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PubMed1983

Changes in segmental reflexes following chronic spinal cord hemisection in the cat. II. Conditioned monosynaptic test reflexes.

In a companion paper (Hultborn & Malmsten 1983) it was described that ventral root discharges to stimulation of peripheral nerves became larger on the side of a chronic spinal hemisection (left) than on the other side. In the present paper, based on the same experiments, conditioning of monosynaptic test reflexes was used to study changes of both excitatory and inhibitory effects on specified motoneuronal pools. Conditioning stimulation was given to IA afferents (reciprocal Ia inhibition, presynaptic inhibition of Ia fibers), high threshold muscle afferents, low and high threshold cutaneous afferents and motor axons (recurrent inhibition). A comparison of the efficacy of conditioning stimuli on the two sides showed that facilitatory effects were larger on the side of hemisection in a clear majority of cases. Inhibition was almost always either more efficient on the side of hemisection or equally efficient on the two sides. In control cats, facilitatory effects tended to be larger on the right side, while the results for inhibitory conditioning generally showed no clear side-bias. The increase in facilitatory effects after lesions may contribute to symptoms of spasticity.

Afferent Pathways↗

PubMed2006

Spinal cord injury-specific depression of monosynaptic spinal reflex transmission by l-5-hydroxytryptophan results from loss of the 5-HT uptake system and not 5-HT receptor supersensitivity.

We studied changes in the spinal segmental reflex and serotonergic (5-HT) responses in rats after spinal cord injury (SCI) produced by the weight-dropping method at the T8 level. The spinal monosynaptic reflex amplitude (MSR) was recorded from the L5 ventral root following stimulation of the ipsilateral L5 dorsal root. The 5-HT precursor l-5-hydroxytryptophan (L-5-HTP) depressed MSR in the spinal cord injured rats but not in normal rats. We investigated whether the SCI-specific depression of MSR by L-5-HTP was attributable to postsynaptic supersensitivity of 5-HT receptors or presynaptic loss of the 5-HT uptake system. Sumatriptan, a selective 5-HT(1B/1D) receptor agonist that is not taken up by 5-HT transporters, depressed the MSR similarly in both SCI and normal rats, suggesting that SCI resulted in the loss of 5-HT terminals and not postsynaptic supersensitivity of 5-HT receptors.

5-Hydroxytryptophan↗

PubMed1979

Monosynaptic spinal reflexes elicited at various phases of the EEG alpha cycle.

Relationships between the phase of EEG alpha waves and motor activities have been reported in the literature. In this study such a relation was investigated for electrically or mechanically evoked monosynaptic reflexes in the soleus muscle of normal humans. EEG alpha activity, derived from electrodes widespread over the ipsilateral and contralateral hemispheres, was tested but no relationships between alpha phase and reflex amplitudes were found.

Alpha Rhythm↗

PubMed1978

[Monosynaptic spinal reflex in epilepsy].

In 33 patients with generalized convulsive seizures a monosynaptic spinal reflex was studied. In an interattack period the author observed its clear asymmetry which was combined with a contralateral situation of epileptogenic focus on the EEG. In the majority of cases in patients with diffusive paroxysmal activity on the EEG asymmetry in the quantity of H-reflex was marked as well. The obtained data permit to recommend a study of H-reflex in an interattack period of epilepsy for specification of the topics of an epileptogenic focus.

Adolescent↗

PubMed1984

Identification and assessment of factors contributing to variability of the jaw jerk.

Unlike limb monosynaptic reflexes, the jaw jerk reflex ( JJR ) is extremely variable. We studied 35 healthy adults to determine the relative contributions of extrinsic and intrinsic factors underlying this variability. Each subject sat in a dental chair with his head and chin securely stabilized. Chin taps, delivered by a solenoid-driven plunger, were quantified with a piezo -transducer. The reflex response was recorded from surface electrodes over the right masseter muscle. A nasal thermistor signalled phases of respiration. Five of the 35 subjects had no reflex when relaxed, but during 15 degrees neck extension or voluntary contraction of the platysma muscle, a JJR appeared. The amplitude of the reflex varied considerably from trial to trial in all but one subject. A small component of this variability was due to minute changes in tap force despite head and chin stabilization and stimulus uniformity. Mean amplitudes of the reflex tended to increase with increases in tap force, but variability was large indicating intrinsic fluctuations in motoneuron excitability. Voluntary contraction of the platysma muscle and 15 degrees neck extension reliably enhanced the reflex. The JJR showed negligible respiratory modulation during quiet breathing. The reflex's variability in and among subjects precludes the use of the JJR as an index of masseteric motoneuron excitability. Our findings suggest that branchial motoneurons innervating the masticatory muscles receive far more diverse and fluctuating inputs than do somatic motoneurons innervating limb muscles.

