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PubMed2003

Enhancement of carotid chemoreceptor reflex and cardiac chemosensitive reflex in the acute phase of myocardial infarction of the anesthetized rabbit.

In the acute phase of cardiac ischemia there is an imbalance of the autonomic outflow with a depression of the baroreceptor reflex. Carotid chemoreceptor stimulation evokes an increase on arterial blood pressure and bradycardia in the anesthetized and paralyzed animal. The activation of cardiac chemosensitive fibers elicit the Bezold-Jarisch reflex comprising a decrease of arterial blood pressure and bradycardia. In the present study, we studied the modifications of the carotid chemoreceptor reflex and the Bezold-Jarisch reflex elicited during the acute phase of myocardial infarction (MI) in the anesthetized and paralyzed rabbit. Rabbits were anesthetized with pentobarbitone, paralyzed and artificially ventilated. The carotid sinus region was exposed and a cannula was inserted retrogradely through the external carotid artery into the carotid bifurcation; the carotid body was stimulated by a lobeline injection. A catheter was advanced, via the right carotid artery, to the origin of the aorta and the Bezold-Jarisch reflex was evoked by an injection of ATP. The baroreflex was provoked by an increase in after-load or by clamping the common carotid artery. Heart ischemia was provoked by ligation of the descending coronary artery. Arterial blood pressure, carotid artery pressure, heart rate and electrocardiogram were monitored. Stimulation of cardiovascular and cardiac receptors was performed before and after coronary ligation. Results show an overall increase in the cardiovascular reflex responses elicited by stimulation of chemically activated receptors and an overall decrease of the baroreceptor responses after MI. In conclusion, these data show the existence of an enhancement of the reflex cardiovascular responses to carotid chemoreceptor and cardiac chemosensitive receptors stimulation and confirmed the depression of baroreceptor reflexes following heart ischemia that could account for the imbalance of the autonomic output observed in the acute phase of myocardial infarction.

Adenosine Triphosphate↗
PubMed1993

Electrical stimulation of the dorsal nerve of the penis evokes reflex tonic erections of the penile body and reflex ejaculatory responses in the spinal rat.

An animal model using the spinal rat was characterized. Electrical stimulation of the dorsal nerve of the penis elicited reflex tonic erections of the penile body and reflex bulbospongiosus muscle activity, flips and ejaculations. The tonic erections of the penile body are independent from contractions of the bulbospongiosus muscle and appear to be the result of a neurovascular process. Our observations suggest that reflex bulbospongiosus muscle activity, flips and ejaculations are a single complex reflex response, which we define as reflex ejaculatory response. Two parameters predicted the occurrence and type of reflex response. The visualization of bulbospongiosus muscle activity during surgical isolation of the dorsal nerve of the penis was sufficient to anticipate the elicitability of reflex ejaculatory responses. The latter, together with a systemic systolic pressure > or = 73 mmHg., warranted the elicitability of reflex tonic erections. The similarities found in the physiology of rat tonic penile body erections and of human erections make this model promising for further elucidation of sexual function. Moreover, the present model may prove useful for the investigation of neurogenic erectile dysfunction, and of neurogenic ejaculatory disorders.

Animals↗
PubMed1987

The flexor carpi radialis H-reflex in polyneuropathy: relations to conduction velocities of the median nerve and the soleus H-reflex latency.

In 80 controls latencies of flexor carpi radialis (FCR) and in 94 controls latencies of soleus H-reflexes correlated well with length of the extremity, body height and age. Multiple regression equations using latency as a variable dependent on age and body height can be best used in practice when both reflexes are employed for demonstration of proximal pathology. The majority (69%) of 93 patients with various polyneuropathies showed abnormalities in both reflexes illustrating that proximal nerve segments are frequently involved. Four per cent had abnormal FCR H-reflexes with normal soleus H-reflexes whereas the reverse was found in 19% of the patients. Abnormal FCR H-reflexes occurred with normal motor and sensory conduction velocities in the peripheral part of the median nerve in 14%, whereas the reverse was seen in 12%, indicating that FCR H-reflex examination is a valuable supplement to conventional conduction studies for detection of electrophysiologically existing pathology.

