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At least 199 records · Page 11Linked to original sources
PubMed1984

Sympathetic control of sexual reflexes: peripheral 6-hydroxydopamine administration facilitates the onset of penile reflexes in male rats.

The latency to display penile reflexes was significantly reduced in male rats tested one day following treatment with 6-hydroxydopamine (6-OHDA; 75 mg/kg, administered via acute tail vein injection). Eight days following treatment the latency to the first reflex in 6-OHDA treated males did not differ significantly from saline treated control subjects. There were no significant differences in the mean number of erections or flips displayed by 6-OHDA subjects when compared to saline treated control subjects. On tests one day after 6-OHDA administration, treated subjects displayed significantly fewer cups than control subjects on the corresponding tests. Chemical sympathectomy was verified by extreme reduction of peripheral norepinephrine levels. Results of this study are consistant with those reported for spinally transected rats tested under similar conditions (that is, one day following spinal transection), and suggest sympathetic inhibition of the onset of penile reflexes.

Animals↗
PubMed2000

Assessment of brainstem function in Chiari II malformation utilizing brainstem auditory evoked potentials (BAEP), blink reflex and masseter reflex.

Brainstem dysfunction was evaluated in 67 patients with myelomeningocele and Chiari II malformation using brainstem auditory evoked potentials (BAEP), blink reflex (BR) and masseter reflex (MR). Signs and symptoms related to Chiari II malformation were observed in 18 patients while 49 patients had normal brainstem findings. BAEP and BR showed a higher sensitivity of brainstem involvement than MR (BAEP=1.0, BR=0.83, MR=0.50). BR, and in particular, MR were of higher accuracy (BR=0.52, MR=0.72) than BAEP (0.39) in separating patients with brainstem signs and symptoms related to Chiari II malformation. We feel that this is due to anatomic and physiologic peculiarities of the brainstem structures mediating BR and MR. Our results suggest that brainstem reflexes can support the decision of further treatment.

Adolescent↗
PubMed2000

The clinical use of brainstem reflexes and hand-muscle reflexes.

Brainstem reflexes and hand-muscle reflexes can be elicited and recorded with routine EMG equipment. Not all these reflexes are useful in clinical neurology. But those that are - the subject of this review - exhibit distinct patterns of abnormality that have clinical diagnostic and localizing value in various diseases, including cranial neuropathies, focal lesions within the cervical cord, brainstem, and brain, movement disorders, and pain.

Adolescent↗
PubMed2001

Reflex and non-reflex elements of hypertonia in triceps surae muscles following acquired brain injury: implications for rehabilitation.

BACKGROUND: Following adult onset acquired brain injury, the triceps surae muscles tend to become shortened and exhibit increased resistance to passive lengthening; a phenomenon that has been termed 'hypertonia'. Spasticity (velocity dependent tonic reflex hyper-excitability) has traditionally been considered a major component of hypertonia. In addition, unmodulated descending excitatory influences on the alpha motorneurone pool may result in inappropriate or excessive muscle activity (dystonia). Non-reflex changes, secondary to the brain injury, and as a consequence of subsequent immobility, also take place in the passive and active elements of the muscle. These non-reflex changes affect the stiffness and extensibility of the musculo-tendinous unit. Atrophy of muscle fibres combines with collagen proliferation to produce increased muscle stiffness. This may be compounded by increased actin-myosin cross-bridge linkages, which are thought to be associated with reduced rates of cross-bridge detachment. Prolonged immobilization in a shortened position results in a loss of sarcomeres in series. Arthrogenic changes associated with disuse include remodelling of dense connective tissue and intra-articular adhesions. CONCLUSION: Decreased muscle extensibility may be exacerbated by muscle overactivity. Consideration of all of the potential factors contributing to hypertonia of the triceps surae muscle will assist clinicians to identify appropriate intervention strategies, which may facilitate better treatment outcomes.

Brain Injuries↗
PubMed2002

Prediction of the haemodynamic response to tracheal intubation: comparison of laser-Doppler skin vasomotor reflex and pulse wave reflex.