Adolescent↗

PubMed2002

[Generators of walking movements in humans: spinal mechanisms of their activation].

The paper is focused on spinal generation of walking movements in patients afflicted with loss of supraspinal control consequent to back trauma. The author cites literature on methods of initiation of walking movements with pharmacological and proprioceptive stimulation. On his own experimental investigations with epidural electrical stimulation of the spinal marrow dorsal surface he proves existence of walking generators in the human. There is evidence that the walking pattern in extensors is formed through amplitude modulation of monosynaptic reflexes, whereas in flexors it is established through switching of the reflex paths from the monosynaptic reflex to the polysynaptic neuron network. Investigations of the functional deafferentation of lower extremities showed that walking movements as a result of epidural stimulation are intraspinal by origin and adjusted by way of peripheral feedback. A hypothetical sequence of activation of walking generators through the propriospinal system of dorsolateral and ventrilateral funiculi has been put forward.

Animals↗

PubMed1977

[State of the neuromuscular apparatus in Friedreich's familial ataxia (clinico-electromyographic analysis)].

The authors conducted a clinico-EMG study of 25 patients with Friedreich's familial ataxia. For this purpose with the aid of skin electrodes the distal muscles were studied. A supplementary study was made in 18 patients; the rate of the circulation of excitation along the motor fibres of the peripheral nerves and the monosynaptic-reflex were determined. In most of the studied patients there was a lesion of the peripheral motoneuron. The degree of the lesion depended mainly on the duration of the disease. The authors are of the opinion that the found disorders play a certain role in the mechanism of motor-coordinative disturbances in this disease.

Adolescent↗

PubMed1981

Comparison of monosynaptic tendon reflexes during preparation for ballistic or ramp movement.

Mechanism which underlie preparation for movement were studied in man using the method of 'monosynaptic tendon reflexes' during the preparatory period (PP) preceding the execution of ramp or ballistic tracking movements. Reflex reactivity is more important during the whole of the PP to a ramp rather than a ballistic movement; the increasing facilitation preceding the execution signal is greater and occurs earlier for the ramp than for the ballistic movement. These results were observed for 'fast' or 'slow' subjects in a reaction time task, but were more marked for the latter. On the one hand, preparation for movement is represented at the spinal level by a competition between activating influences, which allows for the speeding up of peripheral execution of central control, and inhibitory influences brought into play both by the need to suppress the movement until the execution signal and by the isolation of motor structures from postural proprioceptive servo-mechanisms. On the other hand, this preparation can imply a control of the level of activity in proprioceptive fusorial afferent pathways which depends on whether the movement to be executed is open-loop (ballistic) or closed (ramp). Comparison between the results obtained from fast and slow subjects underlines the importance of an active inhibitory process in spinal structures which would accompany temporal adjustment.

Female↗

PubMed2003

Serotonergic depression of spinal monosynaptic transmission is mediated by 5-HT1B receptors.

In the spinal cord, various subtypes of serotonin (5-hydroxytryptamine; 5-HT) receptors are involved in the modulation of motor output. Although the excitatory role of 5-HT(2) receptors is known, the receptor subtypes mediating the inhibitory effect of 5-HT on monosynaptic reflex transmission remain unclear. In this study, segmental spinal reflexes were recorded to examine the receptor subtypes underlying 5-HT-mediated inhibition of monosynaptic reflex transmission in spinalized rats. Under conditions of monoamine oxidase blockade with clorgyline, the 5-HT precursor L-5-hydroxytryptophan depressed the monosynaptic reflex. 3-Hydroxybenzylhydrazine dihydrochloride (NSD-1015), a centrally active decarboxylase inhibitor, abolished this inhibition, confirming that the depression of the monosynaptic reflex by L-5-hydroxytryptophan was due to 5-HT. In the presence of GR127935 or isamoltane, which show high affinity for 5-HT(1B) receptors, L-5-hydroxytryptophan did not suppress the monosynaptic reflex, whereas 5-HT(1A), 5-HT(1D), 5-HT(2) and 5-HT(7) receptor antagonists did not alter the inhibitory effect of L-5-hydroxytryptophan. These results suggest that serotonergic depression of monosynaptic reflex transmission is mediated by 5-HT(1B) receptors.

