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At least 325 records · Page 18Linked to original sources
PubMed1993

[The facilitation and inhibition of monosynaptic reflexes in the upper extremity of nursing infants].

The upper extremity H-reflex was investigated in healthy children, aged from 3 to 15 months. The electromyographic reflex responses of m. abduct or digiti min. and m. flexor carpi uln. were registered after electric stimulation of n. ulnaris. We constructed the curve of restoration of H-reflex after application of a couple of stimuli with equal duration and intensity, but over increasing intervals. We established changes in the excitation of H-reflex, obtained from m. flexor carpi uln., by increasing of the interval between the conditional and test stimuli. In the interval of 5 ms maximal facilitation was registered, while in the interval of 20 and 30 ms-maximal inhibition. In children aged from 3 to 9 months with persisting H-reflex in m. abductor digit min. we established possibility for its complete inhibition after application of a couple of stimuli with interval of 20 ms. In children aged from 9 to 15 months with vanished H-reflex in m. abductor digiti min. possibility for its obtaining was established after application of a couple of stimuli with interval of 5 ms. Quotation is made of evidences in favour of the hypothesis for the functional character of the disappearance of H-reflex in the small muscles of the arm in the first year of life of the children.

Arm↗
PubMedDate not supplied

Limitations in the use of CO2 as a method for studying the J-reflex.

In order to study the J-reflex, monosynaptic reflexes were recorded from L7 or S1 ventral root after stimulation of the posterior biceps, and semi-tendinosus nerve (PBST) from the lower limb in cats anaesthetized with Pentobarbitone sodium. Intratracheal CO2 (60 ml, 100%) depressed the monosynaptic reflexes, and the depression was comparable to the effects of right atrial phenyl diguanide injection. Bilateral vagotomy did not abolish the response showing that the afferent pathway of this depression does not travel via the vagus nerve. Thus it is concluded that CO2 cannot be used to study the J-reflex.

Animals↗
PubMed1981

Effect of epidural administration of bupivacaine (Marcaine) on monosynaptic reflex-depression.

The L5 and S1-segments of the spinal cord and relatively resistant to blockade. The extent and depth of the block are usually tested by pinprick. H-reflex depression (Hoffmann 1922, Magladery and McDougal 1950) was used to quantify differences between the 0.5%-solution and the 0.75%-solution of bupivacaine used for epidural anaesthesia. The H-reflex is a monosynaptic reflex representing the excitability of the motorneuron pool of the L5-S1 region of the spinal cord. Our results show a difference between the two concentrations favouring the 0.75% solution. The H-reflex is also a component in the complexity of control and servocircuits that play a role in the well-functioning of the spinal cord. Consequently we used its full recovery to rule out lasting toxic or irritating effects on the spinal cord. Bupivacaine 0.75% is not available in Europe whereas in the USA there is already wide experience in using this concentration. A comparison between 0.75% and 0.5% solutions reveals two important advantages in favour of the 0.75% solution: A higher intensity of motorblock [4, 15]. A lower incidence of incomplete blockade of the most resistant segments (L5-S1) [7, 8].

Action Potentials↗
PubMed1976

The relation between monosynaptic spinal reflex amplitudes and some EEG alpha activity parameters.

Some investigators have found that in normal human subjects the amplitudes of repetitively evoked tendon reflexes decrease as the number of evoked reflexes progresses. The question whether this decrement is a spinal phenomenon or that it can be ascribed to supraspinal influences that are related to the degree of cortical activation was investigated in two experiments designed to test whether a relation exists between the Hoffmann (H) and Achilles tendon (T) reflex amplitudes and EEG alpha activity parameters during a rest condition. The principal results can be summarized as follows: 1. A constant alpha index was accompanied by stable reflex amplitudes. 2. A decreasing alpha index was accompanied by decreasing reflex amplitudes. 3. A positive relation was found between H and T reflex amplitudes. 4. A positive relation was found between alpha index and alpha amplitude. 5. No circumscribed relation was found between the alpha wave period on the one side and the alpha index and amplitude on the other side. Apparently these relations are dependent on the state of activation of the subject. 6. The relations between the reflex amplitudes and the alpha parameters showed great interindividual differences.

Adult↗
PubMed1989

Modulation of spinal reflexes by pyramidal tract stimulation in an in vitro brainstem-spinal cord preparation from the hamster.

