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PubMed1976

Occurrence of the H reflex and the F wave in the rat.

In adult rats the tibial nerve was stimulated at the ankle and the evoked EMG of the foot muscles was recorded. A low threshold reflex discharge was elicited that was subsequently depressed by stronger stimuli eliciting the direct (M) wave. This discharge was abolished by cutting the dorsal roots (except for 1-3% postulated to be due to recurrent discharge). It had a central latency of about 2 msec, was depressed by stimulation rates above 0.3/sec and showed posttetanic depression, all of which are also properties of the rats's monosynaptic reflex. By analogy it is assumed to be an H reflex.

Animals↗
PubMed1955

Post-tetanic potentiation of polysynaptic reflexes of the spinal cord.

The phenomenon of post-tetanic potentiation has been studied in the cat spinal cord with particular reference to polysynaptic responses. Following tetanization of dorsal roots, these reflexes show an increased response, as measured in terms of their voltage-time area, with a predominant change in the earlier reflex pathways. Both of these changes in the reflex discharge have a time course of 15 to 25 seconds. Post-tetanic potentiation is also observed in response to stimulation of a dorsal rootlet following tetanization of another rootlet in the same or in a neighboring segment. This effect can be explained by post-tetanic changes in the terminals of secondary, and possibly higher order, internuncial cells, essentially similar to those changes in the primary afferent terminals which give rise to potentiation of the monosynaptic reflex.

Animals↗
PubMed1981

[Reorganization of segmental reactions to peripheral stimulation during fictive scratching in the cat].

Segmental reflex responses of the lumbosacral spinal cord to peripheral afferent stimulation were investigated in immobilized decerebrated cats before and after d-tubocurarine or bicuculline application to the upper cervical segments and during fictitious scratching evoked by mechanical stimulation of the pinna. Application of these drugs led to a decrease of N1 component of the cord dorsum potential, dorsal root potential and polysynaptic responses in efferent nerves. The appearance of fictitious scratching was accompanied by additional tonic inhibition of these reactions and against its background the modulation of amplitudes of segmental reactions depending on the fictitious scratching phase was observed. Modulation of monosynaptic reflexes was also observed during fictitious scratching. Mechanisms and physiological significance of retuning of segmental reflex responses during activation of a spinal scratching generator are discussed on the basis of the data obtained.

Animals↗
PubMed1988

Inhibitory effect of phencyclidine on rat spinal reflexes.

1. The effects of phencyclidine (PCP) on spinal reflexes and the excitability of motoneuron somata were studied in rats. 2. PCP decreased both the monosynaptic reflex (MSR) and the polysynaptic reflex (PSR) in spinal rats as well as in intact rats. 3. The effects of PCP were not antagonized by monoaminergic and cholinergic antagonists. 4. A low dose of PCP antagonized the PSR augmentation but not the MSR augmentation caused by N-methyl-D-aspartate (NMDA). 5. In the excitability test, PCP decreased not only the monosynaptic response but also the excitability of motoneuron somata. 6. These results suggest that the inhibitory effects of PCP on spinal reflexes are not due to mediation of the monoaminergic and cholinergic systems, but partly due to its blockade of NMDA-type receptors and also to a hyperpolarizing action or a membrane-stabilizing action on the motoneuron soma.

Animals↗
PubMed2004

Effects of propofol and sevoflurane on the excitability of rat spinal motoneurones and nociceptive reflexes in vitro.

BACKGROUND: Spinal actions of halogenated ethers are widely recognized, whereas spinal actions of intravenous anaesthetics like propofol are less clear. The aim of this study was to compare the spinal effects of propofol and sevoflurane. METHODS: We used an isolated spinal cord in vitro preparation from rat pups and superfused the anaesthetics at known concentrations. Responses of motoneurones to single and repetitive C-fibre intensity stimulation (trains of 20 stimuli at 1 Hz) of a lumbar dorsal root were recorded from the corresponding ventral root via a suction electrode. RESULTS: Stimulation trains produced a wind-up of action potentials in motoneurones. Both propofol and sevoflurane produced a significant concentration-dependent depression of the evoked wind-up, although at clinically relevant concentrations sevoflurane exhibited a larger intrinsic efficacy. Applied at anaesthetic concentrations, sevoflurane 250 micro M abolished action potentials whereas propofol 1 micro M only produced a reduction close to 50%. At these concentrations, sevoflurane produced a large depressant effect on the monosynaptic reflex whereas propofol was ineffective. CONCLUSIONS: Sevoflurane produces large inhibitory effects on nociceptive and non-nociceptive reflexes which are likely to contribute to immobility during surgery. Compared with sevoflurane, propofol appears to have much weaker effects on spinal reflexes such as those recorded in an isolated preparation.

