Fictive Scratching Patterns in Brain Cortex-Ablated, Midcollicular Decerebrate, and Spinal Cats.

Background: The spinal cord's central pattern generators (CPGs) have been explained by the symmetrical half-center hypothesis, the bursts generator, computational models, and more recently by connectome circuits. Asymmetrical models, at odds with the half-center paradigm, are composed of extensor and flexor CPG modules. Other models include not only flexor and extensor motoneurons but also motoneuron pools controlling biarticular muscles. It is unknown whether a preferred model can explain some particularities that fictive scratching (FS) in the cat presents. The first aim of this study was to investigate FS patterns considering the aiming and the rhythmic periods, and second, to examine the effects of serotonin (5HT) on and segmental inputs to FS. Methods: The experiments were carried out first in brain cortex-ablated cats (BCAC), then spinalized (SC), and for the midcollicular (MCC) preparation. Subjects were immobilized and the peripheral nerves were used to elicit the Monosynaptic reflex (MR), to modify the scratching patterns and for electroneurogram recordings. Results: In BCAC, FS was produced by pinna stimulation and, in some cases, by serotonin. The scratching aiming phase (AP) initiates with the activation of either flexor or extensor motoneurons. Serotonin application during the AP produced simultaneous extensor and flexor bursts. Furthermore, WAY 100635 (5HT1A antagonist) produced a brief burst in the tibialis anterior (TA) nerve, followed by a reduction in its electroneurogram (ENG), while the soleus ENG remained silent. In SC, rhythmic phase (RP) activity was recorded in the soleus motoneurons. Serotonin or WAY produced FS bouts. The electrical stimulation of Ia afferent fibers produced heteronymous MRes waxing and waning during the scratch cycle. In MCC, FS began with flexor activity. Electrical stimulation of either deep peroneus (DP) or superficial peroneus (SP) nerves increased the duration of the TA electroneurogram. Medial gastrocnemius (MG) stretching or MG nerve electrical stimulation produced a reduction in the TA electroneurogram and an initial MG extensor burst. MRes waxed and waned during the scratch cycle. Conclusion: Descending pathways and segmental afferent fibers, as well as 5-HT and WAY, can change the FS pattern. To our understanding, the half-center hypothesis is the most suitable for explaining the AP in MCC.

Hind limb motoneurons activity during fictive locomotion or scratching induced by pinna stimulation, serotonin, or glutamic acid in brain cortex-ablated cats.

In brain cortex-ablated cats (BCAC), hind limb motoneurons activity patterns were studied during fictive locomotion (FL) or fictive scratching (FS) induced by pinna stimulation. In order to study motoneurons excitability: heteronymous monosynaptic reflex (HeMR), intracellular recording, and individual Ia afferent fiber antidromic activity (AA) were analyzed. The intraspinal cord microinjections of serotonin or glutamic acid effects were made to study their influence in FL or FS During FS, HeMR amplitude in extensor and bifunctional motoneurons increased prior to or during the respective electroneurogram (ENG). In soleus (SOL) motoneurons were reduced during the scratch cycle (SC). AA in medial gastrocnemius (MG) Ia afferent individual fibers of L6-L7 dorsal roots did not occur during FS Flexor digitorum longus (FDL) and MG motoneurons fired with doublets during the FS bursting activity, motoneuron membrane potential from some posterior biceps (PB) motoneurons exhibits a depolarization in relation to the PB (ENG). It changed to a locomotor drive potential in relation to one of the double ENG, PB bursts. In FDL and semitendinosus (ST) motoneurons, the membrane potential was depolarized during FS, but it did not change during FL Glutamic acid injected in the L3-L4 spinal cord segment favored the transition from FS to FL During FL, glutamic acid produces a duration increase of extensors ENGs. Serotonin increases the ENG amplitude in extensor motoneurons, as well as the duration of scratching episodes. It did not change the SC duration. Segregation and motoneurons excitability could be regulated by the rhythmic generator and the pattern generator of the central pattern generator.

Neurophysiological aspects and their relationship to clinical and functional impairment in patients with chronic obstructive pulmonary disease.