Action Potentials↗
PubMedDate not supplied

[Effect of the graded muscle contraction on the H reflex and long latency reflexes of the thenar and hypothenar muscles to a fixed threshold stimulus].

INTRODUCTION: To determine the percentage of appearance of the H reflex and long latency reflexes (LLRs) in the thenar and hypothenar muscles of normal subjects to a fixed threshold mixed nerve electrical stimulus and variable degrees of muscle contraction. METHODS: Fifteen subjects aged 21 to 32 years of age without any prior history of central or peripheral neurological diseases volunteered for the study. The stimulation was a constant currrent given at the wrist with the cathode positioned proximally; started at 1 mA and it was gradually increased mA by mA until the M response appeared with the subject relaxed. The intensity of the stimulation was thereafter kept constant. The contraction was an abducting movement of the thumb in the case of the thenar muscle and abduction of the digiti minimi in the case of the hypothenar muscle and was sustained throughout the study. The reflexes were elicited with a repetition rate of 3 Hz, the stimulus was a square pulse of 0.5 ms. We used a low frequency pass filter of 10 Hz and a high frequency pass filter of 10 kHz. The sweep speed was set a 10 ms per division. The responses were averaged 200 times and then smoothed. RESULTS: The mean intensity of the stimulus that evoked the H response, for all subjects, was 7.5 2.8 mA. The mean latency of the H reflex elicited with stimulation of the median nerve was 26 ms 2.03 ms (std. error 0.28, maximum 28.2, minimum 22.0). The mean latency of the H reflex elicited with stimulation of the ulnar nerve was 25.1 ms 1.64 ms (std. error 0.230, maximum 28, minimum 22.3). The difference between the percentage of responses attained under a relaxed condition and with any kind of muscle contraction was highly significant statistically using the Chi square method (p < 0.001). When we compared the percentage of the H responses obtained with slight, moderate, strong contraction, and contraction against resistance, between them, we did no find a significant difference. The LLRs appeared only in the trials with strong contraction. CONCLUSIONS: The H reflexes and the LLRs of the thenar and hypothenar muscle were not obtained with threshold stimulation when these muscles were relaxed. With any degree of muscle contraction the H reflex in these muscles could be obtained in 94 percent of the trials. Maximal contraction and contraction against resistance were the best conditions to elicit long latency responses.

Adult↗
PubMed1996

The influence of the asymmetric tonic neck reflex on the H-reflex in human temporal muscle.

In contrast to limb muscles, little is known about the role of the asymmetric tonic neck reflex (ATNR) on jaw-elevator muscles. The effect of rotation of the head on the H-reflex in the anterior part of the temporal muscle after masseteric nerve stimulation was evaluated. Eight healthy volunteers (7 males and 1 female, age range 18 to 27 years, mean age 22 years) participated. The masseteric M-response and the masseteric and temporal H-reflexes were elicited by stimulating the masseteric nerve using a monopolar needle technique. The electromyographic activity of the muscles was recorded by surface electrodes. The ATNR was modified by changing position of the head: 30 degrees rotation towards the stimulated side (+N), 30 degrees rotation towards the non-stimulated side (-N) and 0 degree central position (C). The heteronymous temporal H-reflex was elicited at a stimulus intensity of 120% maximal M-response at a frequency of 1 Hz, in random series of 5 to 20 sweeps, up to 30-50 sweeps for each position. On-line averaging was performed. A significant reduction of the H-reflex amplitude was observed in the -N position (p-0.02 paired "t"-test, p = 0.015 Wilcoxon signed rank test), while a significant increase was present in the +N position (p = 0.007 PTT and WSR). Also multivariate analysis yielded a significant influence of head rotation on H-reflex amplitude (p = 0.0032). It can be concluded that the ATNR has a significant influence on the H-reflex of the human temporal muscle.