BACKGROUND: The laser-Doppler skin vasomotor reflex (SVmR) caused by tetanic stimulation of the ulnar nerve may be a test that can predict the haemodynamic response to tracheal intubation. A decrease in pulse wave amplitude (pulse wave reflex, PWR) may be an alternative index of this response. We compared the abilities of PWR and SVmR to predict the haemodynamic response to tracheal intubation and studied how alfentanil, muscle relaxation, stimulation site and stimulation pattern affected the two reflexes. METHODS: Anaesthesia was induced and maintained with 2% sevoflurane and 50% nitrous oxide in two groups of 10 ASA status 1 patients. Tetanic stimuli were applied to the flexor muscles of the forearm and the ulnar nerve before and after administration of vecuronium. The change in skin blood flow (laser-Doppler) and pulse wave amplitude (pulse oximetry) after a 5 and 10 s stimulation was measured on the opposite hand. If skin blood flow (laser-Doppler) decreased by more than 10%, a computer-controlled infusion of alfentanil was started and the target plasma concentration was increased in steps until this response was suppressed (< 10%). The trachea was intubated and arterial pressure and heart rate responses were recorded. Plasma alfentanil concentration was measured. RESULTS: When PWR and SVmR were suppressed, the haemodynamic response to tracheal intubation was reduced in 100 and 53% of patients respectively. PWR and SVmR responses decreased with increasing plasma alfentanil concentration. The SVmR response to muscle stimulation was reduced by muscle relaxants. The pulse wave response to both muscle and neural stimulation was reduced by relaxants. The responses to 5 and 10 s stimulations were similar. CONCLUSION: An absent SVmR does not predict a blunted arterial pressure or heart rate response to tracheal intubation. The PWR may be a better predictor.

Adult↗
PubMed1994

Utero-cervical inhibitory reflex. The description of a reflex and its clinical significance.

The functional relationship of the uterine corpus to the cervix was studied in 14 healthy women. The uterus was stimulated by an electro-myographic (EMG) needle electrode and the cervical pressure recorded by a balloon-tipped catheter. The test was repeated in seven women after the uterus had been anaesthetized. In the other seven patients, the response of both the uterine EMG and pressure to cervical dilatation was registered. The EMG needle electrode was then inserted into the cervix and the uterine pressure response to both stimulation and dilatation of the non-anaesthetized and anaesthetized cervix was recorded. Uterine muscle stimulation led to a cervical pressure drop from a mean of 15.8 +/- 6.6 to 5.3 +/- 2.2 cm H2O (P < 0.01). The cervical pressure did not respond to stimulation of the anaesthetized uterus. Cervical dilatation caused increase of the uterine pressure from a mean of 16.2 +/- 5.2 to 42.8 +/- 10.5 cm H2O (P < 0.01), whereas cervical stimulation effected a uterine pressure drop to a mean of 3.6 +/- 1.8 cm H2O (P < 0.01). Stimulation or dilatation of the anaesthetized cervix did not cause uterine pressure changes. The invariable cervical dilatation upon uterine stimulation suggests a reflex relationship which we have named 'utero-cervical inhibitory reflex' (UCIR). It seems that the reflex comes into action during labour and in conditions of uterine retention of blood or a dead ovum. Its impairment may interfere with cervical dilatation or lead to cervical incompetence. The UCIR could be included as an investigative tool in utero-cervical disorders.

Adult↗
PubMedDate not supplied

Conditioning the middle ear reflex at sensation levels below reflex threshold: air jet and electrical stimulation.

An ABAB functional analysis, conditioning and generalization, design was used in 3 experiments (2 were formal studies and 1 was empirical in nature) to investigate the conditionability of the middle ear reflex. The conditioned stimuli were subreflex threshold pure tones of various frequencies and intensities. The unconditioned stimulus (UCS) was an auricular air jet to the contralateral ear in the first experiment and cutaneous electrical stimulation to the ipsolateral, probe ear in the last 2 experiments. Reflexes were monitored by an otoadmittance meter, storage oscilloscope, and strip chart recorder. In the first experiment (air jet UCS), no subjects met the conditioning criterion within the maximum presentation of 400 paired trials, despite pilot evidence which indicated conditioning was feasible. In the second experiment (electrical stimulation UCS), 2 subjects met conditioning criterion; however, only one subject reconditioned and demonstrated partial generalization to other conditioned stimuli. In the third experiment (electrical stimulation UCS), one of 3 subjects who had previously been unconditionable with the air jet UCS met conditioning and reconditioning criterion and demonstrated partial generalization. Results indicate that the middle ear reflex can be conditioned to be elicited by subreflex threshold pure tones, however, results are limited.