Anesthetics, Inhalation↗
PubMed2004

[Gunshot injuries of peripheral nervous system: the questions of classification and diagnostics].

Two hundreds and sixty-seven patients with gunshot injuries of 394 nerves and plexus underwent clinical and electromyographic investigation and H-reflex evaluation as well. Based on the results of the data obtained, 3 types of nerves trunk injuries: neuroapraxia, axonothmesis and neurothmesis, were identified. The reduction of biopotential amplitude and synergic muscular activity, decrease of impulse conduction velocities (ICVeff--up to 30%), M-response amplitude (up to 50% and more) and motor units functioning were characteristic of neuroapraxia of nerve trunks. Axonothmesis of nerve trunks featured by the reduction of the amplitude and frequency of muscular biopotentials, decrease of its synergic activity, marked reduction of ICVeff (30--60%), rough fall of M-response amplitude and motor units functioning. In neurothmesis of nerve trunks, "bioelectrical silence" and disappearance of synergic muscular activity as well as an absence of M-response of denervated muscles were observed. An evaluation of monosynaptic reflex has a substantial significance for the determination of the level of low extremities injuries.

Adult↗
PubMed1989

Peripheral effects on the amplitude of monopolar and bipolar H-reflex potentials from the soleus muscle.

Variations in the amplitude of mono- and bipolarly measured H-reflex potentials can be influenced by muscle architecture and changes in muscle length. In the passive soleus muscle with the ankle joint fixed at 90 degree, the maximal-amplitude bipolar H-potentials were obtained along the midline of soleus at a distance of 2.0-4.0 cm below the insertion of the gastrocnemii on the Achilles tendon. In contrast, the optimal location of monopolar H-potentials was 5.0-8.0 cm below the gastrocnemii insertion. Stepwise passive shortening of soleus resulted in an increase in the amplitude of both H- and motor-unit potentials. This correspondence implicates peripheral factors, such as changes in muscle fibre diameter and inclination to the skin surface, as mechanisms mediating the changes in the amplitude of the potentials. Such effects necessitate caution in interpretation of the association between H-potential amplitude and monosynaptic reflex excitability.

Electric Stimulation↗
PubMed1979

Sural nerve effects on medial gastrocnemius motoneurones in the cat.

1. Excitability cycles for medial gastrocnemius motoneurones were recorded following sural nerve stimuli with amplitudes of 1.5, 3, 5, 10 and 40 times the nerve threshold. The monosynaptic reflex was time-integrated to quantify the motoneuronal output and some implications of this technique are discussed. In particular it is calculated that this method specifically examines the 15-25% most excitable motoneurones of the medial gastrocnemius pool.2. In most cases high amplitude stimulation of the sural nerve caused a triphasic (excitatory-inhibitory-excitatory) change in excitability. Arguments are given to support the conclusion that this represents a corresponding post-synaptic alteration in medial gastrocnemius motoneurone potential. It is concluded that this pattern illustrates the nature of the sural nerve projections to this portion of the medial gastrocnemius pool.3. The first period of excitation began after a latency, corrected to be compatible with intracellular recordings, of 2.8 ms and had a mean duration of 4.0 ms. The minimum stimulus level necessary for this effect lay between 1.5 and 3 times the nerve threshold. The maximum amplitude of this facilitation occurred with stimuli of 3-5 times threshold and was 60-90% of the amplitude of the monosynaptic facilitation which followed stimulation of the lateral gastrocnemius-soleus nerve.4. A period of inhibition followed immediately after the period of excitation and had a mean duration of 16 ms. The minimum stimulus level necessary for this effect lay between 1.5 and 3 times the nerve threshold and the degree of inhibition increased with stimuli up to 40 times threshold.5. The second period of excitation lasted a mean period of 50 ms and was due to activity in high threshold fibres. On average its amplitude was 50% that of the initial excitation.6. Exceptions to this triphasic variation of excitability were found. This result is interpreted as indicating the presence of projections with opposing actions which were simultaneously activated by sural stimuli.

Animals↗
PubMed2003

Participation of AMPA- and NMDA-type excitatory amino acid receptors in the spinal reflex transmission, in rat.