Adolescent↗
PubMed2003

Foot-sole reflex receptive fields for human withdrawal reflexes in symmetrical standing position.

Human withdrawal-reflex receptive fields were assessed in 10 healthy subjects during standing with even support on both legs. Two electrical-stimulus intensities (1.2 and 2.2 times the pain threshold, PTh) were used. The painful stimuli were delivered in random order to 12 positions distributed over the foot sole. Tibialis anterior (TA), soleus (SO), vastus lateralis (VL), semitendinosus (ST), and iliopsoas (IL) reflexes were recorded. Further, the vertical force was recorded and the center or pressure (CoP) was assessed in the frontal and sagittal planes on both legs. Reflexes were observed at both intensities with the strongest reflexes at the high intensity. Around the ankle joint, SO reflexes dominated, which is in contrast to previous observations for subjects sitting. An unloading of the limb was found on the stimulated leg associated with a simultaneous loading of the contralateral leg. The shift in load was most pronounced for stimulation of the heel. The flexors ST and IL also had strong reflexes with reflex patterns correlated to the pattern of unloading. The shift in vertical force was accomplished by a move of the CoP in the anterior direction on the stimulated limb (contraction of SO), which simultaneously caused a small movement of the CoP in the lateral direction. In the present standing conditions, the ankle extensor played a dominant role in the withdrawal pattern in contrast to previous studies during sitting, relaxed conditions.

Adult↗
PubMed1980

Reflex heart block. Baroreflex, chemoreflex and bronchopulmonary reflex causes.

Reflex heart block was studied in 20 dogs anesthetized with sodium pentobarbital and in 5 trained unanesthetized dogs. Three different vagal reflexes were produced: the Marey response during hypertension caused by administering methoxamine, a cardiogenic hypertensive chemoreflex activated by injection of serotonin into the left atrium and the Hering-Breuer reflex observed during normal respiration of unanesthetized dogs. In every dog during any of the three reflexes heart block was consistently observed after the normal slowing response of the sinus node had been selectively eliminated by the direct perfusion of 10 microgram of atropine into the sinus node artery. This was a uniform response despite its being variously produced by a pressor reflex, a chemoreflex or an extracardiac bronchopulmonary reflex. Transient heart block is therefore to be anticipated during reflexes with vagal efferent components if for any reason the sinus node is incapable of slowing suitably. The possible clinical relevance of these experimental observations is discussed.

Animals↗
PubMed1992

Anourethral reflex. Description of a reflex and its clinical significance: preliminary study.

A new reflex which I call the 'ano-urethral reflex' is described and its clinical significance discussed. It was studied in 16 volunteers with normal vesical and rectal functions. A concentric needle electrode was introduced into the external and sphincter (stimulating), and another one into the external urethral sphincter (recording). The reflex response was recorded by EMG apparatus. The external urethral sphincter basal activity was increased with stimulation of the external anal sphincter. This reflex response was absent when the external and sphincter was anesthetised. The average latency of the reflex was 129.5 ms. Reflex urethral sphincter contraction at defecation guards against involuntary micturition which may result from rectal distension and levator contraction. The anourethral reflex can be a valuable diagnostic tool in routine investigations of patients with urological and proctological complaints.

Adult↗
PubMed1976

Asymmetric tonic labyrinth reflexes and their interaction with neck reflexes in the decerebrate cat.