Adult↗
PubMed2004

Effects of 3,4-methylenedioxymethamphetamine ('Ecstasy') on the jaw-opening reflex and on the alpha-adrenoceptors which regulate this reflex in the anesthetized rat.

Bruxism, principally jaw clenching, is frequently observed in users of the recreational drug 3,4-methylenedioxymethamphetamine (MDMA). It has been suggested that during bruxism a reduction of the activity of oral protective reflexes occurs. In this study we investigated the effects of intravenously administered MDMA on the digastric electromyographic responses elicited by orofacial electrical stimulation in the rat. We also assessed the effects of either the administration of a single dose (20 mg kg(-1), s.c.) or repeated doses of MDMA (same dose, twice a day, for 4 d) on the jaw-opening reflex (JOR) and on the sensitivity of the alpha(2)-adrenoceptors which, in an inhibitory way, regulate it. Increasing doses of MDMA (1-29440 micro g kg(-1)) induced an incomplete inhibition of JOR and 50% inhibition (ED(50)) at 2550 micro g kg(-1); maximal inhibition was 88%. The repeated treatment with MDMA led to an enhancement of the inhibition of JOR induced by the alpha(2)-agonist, clonidine (ED(50) was reduced by 77%), indicating an increased sensitivity of the alpha(2)-adrenoceptors. This study shows that the intravenous administration of MDMA reduces the JOR while repeated doses of the drug enhance the inhibitory noradrenergic mechanisms which regulate the reflex. The results also allow speculation that a reduction of JOR may underlie the occurrence of episodes of bruxism in MDMA users.

Adrenergic Uptake Inhibitors↗
PubMed1974

Interaction of baroreceptor and chemoreceptor reflexes. Modulation of the chemoreceptor reflex by changes in baroreceptor activity.

The purpose of this study was to determine whether the level of arterial pressure and degree of baroreceptor activation affect responses to stimulation of chemoreceptors. Chemoreceptors were stimulated by injecting nicotine into the common carotid artery of anesthetized and paralyzed dogs. Responses were observed in the innervated gracilis muscle, perfused at constant flow while perfusion pressure was measured. Arterial pressure was lowered by bleeding the animals and raised by transient occlusion of the descending aorta. Vasoconstrictor responses to stimulation of chemoreceptors were enhanced by hypotension and inhibited by elevation of arterial pressure. Potentiation of the chemoreceptor reflex by hemorrhagic hypotension was not the result of altered vascular resistance in the gracilis muscle, sensitization of chemoreceptors by catecholamines or acidosis, or changes in cerebral perfusion pressure. Additional studies were done in which we excluded the possibility that the changes resulted from direct effects of changes in arterial pressure on chemoreceptors. Both carotid bifurcations were isolated and perfused. On one side, pressure was raised to stimulate the carotid sinus baroreceptors. On the other side, the carotid body chemoreceptors were stimulated by nicotine or by hypoxic and hypercapnic blood. Activation of baroreceptors on one side attenuated the vasoconstrictor response to chemoreceptor stimulation on the other side. This excludes a direct effect of changes in arterial pressure on the chemoreceptors and suggests a central interaction of these reflexes. We conclude that vasoconstrictor responses to stimulation of chemoreceptors are potentiated by hypotension and inhibited by transient hypertension. These effects appear to result at least in part from a central interaction of chemoreceptor and baroreceptor reflexes.

Animals↗
PubMed2004

Effect of straining on diaphragmatic crura with identification of the straining-crural reflex. The "reflex theory" in gastroesophageal competence.

BACKGROUND: The role of the crural diaphragm during increased intra-abdominal pressure is not exactly known. We investigated the hypothesis that the crural diaphragm undergoes reflex phasic contraction on elevation of the intra-abdominal pressure with a resulting increase of the lower esophageal pressure and prevention of gastro-esophageal reflux. METHODS: The esophageal pressure and crural diaphragm electromyographic responses to straining were recorded in 16 subjects (10 men, 6 women, age 36.6 +/- 11.2 SD years) during abdominal hernia repair. The electromyogram of crural diaphragm was recorded by needle electrode inserted into the crural diaphragm, and the lower esophageal pressure by a saline-perfused catheter. The study was repeated after crural anesthetization and after crural infiltration with saline. RESULTS: The crural diaphragm exhibited resting electromyographic activity which showed a significant increase on sudden (coughing, p < 0.001) or slow sustained (p < 0.01) straining with a mean latency of 29.6 +/- 4.7 and 31.4 +/- 4.5 ms, respectively. Straining led to elevation of the lower esophageal pressure which was coupled with the increased electromyographic activity of the crural diaphragm. The crural response to straining did not occur during crural diaphragm anesthetization, while was not affected by saline infiltration. The lower esophageal pressure declined on crural diaphragm anesthetization. CONCLUSIONS: Straining effected an increase of the electromyographic activity of the crural diaphragm and of the lower esophageal pressure. This effect is suggested to be reflex in nature and to be mediated through the "straining-crural reflex". The crural diaphragm seems to play a role in the lower esophageal competence mechanism. Further studies are required to assess the clinical significance of the current results in gastro-esophageal reflux disease and hiatus hernia.