Classical in vitro and in vivo models and electrophysiological techniques were used to investigate the role of AMPA- and NMDA-type glutamate receptors in various components of spinal segmental reflex potentials. In the rat hemisected spinal cord preparation, the AMPA antagonists NBQX and GYKI 52466 abolished the monosynaptic reflex (MSR) potential but caused only partial inhibition of the motoneuronal population EPSP. NMDA antagonists had no noticeable effect on the MSR in normal medium, but markedly depressed the late part of EPSP. However, an NMDA receptor antagonist sensitive monosynaptic response was recorded in magnesium-free medium at complete blockade of the AMPA receptors. In spinalized rats, the AMPA antagonists completely blocked all components of the dorsal root stimulation evoked potential. MK-801 (2mg/kg, i.v.) reduced monosynaptic responses in a frequency dependent way, with no effect at 0.03 Hz and 22% inhibition at 0.25 Hz. The reduction of the di- and polysynaptic reflex components was about 30% and did not depend on stimulation frequency. Long-latency reflex discharge responses, especially when evoked by train stimulation, were more sensitive to MK-801 than the polysynaptic reflex. These results suggest that glutamate activates MSR pathways through AMPA receptors. However, under certain conditions, NMDA receptors can modulate this transmission through plastic changes in the underlying neuronal circuits. AMPA and NMDA receptors play comparable roles in the mediation of longer latency reflex components.

Action Potentials↗
PubMed1998

Muscle relaxant action of MS-322, a new centrally acting muscle relaxant, in rats.

1. The pharmacological properties of (R)-(+)-3-phenyl-5-¿2-(1-pyrrolidinylmethyl)-butyryl¿isoxazole hydrochloride (MS-322) were investigated and compared with those of other muscle relaxants. 2. MS-322 (3-12 mg/kg, IV) reduced spinal reflex potentials in acutely spinalized rats dose dependently. Its inhibitory effects on polysynaptic and dorsal root reflexes were more marked than those on the monosynaptic reflex. 3. MS-322 (1.5-12.0 mg/kg, IV) depressed the afferent discharges of de-efferented muscle spindles in anesthetized rats dose dependently. 4. The inhibitory effect of MS-322 on this afferent activity was considered to be due to its membrane stabilizing action. 5. In addition to the central effects of MS-322, its effect on muscle spindles may contribute to its muscle relaxant activity.

Animals↗
PubMed1992

Neuropsychopharmacological study of 2,4-dihydro[1,2,4]triazolo[3,4-c][1,4]benzothiazine-1-one (IDPH-791).

The neuropsychopharmacological profile of a new centrally acting skeletal muscle relaxant, 2,4-dihydro[1,2,4]triazolo[3,4-c][1,4]benzothiazine-1-one (IDPH-791), an analogue of triazolobenzothiazine, has been described and compared to mephenesin, a well known centrally-acting muscle relaxant. IDPH-791 was found to be safer and of longer duration of action than mephenesin in all the tests conducted in this study. Both IDPH-791 and mephenesin caused ataxia, decrease in spontaneous activity and inhibition of pinnal reflex. IDPH-791 was 1.5 to 2.0 times more potent in exhibiting motor inco-ordination and anticonvulsant activity than mephenesin in mice and rats. IDPH-791 was twice as active in inhibiting various spinal polysynaptic reflexes, crossed extensor, flexor, and linguomandibular reflexes; however, both did not affect the typical monosynaptic reflex, patellar reflex. IDPH-791 and mephenesin did not have sedative activity. Although mephenesin exhibited haemolytic activity, IDPH-791 was devoid of this activity. It is concluded that IDPH-791 is a safe and effective centrally-acting muscle relaxant having a longer duration of action than mephenesin. IDPH-791 is also devoid of sedative and haemolytic activity.

Administration, Oral↗
PubMed1986

Functional recovery of locomotive behavior in the adult spinal dog.

Complete transection of the midthoracic spinal cord was performed on adult female dogs. Development of reflexes and locomotive movements in the hindlimbs after spinal transection was investigated over several months. In the earlier stages after the surgery, dogs showed flaccid paralysis of the hindlimbs. Within several weeks, muscle tone of the hindlimbs was gradually increased accompanied by development of flexion reflex with after-discharge in addition to monosynaptic reflexes. Alternating stepping movement also began to develop. Afterward, extensor thrust and crossed extension reflex were observed. Standing behavior of the hindlimbs was found after enough development of the extensor thrust and correct placement of the pads of the toes. Steady development of stepping and standing caused forward locomotion using fore- and hindlimbs. This walking behavior of the hindlimbs was never inhibited by additional spinal cord transection. These findings indicate that the isolated spinal cord caudal to the transected site is responsible for the locomotive behavior of the hindlimbs in adult spinal dogs. Spinal automatism and development of responses induced by afferent inflow from outside the cord may help to explain such functional recovery of the paralyzed hindlimbs.