1. Tonic labyrinth and neck reflexes were studied separately and in combination in the decerebrate cat with C1 and C2 spinal roots cut. Reflex effects were observed as changes in length of the isotonically loaded medial head of triceps. 2. The tonic labyrinth reflexes acted asymmetrically on the medial head of triceps. Side-down rotation of the head produced shortening in medial triceps, whereas side-up rotations of the head resulted in a lengthening. 3. The tonic neck reflexes acted asymmetrically on the medial head of triceps. Side-down rotations of the neck produced a lengthening of medial triceps, whereas side-up rotations of the neck resulted in shortening. 4. Labyrinth and neck reflexes produce opposite effects on the same limb extensor muscle so that, if the neck innervation is intact, head tilting produces no change in muscle length. 5. It is suggested that the interaction between the labyrinth and neck reflexes contributes to the stability of the trunk, allowing the head to move freely on the body without affecting this stability. Labyrinth and neck reflexes need therefore to be considered together as a single system.

Animals↗
PubMed1990

Neural mechanisms underlying the clasp-knife reflex in the cat. I. Characteristics of the reflex.

1. The goal of this study was to characterize the clasp-knife reflex by the use of stretch and isometric contraction of ankle extensor and flexor muscles in decerebrated cats with bilateral dorsal hemisections of their spinal cords at segment T12. 2. Stretch of an extensor muscle evoked inhibition in both homonymous and synergistic extensor muscles. The similarities between homonymous and synergistic inhibition suggest that similar neural mechanisms were responsible. 3. Homonymous and synergistic clasp-knife inhibition showed several characteristic features: 1) inhibition was evoked only by large stretches that produced significant muscle force. Short stretches that did not produce large forces evoked only excitation; 2) the magnitude of clasp-knife inhibition increased with increasing initial motor output, as reflected in the level of rectified EMG; 3) the time course of reflex inhibition evoked by ramp-and-hold stretch was characterized by segmentation of EMG during ramp stretch, dynamic overshoot of inhibition at the end-of-ramp stretch, and slow but usually complete decay of inhibition during maintained stretch; 4) inhibition persisted beyond the termination of stretch, and 5) inhibition showed adaptation to repeated stretch. 4. Isometric contraction of the soleus or medial gastrocnemius, produced by electrical stimulation of the muscle nerve, also evoked powerful synergistic-reflex inhibition via similar mechanisms as stretch-evoked, clasp-knife inhibition. Stretch evoked a greater degree of inhibition than did contraction, indicating that receptors responsive to both stretch and contraction contribute to clasp-knife inhibition. 5. The reflex effects produced by stretching the soleus or medial gastrocnemius were not confined to the homonymous and close synergistic muscles. Extensor muscles were inhibited and flexor muscles were excited throughout the hindlimb, which paralleled the pattern of a flexion-withdrawal reflex evoked by cutaneous stimulation. 6. Stretch of a flexor muscle, the tibialis anterior, evoked the same spatial pattern and time course of reflex action as stretch of an extensor muscle--inhibition of extensor muscles and excitation of flexor muscles throughout the hindlimb, including homonymous excitation of the tibialis anterior. 7. We conclude that neither Golgi tendon organs nor secondary spindle afferents are likely to contribute significantly to clasp-knife inhibition because their responses to stretch and isometric contraction differ from the reflex actions evoked by stretch and contraction.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1976

Electrically induced flexion reflex in gait training of hemiplegic patients: induction of the reflex.

Since the introduction of the concept of functional electrical stimulation, the use of multiple stimulation sites to activate several paretic muscles in a coordinated fashion during ambulation has been suggested. Rather than stimulating multiple muscles, we have applied a train of electrical pulses to a single skin area to activate several muscles simultaneously through the induction of a flexion reflex, and evaluated the effectiveness of this reflex in producing or assisting the swing phase of the gait cycle in the hemiplegic patient. Two considerations in selecting the best stimulus site were (1) the magnitude of the reflex as measured by the length of time the foot was off the floor following a stimulus and (2) the patient's tolerance to the stimulus. The magnitude of the reflex was proportional to the strength of the stimulus current in all skin areas tested; namely the sole, dorsum of the foot, and lower posterior thigh. Of the six patients tested a flexion reflex was not elicitable by sole stimulation in one and by posterior thigh stimulation in another. In every case, compared to the two other areas, stimulation of the sole was best tolerated and produced responses of equal or greater magnitude with the same intensity of current, even though larger voltages were required owing to greater tissue impedances. With a fixed frequency of 30 Hz, a pulse duration of 3 msec, and a stimulus current sufficient to produce the reflex, the duration of the reflex could be adjusted for each patient by varying the train duration from 100 to 700 msec. This technique offers a means of providing or assisting the swing phase in the gait training of the hemiplegic patient.