5-Hydroxytryptophan↗

PubMed1989

Presynaptic activation of the spinal serotonergic system in the rat by phencyclidine in vitro.

Electrophysiological studies were carried out to investigate the mechanism of action of phencyclidine [PCP; 1-(phenylcyclohexyl)piperidine] on a segmental monosynaptic reflex using isolated spinal cord preparations from neonatal rats. PCP and its related compounds produced a concentration-dependent depression of the monosynaptic reflex with a relative potency as follows: PCP = 1-[1-(2-thienyl)cyclohexyl]piperidine greater than 1-(1-m-aminophenylcyclohexyl)piperidine much greater than 1-(1-m-nitrophenylcyclo-hexyl)piperidine approximately MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate] much greater than (+)-N-allylnormetazocine. The N-methyl-D-aspartate receptor antagonists 2-amino-5-phosphonovalerate and 2-amino-7-phosphonoheptanoate had no effect on the monosynaptic reflex. The depression of the monosynaptic reflex by PCP was antagonized by serotonin (5-HT) receptor antagonists (methiothepin, spiperone and ketanserin) but unaffected by noradrenergic (phentolamine and timolol), dopaminergic (chlorpromazine and pimozide) and cholinergic antagonists (atropine and mecamylamine). Whereas 5-HT and a putative 5-HT releaser, p-chloroamphetamine, also depressed the monosynaptic reflex, the blockade of monoamine uptake by imipramine did not. Furthermore, pretreatment of rats with desipramine and 5,7-dihydroxytryptamine largely diminished the depression of the monosynaptic reflex by PCP and p-chloroamphetamine while enhancing the depressant action of 5-HT. These results suggest that PCP acts at sites located on presynaptic terminals of spinal serotonergic neurons, enhancing 5-HT release and thereby depressing the monosynaptic reflex.

5,7-Dihydroxytryptamine↗

PubMed2006

Improved organotypic cell culture model for analysis of the neuronal circuit involved in the monosynaptic stretch reflex.

Knowledge regarding neuronal circuit formation is central for the understanding of the vast network making up the brain. It is therefore necessary to find novel ways to analyze the mechanisms involved in well-defined neural circuits. We present an improved in vitro model of the monosynaptic stretch reflex circuit, based on primary organotypic cell cultures. By using limb tissue as a source of muscle fibers instead of circumspinal tissue we could make the in vitro system more in vivo like in the sense that it focuses on the stretch reflex involving limb muscles. Furthermore, our analyses showed that this procedure allows muscle fibers to follow the normal developmental pattern. Particularly interesting was the finding of slow tonic myosin heavy chain expressing muscle fibers, a developmental marker for muscle spindles, in the cultures showing that this system has the potential to contain the complete reflex circuits.

Animals↗

PubMed1985

Strychnine-like action of the convulsant barbiturate, CHEB.

The effect of 5-(2-cyclohexylideneethyl)-5-ethyl barbituric acid (CHEB) on the isolated spinal cord of the immature rat was examined using extracellular recording. At concentrations less than 20 microM CHEB increased the monosynaptic reflex (MSR) but depressed the reflex at greater concentrations (30-100 microM). At concentrations which enhanced the monosynaptic reflex, CHEB reduced the responses of motoneurones to glycine and to a lesser extent to those of L-glutamate. In the presence of strychnine (5 microM), which enhanced both mono- and polysynaptic reflexes, CHEB produced only slight enhancement of the monosynaptic reflex. At concentrations of 30-100 microM the responses to gamma-aminobutyric acid (GABA), glycine, L-glutamate and eledoisin-related peptide (ERP a substance P and analogue) were all reduced. At these concentrations CHEB directly depolarised the motoneurone membrane. Increases in [Mg2+]0, which reduced spontaneous activity, blocked the enhancement, by CHEB, of the monosynaptic reflex. The actions of CHEB in small doses may be due therefore to its ability to block the action of glycine and thus block tonic inhibition.

