ia excitation of the Ia inhibitory interneurones will be counteracted by recurrent inhibition from motor axon collaterals. For this purpose we investigated depression of monosynaptic test reflexes antagonist flexors (reciprocal inhibition) during static stretch of quadriceps or triceps surae in unanaesthetized decerebrate cats. 3. With increasing stretch of the extensor muscle there was first a linear augmentation of reciprocal inhibition, but along with the stretch reflex in the extensor a plateau appeared in the inhibition of the flexors, although the extensor stretch reflex (judged by the e.m.g.) increased with further stretching. Within the range of stretching of triceps surae which gave increased stretch reflexes the plateau in the reciprocal inhibition was usually maintained, while during stretching of quadriceps a second phase of augmenting reciprocal inhibition often appeared. Stretch beyond the level which increased the stretch reflex activity gave augmenting reciprocal inhibition both in case of quadriceps and triceps surae. 3. Excitability measurements from central terminals of Ia afferents revealed that the increasing reciprocal inhibition during increasing stretch reflex activity in quadriceps was associated with a primary afferent depolarization in knee flexor Ia afferents; there was no corresponding effect in ankle flexor Ia afferents during stretch reflexes in triceps surae. 4. The primary afferent depolarization evoked in knee flexor Ia afferents by electrical nerve stimulation was then compared with the presynaptic inhibition of knee flexor monosynaptic test reflexes produced by the same stimuli. The results suggest that the second phase of increasing reciprocal inhibition in knee flexors is due to presynaptic inhibition and accordingly that the depth of post-synaptic reciprocal inhibition remains constant at different degrees of stretch reflex activity in both knee and ankle extensors. 5. It is postulated that during increasing stretch reflex activity the increment in Ia excitation and recurrent inhibitio; on to the Ia inhibitory interneurones almost exactly balance each other. It is suggested that recurrent inhibition of Ia inhibitory interneurones may serve as a segmental autoregulatory mechanism to keep 'alpha-gamma-linked reciprocal inhibition' at a constant depth during different levels of agonist activity.

Animals↗
PubMedDate not supplied

Long-latency stretch reflex induced by tendon jerk in human triceps brachii muscle.

The electrical activity of the human triceps brachii muscle was recorded with surface electrodes in 14 healthy volunteers. Three experimental conditions were used to analyze muscle responses produced by tendon tap with an electromechanical hammer: 1) the muscle was at rest, 2) the subjects maintained an isometric tension for constant background EMG activity and 3) the subjects were asked to extend their arm in response to an acoustic signal occurring simultaneously with the tap. The analyses were performed with a computer. The monosynaptic tendon reflex had a mean latency of 12,5 ms. Later responses were observed with a mean latency of 62.8 ms. The later response observed in the extension experiments showed a synchronous EMG activity in comparison to the voluntary activity. It seems likely that proprioceptive impulses are of major importance in producing also the late responses since the method used minimalized cutaneous and joint afferent inputs.

Adolescent↗
PubMed1975

[Reflex mechanisms of interlimb interrelationships displayed in lumbar flexor centers of the cat spinal cord].

Interaction of segmental, propriospinal and spino-bulbo-spinal components of the lumbar flexor reflexes evoked by activation of the hind-and forelimb afferents with paired stimuli was studied in anesthetized cats. Coincidence in time of a reflex discharge evoked by stimulation of the forelimb afferent nerves with monosynaptic hindlimb flexor reflex causes considerable facilitation of the latter. The monosynaptic reflex increases for 40-50 ms. tthe polysynaptic flexor reflexes of segmental, propriospinal and spino-bulbo-spinal origin act upon each other in both a facilitatory and an inhibitory manner. Facilitation takes place only during the period of coincidence of the responses, inhibition when the responses are separated in time. Three types of inhibition with duration of 7-15, 40-150, 300-500 ms were observed. Possible neuronal mechanisms of interaction of the above-mentioned responses and their role in the inter limb interrelations are discussed

Animals↗
PubMed2005

Effect of spinal cord injury severity on alterations of the H-reflex.

The monosynaptic motoneuron response to stimulation of Ia afferents is known to be altered by spinal cord injury (SCI). Although the Hoffman (H)-reflex is a tool that is often used to measure this reflex in patients, there has not been a systematic study investigating the effect of SCI severity and time on the H-reflex. We used a clinically relevant model of spinal cord contusion (Mild and Moderate) as well as complete surgical transection to measure the H-reflex at 1, 4 and 8 weeks after injury. The H-reflex was recorded from rat hindpaw plantar muscles in order to measure the baseline reflex amplitude and its response to increased stimulus frequency, i.e. rate depression. We correlated the reflex amplitude at each frequency to spared white matter at the injury epicenter, hindlimb function and serotonin immunoreactivity associated with retrogradely labeled plantar muscle motoneurons. The three injury groups displayed different behavioral deficits and amount of spared white matter at all three times tested. H-reflex rate depression was abnormal in all three injury groups at all three time points. At 8 weeks, transected animals displayed more H-reflex rate depression than those with a mild contusion. Baseline H-reflex amplitude was increased in both contusion groups at 4 weeks and showed a positive linear correlation with serotonin immunoreactivity. This baseline amplitude was not increased after transection. Furthermore, in the contusion group, there was a U-shaped relationship between behavioral scores and H-reflex rate depression, suggesting that an intermediate sensitivity of the motoneuronal pool to afferent input is associated with better recovery of hindlimb function.

Analysis of Variance↗
PubMed1978

Forelimb reflexes modulated by tonic neck positions in cats.

The modulation of monosynaptic forelimb reflexes by tonic neck positions was investigated in cats with the head fixed. Lateral flexion of the body in a horizontal plane markedly facilitates reflexes of the deep radial nerve (DR) in the ipsilateral forelimb, while the antagonistic ulnar nerve (ULN) reflexes are strongly inhibited. Opposite effects are seen after contralaternal body movement. Dorsiflexion of the body clearly increases DR-reflexes and exerts a reciprocal although more pronounced inhibition on ULN reflexes. Opposite effects appear after ventriflexion. The reflex modulation starts with head-body displacements of approximately 5 degrees and increases with increasing angles. Furthermore reflex modulation does not depend on the intact cerebrum and cerebellum. The comparison of forelimb and hindlimb reflexes shows a decrease of the neck influences along the spinal cord.

Animals↗
PubMed1985

Pontomedullary raphe neurons: monosynaptic excitation from midbrain sites that suppress the jaw opening reflex.

The intracellular responses of pontomedullary raphe neurons to midbrain stimulation were studied in chloralose anesthetized cats. Electrical stimulation of the periaqueductal gray region at sites that suppressed the nociceptive jaw opening reflex evoked monosynaptic excitatory postsynaptic potentials in the majority of raphe neurons recorded. Intracellular labeling of studied cells demonstrated that recordings were obtained primarily from large and medium sized neurons in nucleus raphe magnus and the rostral nucleus raphe obscurus. These results provide further evidence that analgesia induced by periaqueductal gray stimulation may result in part from the direct activation of caudal raphe neurons.

Analgesia↗