Aged↗
PubMed1989

Reflex changes in sympathetic activity affect the tooth tap-digastric reflex in rabbits.

We have previously shown that, in the anaesthetized rabbit, electrical stimulation of the sympathetic trunks inhibits the digastric opening reflex, as elicited by standardized tooth taps and monitored by integrated EMG. The site of action was most likely in the periodontal ligament, since the digastric reflex evoked by electrical stimulation of the inferior alveolar nerve was unaffected. In the present investigation we have studied the effects on the reflex of more naturally occurring changes in sympathetic activity, as induced by the baroreceptor reflex. The sympathetic discharge was increased by withdrawal of blood from the femoral vein, and reduced by electrical stimulation of the aortic baroreceptor nerve. Preliminary results in five rabbits showed that haemorrhage reduced the digastric reflex by more than 10% in 7 out of 13 tests (median 19%), while aortic nerve stimulation increased the reflex in 11 out of 13 tests (median 160%). It is therefore concluded that the tooth tap-digastric reflex may be affected also by more naturally occurring changes in sympathetic discharge.

Animals↗
PubMedDate not supplied

Participation of the beta-adrenergic receptor in the enteroruminal reflex and enteroenteric reflex.

In sheep with chronic fistulae of the small intestine and rumen the participation of the beta-adrenergic receptor was investigated in the enteroruminal reflex and enteroenteric reflex using the method of pharmacological analysis. The movements of the segments of the digestive tract with fistulae were recorded by the balloon method. A solution of hydrochloric acid administered into the ileum caused a reflex stimulation of its motor activity and inhibited the movements of the rumen. Intravenous administration of propranolol before instillation of the acid into the intestine abolished or reduced greatly the reflex inhibition of the movements of the rumen and in the small intestine it enhanced significantly the studied reflex reaction. Thus stimulation of the beta-adrenergic receptor plays an important role in the reflex stimulation of the motor activity of the rumen, and stimulation of the motor activity of the small intestine in the enteroenteric reflex is limited by the effects derived from this receptor.

Animals↗
PubMed1980

[Stapedius-reflex-audiometry by measuring the threshold for the re-inforcement of a pre-existing reflex (author's transl)].

The possibilities for predicting the pure tone threshold on the basis of the acoustic stapedius reflex threshold are improved by using two stimuli, e.g., white noise and pure tone, or two pure tones according to Sesterhenn and Breuninger. The principle of the monaural loudness summation with regard to the stapedius reflex was systematically examined with the aim to obtain the best suited range for clinical use with a double tone stimulus. The following procedure proved to be the most reliable one for an objective audiometry: A distinct reflex is produced by a basic pure tone of 4 kHz, 10 dB above its reflex threshold. The tone to be examined (1 kHz) was added with a delay of 0.5 s. A 1 kHz tone 28 dB below the reflex threshold (median) produced a clear re-inforcement of the basic reflex. Objective extrapolation possibilities from stapedius reflex threshold to pure tone threshold are thereby improved.

Acoustic Impedance Tests↗
PubMedDate not supplied

H-reflex recovery curve and reciprocal inhibition of H-reflex of the upper limbs in patients with spasticity secondary to stroke.