Action Potentials↗
PubMedDate not supplied

Cholecysto-sphincter inhibitory reflex: identification of a reflex and its role in bile flow in a canine model.

To study the effect of gallbladder (GB) distension on the sphincter of Oddi (SO), 9 mongrel dogs (mean weight 15.3+/-3.6 kg) were studied. Under anesthesia, the abdomen was opened and the GB and SO were exposed. A balloon-tipped catheter was introduced into the GB and a manometric catheter into the common bile duct so that its fluoroscopically controlled tip lay within the SO. The pressure response of the GB and SO to GB distension by the balloon without and with selective anesthetization of the GB and SO was recorded. The test was repeated in four vagotomized dogs. GB distension effected pressure rise within the GB and pressure drop within the SO. The GB pressure increased progressively as the distending volume increased, while the SO pressure drop was not affected. Selective anesthetization of the GB or the SO produced no SO pressure changes upon GB distension. The SO pressure response to GB distension after vagotomy was similar to that before vagotomy. The SO relaxation on GB contraction, being reproducible and abolished by selective anesthetization of either the SO or the GB, postulates a reflex relationship that we call the cholecysto-sphincter inhibitory reflex. This reflex seems to regulate the bile flow from the GB to the duodenum through the SO.

Animals↗
PubMedDate not supplied

The diagnostic value of stapedius reflex and stapedius reflex exhaustion in myasthenia gravis.

Authors studies impedance, stapedius reflex thresholds and stapedius muscle exhaustion on 31 ears of 16 MG patients. Investigations were carried out using GSI 33 computer-assisted middle ear analyzator. Stapedius reflex threshold values were increased in 93% of patients. Stapedius exhaustion was observed in 71% of patients. After the administration of the reversible cholinesterase inhibitor Mestinon (60 mg pyridostigmin bromide), reflex threshold decreased and exhaustion occurred in only 50% of cases. Authors review the literature in context with the audiometric diagnostics of MG and also recommend the use of these methods in more complicated ocular and bulbar cases of MG.

Acoustic Impedance Tests↗
PubMedDate not supplied

[Reflex myoclonic epilepsy in infancy: a new reflex epilepsy syndrome or a variant of benign myoclonic epilepsy in infancy].

CASE REPORTS: We report a clinical and EEG study of 8 children with reflex myoclonic epilepsy of infancy to further confirm the existence of this syndrome first described by Ricci et al in 1995. RESULTS: Between February 1990 to July 2002, we identified 64 epileptic patients with myoclonic seizures with an onset in the first six years of life. Eight (12.5%) of these patients had myoclonic seizure stimuli sensible. The seizures were characterized by generalized, myoclonic jerks triggered by tactile stimuli in six patients and acoustic stimuli in two, in one of them myoclonic jerks were triggered by both types of stimuli. The seizures appeared between 5 and 20 months of age. Two of the 8 patients had spontaneous myoclonic attacks during sleep. Interictal EEG was normal during wakefulness and occasional discharges were evident during sleep. In contrast, the ictal EEG during both wakefulness and sleep showed generalized spike wave and polyspike slow wave paroxysms. Neurologic examination, neuroimaging and neurometabolic studies were normal. Myoclonic jerks disappeared in 6 patients after valproic acid administration and in two after clobazan administration. Antiepileptic treatment was discontinued in 6 patients and no seizure recurrence was observed during a median follow up of 6 years. CONCLUSION: Our patients presented electro clinical criteria compatible with the syndrome of reflex myoclonic epilepsy of infancy. This syndrome could be considered to be a new reflex epileptic syndrome or a variant of benign myoclonic epilepsy in infancy.