Amino Acids↗

PubMed1985

The effects of buspirone, BMY-13805 and 1-(2-pyrimidinyl)-piperazine on cat spinal reflexes.

Buspirone and its analog BMY-13805, clinically effective anxiolytics and their metabolite, 1-PP, were tested on cat spinal reflexes. In the spinal preparation, the monosynaptic reflex and the dorsal root potential were not changed by buspirone, BMY-13805 or 1-PP. Significant changes in the dorsal root potential and monosynaptic reflex were seen after buspirone administration in the intact neuraxis preparation. Generally, these changes had a bimodal pattern, a significant change within 1 hr after buspirone administration, then a period of remittance, followed by a second significant change 3 or more hr later. They included increases in the dorsal root potential and the following changes in the conditioned monosynaptic reflex: an increase in excitatory postsynaptic potential, an increase in postsynaptic inhibition, and decreases in presynaptic inhibition. These data indicate that buspirone does not affect these reflexes directly, but alters supraspinal mechanisms that regulate spinal reflexes.

Animals↗

PubMed1981

[Effect of drugs potentiating or inhibiting the activity of locus coeruleus neurons on various types of spinal inhibition in the cat].

Microinjections of aspartate or chlorpromazine (which increase the background firing of many central neurons) into region of locus coeruleus of decerebellized cats anaesthetized with chloralose diminished the inhibitory action of flexor reflex afferents on the extensor monosynaptic reflexes but had no effect on the excitatory action from these afferents on the flexor reflexes. In some experiments the injections of these drugs decreased also recurrent inhibition of extensor motoneurons. Microinjections of procaine or norepinephrine (which reduce the background of firing of central neurons) in the same region increased the inhibitory action of the flexor reflex afferents and the recurrent inhibition of the extensor monosynaptic reflexes and had no effect on their excitatory action on the flexor reflex. The role of tonic activity of locus coeruleus in controlling the spinal inhibition evoked from the flexor reflex afferents is discussed.

Animals↗

PubMed1988

Differing actions of convulsant and nonconvulsant barbiturates: an electrophysiological study in the isolated spinal cord of the rat.

The effects of various pairs of convulsant and nonconvulsant barbiturates on mono- and polysynaptic activity were studied in the isolated spinal cord of the immature rat, using extracellular recording. The convulsant barbiturates, 5-ethyl-5-(3-methylbut-2'-enyl) barbituric acid (3M2B), 5-ethyl-5-(1,3-dimethylbut-1'-enyl) barbituric acid (1,3M1B) and (+)-5-(1,3-dimethylbutyl)-5-ethyl barbituric acid [(+) DMBB] all increased the monosynaptic reflex at concentrations between 5 and 50 microM with no change in polysynaptic activity. When the concentration was raised to between 100 and 300 microM, however, the convulsants all reduced the monosynaptic reflex, thus producing a biphasic dose-response relationship. The nonconvulsant barbiturates phenobarbital, 5-ethyl-5-(3-methylbut-1'-enyl) barbituric acid (3M1B), amylobarbital (3MB) and (-)-5-(1,3-dimethylbutyl)-5-ethyl barbituric acid [(-)DMBB] produced only a decrease in mono- and polysynaptic reflexes. At concentrations which enhanced the monosynaptic reflex, the responses of motoneurones to glycine and eledoisin-related peptide (an analogue of substance P) were reduced by (+)DMBB, while 1,3M1B and 3M2B had no significant effects upon any of the neurotransmitters tested. At concentrations which depressed the monosynaptic reflex, the convulsants all reduced the response to glycine whereas the nonconvulsant barbiturates all increased the response to GABA. With the exception of phenobarbital, both convulsant and nonconvulsant barbiturates produced a direct depolarisation of the presynaptic terminal membrane, with only the convulsants producing a depolarisation of the membrane of the motoneurone. Using another convulsant barbiturate, 5-(2-cyclohexylideneethyl)-5-ethyl barbituric acid (CHEB), this direct depolarising action was found to be calcium-dependent.

Animals↗

PubMed1981

[Electrophysiological and pharmacological analysis of L-dopa-induced dyskinesia and tardive dyskinesia (author's transl)].