Electrophysiological evidence is presented showing that the pyramidal tract (PT) of the hamster modulates spinal reflexes in an in vitro brainstem-spinal cord preparation. Three spinal reflexes were studied. Stimulation of a dorsal root (DR) while recording from a ventral root (VR) of the same spinal segment evoked two reflexes: the monosynaptic reflex, and a long latency polysynaptic reflex. Stimulation of a DR while recording from a DR immediately rostral to it elicited a volley of antidromic discharges characteristic of the dorsal root reflex (DRR). The effect of PT stimulation on reflex transmission was tested by stimulating the PT at varying intervals prior to evoking a reflex. The results show that the amplitude of the monosynaptic reflex is progressively inhibited when preceded at shorter delays by a train of PT stimuli. Similarly, PT stimulation also suppresses the long latency reflex. In contrast, the PT facilities the DRR and repeated stimulation of the PT may evoke antidromic discharges recorded from the DRs. These data from the in vitro brainstem-spinal cord preparation indicate that the PT of the hamster exerts both inhibitory and facilitatory effects on reflex transmission in the spinal cord. The present study shows that it is possible to examine the descending control of spinal circuitry using an in vitro brainstem-spinal cord preparation.

Action Potentials↗
PubMed1989

[Characteristics of processes of excitation and inhibition of monosynaptic spinal reflexes after removal of the labyrinth].

Some electrophysiological changes were found within 1.0-1.5 hrs after removal of the labyrinth. The amplitude of extensor monosynaptic reflexes decreased. Recurrent inhibition weakened, amplitude of flexor monosynaptic reflexes increased, presynaptic inhibition decreased and recurrent inhibition was reinforced. Functional role of spontaneous influences of the labyrinth removal involves not only the reinforcement of extensor motoneurons but an increasing and stabilizing of reciprocal inhibition, restriction and stabilizing of reciprocal inhibition, restriction of information inflow and amplifying of differences of excitatory levels between active and passive reflex pathways.

Action Potentials↗
PubMed1999

Differential effects of (R)- and (S)-8-hydroxy-2-(di-n-propylamino)tetralin on the monosynaptic spinal reflex in rats.

We examined the effects of (R)- and (S)-8-hydroxy-2-(di-n-propylamino)tetralin hydrobromide (8-OH-DPAT) on the monosynaptic spinal reflex in rats. In intact rats, (R)-8-OH-DPAT (10 microg/kg, i.v.) enhanced the amplitude of the monosynaptic reflex, whereas at 100 microg/kg, it reduced the amplitude. (S)-8-OH-DPAT enhanced the monosynaptic reflex dose-dependently. In spinalized rats, (R)-8-OH-DPAT produced dose-dependent inhibition, but the (S)-enantiomer did not affect the monosynaptic reflex. Pretreatment with spiroxatrine or 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)butyl]-piperazine (NAN-190) inhibited (R)-8-OH-DPAT-induced monosynaptic reflex enhancement in intact rats, as did 5-hydroxytryptamine (5-HT) depletion. Ketanserin reduced the effect of (R)-8-OH-DPAT. These pretreatment regimens had no effect on the monosynaptic reflex depression produced by the (R)-enantiomer in intact and spinalized rats. Pretreatment with prazosin inhibited (S)-8-OH-DPAT-induced monosynaptic reflex enhancement in intact rats, as did noradrenaline and 5-HT depletion. These results suggest that supraspinal 5-HT1A receptors and the descending serotonergic system are involved in the stimulatory effect of (R)-8-OH-DPAT on the monosynaptic reflex, while both the descending serotonergic and noradrenergic systems, the latter acting via alpha1-adrenoceptors, are involved in the effect of the (S)-enantiomer on this reflex.

5,6-Dihydroxytryptamine↗
PubMed1977

Selective inhibition of the monosynaptic spinal reflex by a series of hydroxylated alkylaminoindans.

5-Hydroxy-2-piperidino-4,5,6,7-tetrahydroindan (5) and a number of related tetrahydro and dihydro compounds were prepared by selective mono- and dihydroxylation of the dihydro products from the Birch reduction of various alkylaminoalkylindans, tetralins, benzenes, and isoindolines. Some of these compounds showed a remarkably selective inhibition of monosynatpic spinal reflex in the segmental cat preparation.

Animals↗