The H-reflex recovery curve of the lower limb is considered a useful test for the diagnosis of spasticity, and recently the reciprocal inhibition of the H-reflex has proven to be abnormal in patients affected with spasticity. We studied the H-reflex recovery curve and the reciprocal inhibition of the H-reflex in the upper limb of a group of 33 patients with different degrees of spasticity secondary to stroke. Results were compared with those of 25 controls. The aim of this study was to investigate if the two tests showed any direct correlation with the degree of spasticity and, furthermore, with other clinical measures that are present in patients with spasticity as part of an upper motoneuron syndrome (i.e., changes in muscle tone, reflexes, force, etc.). The results showed an abnormality of both tests in most patients (decrease of the three phases of inhibition in the reciprocal inhibition test and increase of the late facilitation part of the H-reflex recovery curve), and these abnormalities seem mostly to be related to muscle tone, most important being the degree of correlation between tone and changes in abnormality of the H-reflex recovery curve (P < 0.03).

Adult↗
PubMed1993

The recto-levator reflex: the description of a new reflex and its clinical application. Preliminary report.

This communication embodies the description of a technique of recording a new reflex which I call "recto-levator reflex". The study was performed on 32 normal volunteers. The technique comprises the introduction of a balloon connected with a catheter into the rectum. A concentric needle electrode was introduced into the levator ani. The rectal balloon was distended and the levator myoelectric activity was recorded. In 12 patients, the procedure was repeated after levator infiltration with xylocaine or saline. When the rectal balloon was inflated with air, the levator muscle contracted. Levator contraction increased with increasing rectal distension. Anesthetized muscle did not respond, while saline-infiltrated muscle responded to rectal distension. Latency of the reflex was calculated. The recto-levator reflex seems to play an important role at defecation. On rectal distension with stools, levator contraction opens the rectal neck. Changes in the latency or amplitude of the reflex would indicate a defect in the reflex pathway. The reflex may thus prove of diagnostic significance in defecation disorders.

Adult↗
PubMed2001

The blink reflex and the corneal reflex are followed by cortical activity resembling the nociceptive potentials induced by trigeminal laser stimulation in man.

Laser stimulation of the supraorbital regions evokes brain potentials (LEPs) related to trigeminal nociception. The aim of this study was to record the R2 component of the blink reflex and the corneal reflex in 20 normal subjects, comparing the scalp activity following these reflexes with the nociceptive potentials evoked by CO2 laser stimulation of supraorbital regions. Cortical and muscular reflexes evoked by stimulation of the first trigeminal branch were recorded simultaneously. The R2 component of the blink reflex and the corneal reflex were followed by two cortical peaks, which resembled morphologically N-P waves of LEPs. The two peaks demonstrated a difference in latency of approximately 40 ms, which is consistent with activation time of nociception. This finding suggests that these reflexes are induced by activation of small pain-related fibers.

Adult↗
PubMed1970

Reflex inhibition of monosynaptic reflexes by stimulation of type J pulmonary endings.

1. Monosynaptic reflexes, evoked from flexor and extensor hind limb muscle nerves in cats anaesthetized with pentobarbitone sodium, were depressed for several seconds after right intra-atrial injection of phenyl diguanide. Injection of the drug close to the aortic valves did not produce the same effect on the reflex. There was no obvious depression of polysynaptic reflexes on intra-atrial injection of phenyl diguanide.2. This depression of the monosynaptic reflex was present even after the administration of atropine, which lessened the hypotension due to phenyl diguanide. The blood gas tensions were also measured after the administration of phenyl diguanide, and were not altered to a degree where one would expect the depression to be secondary to a change in arterial gas tensions. The depression was also present in paralysed and artificially ventilated cats.3. The afferent pathway causing this depression of the monosynaptic reflex runs in the vagus nerve, as shown by experiments done before and after vagotomy. Intercollicular decerebration also abolished this inhibition of the monosynaptic reflex.4. Prior intravenous injection of strychnine (0.1 mg/kg) abolished the effect of intra-atrial administration of phenyl diguanide.5. It was concluded that stimulation of type J pulmonary endings causes a reflex inhibition of monosynaptic reflexes lasting for several seconds via regions of the brain cephalad to the intercollicular level.

Animals↗