Electrophysiological and pharmacological analysis of L-Dopa-induced dyskinesia and tardive dyskinesia (L.DD) due to neuroleptics was performed on 12 patients with Parkinson's disease and on 12 others with psychotic diseases. This analysis included the examination of spinal reflexes, monosynaptic H reflex, polysynaptic cutaneous reflex of the lower limb, muscular responses to passive movement [stretch reflex and shortening reaction (SR)] and the study of the motor response to a dopaminergic stimulus (I.V. injection of Piribedil (PBD), a dopamine agonist). There was no difference in EMG activity between L.DD and TD. Three EMG patterns can be distinguished: anarchic discharge pattern (ADA), tonic grouping discharge pattern (AST) and rhythmic burst pattern (ABR). PBD effects indicate a possible relationship between the EMG patterns and the sensitivity level of the motor dopamine receptors. During L-Dopa dyskinesia and tardive dyskinesia, the same changes in spinal reflexes were observed. Muscle tone tested by muscular responses to passive movement (shortening and myotatic reaction) was normal. Monosynaptic excitability explored by H/M ratio was within the normal range. In contrast, the polysynaptic nociceptive reflex was increased in every case. In Parkinsonian patients with L-Dopa dyskinesia, this pattern of the spinal reflexes was significantly different in comparison to the rigid phase. Intravenous infusion of PBD suppressed tremor and provoked the occurrence of dyskinetic activity in Parkinsonian patients with L-Dopa dyskinesia during the rigid phase. During the dyskinetic phase, as in tardive dyskinesia, PBD increases these phenomena and changes EMG activity in rhythmic pattern. It is suggested that L-Dopa dyskinesia and tardive dyskinesia can be determined by testing EMG activity, spinal reflexes and dopaminergic reactivity. There is evidence to suggest that the various types of involuntary abnormal movement represent a single entity, and that dopamine receptor supersensitivity may be involved.

Antipsychotic Agents↗

PubMed1992

Stimulatory and inhibitory effects of serotonergic hallucinogens on spinal mono- and polysynaptic reflex pathways in the rat.

The effects of two 5-HT-related hallucinogens on rat spinal mono- and polysynaptic reflex pathways in the rat were investigated. 5-Methoxy-N,N-dimethyltryptamine (5-MeODMT, 1 and 100 micrograms/kg, i.v.), an indolealkylamine agent, produced a dose-dependent decrease in the monosynaptic reflex, whereas 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI, 1-100 micrograms/kg), a phenylalkylamine agent, produced a dose-dependent increase in the monosynaptic reflex. Both agents increased the polysynaptic reflex. The 5-HT2 receptor antagonists ketanserin (100 micrograms/kg) and ritanserin (100 micrograms/kg) blocked the effects of DOI on the monosynaptic reflex but only partially blocked the 5-MeODMT-induced effect on the monosynaptic reflex. These antagonists inhibited the change in polysynaptic reflex, induced by DOI but not by 5-MeODMT. Neither propranolol (1 mg/kg) nor 3-tropanyl-3,5-dichlorobenzoate (MDL 72222, 1 mg/kg) antagonized the effect of either agent. 5-Methoxy-N,N-dimethyltryptamine and DOI increased the excitability of motoneurons and this effect was inhibited by ketanserin. These results indicate that the two types of hallucinogens possess both common and distinct characteristics, with regard to their action on the spinal reflex: (1) both increase the activity of motoneurons through 5-HT2 receptors but (2) only 5-MeODMT has an inhibitory action on the pathway of the monosynaptic reflex.

Amphetamines↗

PubMed1981

Intramuscular localization of monosynaptic Ia reflex effects in the cat biceps femoris muscle.

Intracellular recordings form biceps femoris (BF) motoneurons were made in anesthetized low spinal cats during periods of electrical stimulation of the nerve branches supplying the anterior, middle and posterior portions of the BF muscle and the nerves to semimembranosus and semitendinosus. Measurements were made of each cell's composite intrahomonymous and heteronymous monosynaptic Ia-EPSP responses to stimulation of the test nerves (branches). We have found evidence for an intramuscular localization of these monosynaptic Ia reflex effects not only when comparing responses between the two functional components of the BF muscle as is well established [6] but, in addition, when comparing responses between different parts of each functional (hip extensor and knee flexor) component as well. It is argued that both somatotopic and neuronal recognition factors may contribute to the localization of these monosynaptic reflex effects.

Animals↗