Anticonvulsants↗
PubMed1976

[The pressor reflex induced by skeletal muscle contraction and its influence on the reflex from the sino-aortic zones].

The cardiovascular response to 10 sec tetanic muscular contractions was studied in the decerebrated cat. A pressor reflex about 30 mm Hg occurred during hindlimb contractions evoked by ventral roots (L6, L7, S1) stimulation. The pressor reflex was associated with a decrease of blood flow in working and resting muscles and a minimal changes of heart rate and left ventricular contractility. An increase of systemic resistance, as a main cause of pressor reflex is suggested. Static contractions of muscles and stimulation of muscle nerve evoked stronger inhibition of baroreflex than cutaneous nerve stimulation of nociceptive stimuli. Inhibition of the cardiac component of baroreflex during muscular exercise was shown.

Animals↗
PubMed1975

[Electrophysiological analysis of facial reflex in monkeys: trigemino-naso-labial reflex].

Electrical stimulation of the awake monkey's supra orbital nerve, elicits two successive reflex discharge in both naso-labialis muscles (NL). The responses have a similar high threshold. Similar responses are also elicited on electrical stimulation of the facial skin, whereas flash, click or tapping on the muscle belly are ineffective. These responses bear some resemblances to those obtained in orbicularis oculi muscles ; but the higher threshold and the different organization of the NL responses would suggest that such reflexes may serve a different function from that of the blink reflex.

Animals↗
PubMed1983

[Stapedius reflex. 1. Stapedius reflex threshold and recruitment].

UNLABELLED: The stapedius reflex threshold and pure tone threshold of 173 patients with normal hearing and cochlear disorders were examined (using Madsen ZO 73 equipment). CONCLUSIONS: 1. The aetiology of the cochlear hearing disorders does not influence the stapedial reflex threshold. 2. A linear regression between hearing loss and threshold difference was found in cochlear hearing disorders. 3. No correlation could be found between individual pure tone threshold and stapedial reflex threshold.

Adolescent↗
PubMed1983

[Stapedius reflex. 2. Latency periods of the stapedial reflex].

The reflex thresholds and initial latency times of the stapedial reflex of 50 patients with normal hearing and cochlear hearing loss were examined using Madson ZO 73 equipment. The following results were obtained: 1. The initial latency times of the stapedius reflex diminish proportional to the supra-threshold loudness. 2. No significant difference of the latency times was found between 0.5, 1, 2 and 4 kHz. 3. The initial latency times of patients with positive recruitment (cochlear hearing loss) do not differ from those of patients with normal hearing.

Auditory Threshold↗
PubMed2003

Study of the functional activity of the cecocolonic junction with identification of a "physiologic sphincter", "cecocolonic inhibitory reflex" and "colocecal excitatory reflex".

Radiologic, endoscopic and histomorphologic studies have suggested the presence of a sphincter at the cecocolonic junction (CCJ), while some investigators have denied its existence. To investigate the physiologic activity at the CCJ, the right colon was exposed during right hemicolectomy for early colonic cancer in 11 patients (mean age 43.6+/-12.3 years; 8 men). Three manometric catheters were introduced through colotomy to be separately located in the cecum, CCJ and ascending colon. We determined the CCJ pressure response to cecal and colonic distension by means of a balloon filled with saline in increments of 10 ml. The test was repeated after individual anesthetization of cecum, CCJ and ascending colon. The CCJ measured 1.6+/-0.6 cm in length and had a higher pressure ( p<0.05) than the cecum or colon. Large-volume cecal distension effected a significant CCJ pressure reduction which was augmented as the distension increased. Latency decreased upon increase of the distending volume. In contrast, the CCJ responded to large-volume colonic distension by pressure elevation which increased upon increase of the distending volume. Latency diminished with increased distension. Small-volume cecal or colonic distension effected no CCJ pressure response. The anesthetized CCJ did not respond to distension of the cecum or colon. Likewise, the CCJ did not exhibit a pressure response to distension of the anesthetized cecum or colon. The CCJ is a high-pressure zone which reacts to cecal or colonic distension by dilatation or narrowing, respectively. These data presumably denote the existence of a physiologic sphincter at the CCJ. We suggest that the CCJ pressure response to cecal or colonic distension is reflex and mediated through the cecocolonic inhibitory and colocecal excitatory reflexes, respectively. The role of the CCJ and related reflexes in colonic motility disorders needs to be studied.

Adult↗