Animals↗
PubMed1978

Specificity of afferent and efferent regeneration in the cockroach: establishment of a reflex pathway between contralaterally homologous target cells.

1. In 132 cockroaches the main leg nerve on one side (right), of the metathoracic segment was crossed to the opposite (left) side and allowed to regenerate. In 3-8 wk, 59% of the animals displayed reflex activity in the left leg (behaviorally demonstrated by leg withdrawal following tarsal stimulation). 2. EMGs from the femoral extensor revealed potentials characteristic of normal activity in the extensor, which is innervated by an identified motor neuron, Ds. 3. Intracellular recordings from processes within the right hemiganglion of the metathoracic ganglion (CNS) demonstrated 1:1 activity between a unit in the CNS recording and the EMG of the left extensor. Subsequent intracellular staining revealed that the unit was on the right side of the CNS and was identified as motor neuron Ds by the location of its soma and dendrites. This finding indicated that specific, contralateral, efferent reinnervation occurs in the cockroach. 4. In normal cockroaches a monosynaptic reflex exists between hair plate afferents and Ds. A temporal analysis (stimulus-interval histogram) indicated that the reflex is also established in the crossed-regenerated animals. These data suggested that specific contralateral afferent reinnervation also occurs in the cockroach and that the monosynaptic nature of the normal reflex was reestablished. 5. Therefore, cell-to-cell specificity in neuron-to-neuron or neuron-to-muscle interactions not only occurs in normally developing or regenerating animals but also occurs between contralaterally homologous target cells, given the proper experimental conditions. It is also suggested that this experimental procedure of redesigning pathways may be a useful tool for further studies of behavior.

Afferent Pathways↗
PubMed1983

[Study of participation of reflex mechanisms in postinhibitory rebound by analyzing the activity of individual human motor units].

The mechanism of postinhibitory rebound after maximal and submaximal for M-response nerve stimulation was studied on firing motor units of hand muscles (m. abd. poll. br., m. abd. dig. min.) and leg muscles (m. soleus, m. rect. fem.) of healthy people. The poststimulus histograms and changes in an interspike interval duration were compared with time course of a twitch mechanogram. In all muscles under strong evoked twitch the only cause of the burst following the silent period was the synchronous motoneuron escape from inhibition. Under strong muscle twitch a true motoneuron facilitation was revealed. It is suggested that this is a reflex response to muscle extending in muscle relaxation phase after induced twitching. In leg muscles the revealed facilitation had a latency of spinal monosynaptic reflex with regard to the supposed moment of the burst in spindle afferents. In hand muscles (with H-reflex known to be suppressed in a normal man) the adequate activation of spindles during muscle relaxation caused facilitation only with the latency of polysynaptic reflex. These data are in accordance with a hypothesis on supraspinal presynaptic inhibition of monosynaptic action of spindle afferents in motoneurons of some human muscles.

Electric Stimulation↗
PubMed2006

Spinal cord reflexes induced by epidural spinal cord stimulation in normal awake rats.

Motor responses in hindlimb muscles to epidural spinal cord stimulation in normal awake rats during bipedal standing were studied. Stimulation at L2 or S1 induced simultaneous and bilateral responses in the vastus lateralis, semitendinosus, tibialis anterior, and medial gastrocnemius muscles. Stimulation at S1 evoked an early (ER), middle (MR) and late (LR) response: stimulation at L2 elicited only a MR and LR. Vibration and double epidural stimulation testing suggests that the ER is a direct motor response, whereas the MR and LR are mediated synaptically. MR has properties of a monosynaptic reflex, i.e., inhibited during vibration and depressed during the second pulse of a double stimulation. Some components of the LR seem to be mediated by afferents associated with the flexor reflex and probably involve group II afferents. During bipedal treadmill stepping, the MR was modulated in extensors, whereas the LR was modulated in flexors. These results show differential modulation of monosynaptic and polysynaptic reflexes in flexor and extensor motor pools during locomotion. Monosynaptic responses to stimulation at either L2 or S1 generally were amplified in extensors during the stance phase and in flexors during the swing phase of the step cycle. No correlation was found between the ER and the EMG background during stepping, whereas both the MR and LR were closely correlated with the changes in the EMG activity level of the corresponding muscle. These data demonstrate the feasibility of using epidural stimulation for examining monosynaptic and polysynaptic pathways to motor pools associated with multiple muscles during movement and over a prolonged period.

Afferent Pathways↗