OBJECTIVE: The purpose was to assess functional (balance L-L and A-P displacement, sit-to-stand test (SST) and Tinetti scale - balance and gait) and neurophysiological aspects (patellar and Achilles reflex and strength) relating these responses to the BODE Index. INTRODUCTION: The neurophysiological alterations found in patients with chronic obstructive pulmonary disease (COPD) are associated with the severity of the disease. There is also involvement of peripheral muscle which, in combination with neurophysiological impairment, may further compromise the functional activity of these patients. METHODS: A cross-sectional study design was used. Twenty-two patients with moderate to very severe COPD (> 60 years) and 16 age-matched healthy volunteers served as the control group (CG). The subjects performed spirometry and several measures of static and dynamic balance, monosynaptic reflexes, peripheral muscle strength, SST and the 6-minute walk test. RESULTS: The individuals with COPD had a reduced reflex response, 36.77 ± 3.23 (p < 0.05) and 43.54 ± 6.60 (p < 0.05), achieved a lower number repetitions on the SST 19.27 ± 3.88 (p < 0.05), exhibited lesser peripheral muscle strength on the femoral quadriceps muscle, 24.98 ± 6.88 (p < 0.05) and exhibited deficits in functional balance and gait on the Tinetti scale, 26.86 ± 1.69 (p < 0.05), compared with the CG. The BODE Index demonstrated correlations with balance assessment (determined by the Tinetti scale), r = 0.59 (p < 0.05) and the sit-to-stand test, r = 0.78 (p < 0.05). CONCLUSIONS: The individuals with COPD had functional and neurophysiological alterations in comparison with the control group. The BODE Index was correlated with the Tinetti scale and the SST. Both are functional tests, easy to administer, low cost and feasible, especially the SST. These results suggest a worse prognosis; however, more studies are needed to identify the causes of these changes and the repercussions that could result in their activities of daily living.

Neurophysiological aspects and their relationship to clinical and functional impairment in patients with chronic obstructive pulmonary disease

OBJECTIVE: The purpose was to assess functional (balance L-L and A-P displacement, sit-to-stand test (SST) and Tinetti scale - balance and gait) and neurophysiological aspects (patellar and Achilles reflex and strength) relating these responses to the BODE Index. INTRODUCTION: The neurophysiological alterations found in patients with chronic obstructive pulmonary disease (COPD) are associated with the severity of the disease. There is also involvement of peripheral muscle which, in combination with neurophysiological impairment, may further compromise the functional activity of these patients. METHODS: A cross-sectional study design was used. Twenty-two patients with moderate to very severe COPD (>60 years) and 16 age-matched healthy volunteers served as the control group (CG). The subjects performed spirometry and several measures of static and dynamic balance, monosynaptic reflexes, peripheral muscle strength, SST and the 6-minute walk test. RESULTS: The individuals with COPD had a reduced reflex response, 36.77±3.23 (p<0.05) and 43.54±6.60 (p<0.05), achieved a lower number repetitions on the SST 19.27±3.88 (p<0.05), exhibited lesser peripheral muscle strength on the femoral quadriceps muscle, 24.98±6.88 (p<0.05) and exhibited deficits in functional balance and gait on the Tinetti scale, 26.86±1.69 (p<0.05), compared with the CG. The BODE Index demonstrated correlations with balance assessment (determined by the Tinetti scale), r = 0.59 (p<0.05) and the sit-to-stand test, r = 0.78 (p<0.05). CONCLUSIONS: The individuals with COPD had functional and neurophysiological alterations in comparison with the control group. The BODE Index was correlated with the Tinetti scale and the SST. Both are functional tests, easy to administer, low cost and feasible, especially the SST. These results suggest a worse prognosis; however, more studies are needed to identify the causes of these changes and the repercussions that could result in their activities ...

Is the maturation of monosynaptic stretch reflex in rats affected by neonatal malnutrition?

We compared the maturation of the monosynaptic stretch reflex in control rats and in rats submitted to neonatal malnutrition. Electrical stimulations of the sciatic nerve were applied in wakeful rats of different ages (21-90 days) to record, by surface electrodes, the maximal direct motor response (M(max)) or the maximal Hoffmann reflex (H(max)). Percussion on the Achilles tendon induced the T-reflex. Animals submitted to neonatal malnutrition showed significant reductions in H-reflex latency and in velocity index of nervous conduction. The H- or T-reflex amplitudes were lower for malnourished rats of 21 days but the difference was significant only for the T(max)/M(max) ratios. The reflexes evoked at older ages did not present differences between control and malnourished rats. In conclusion, rats submitted to neonatal malnutrition present long-term alteration in reflex latency and nervous conduction velocity. Neonatal malnutrition also alters the reflex excitability at weaning but, since the rat were submitted to a normal diet after weaning, a normal reflex excitability was rapidly recovered which indicates a remarkable plasticity of the reflex pathway.

Absence of linear correlation between fluctuations in area of simultaneous recorded monosynaptic responses and Hoffmann's reflexes in the rat.

In this study we analyze the possible relationship between fluctuations in area of monosynaptic reflex responses (MSR) and Hoffmann's reflex (H reflexes) in the plantar closed loop pathway of the anesthetized rat. These reflexes were evoked by low-frequency stimuli applied to the sciatic nerve or lateral plantar nerve and then concurrently recorded on the distal tibial nerve or lateral plantar nerve, respectively as well as the lateral plantar muscles in the foot of the anesthetized rat. From trial to trial, H reflexes showed higher variability in area than MSR, whether the latter was recorded in the distal tibial nerve (n=8 experiments) or in the lateral plantar nerve (n=5 experiments). No linear correlation was found between changes in area of concurrently evoked MSR and H reflexes (r(MSR-H,n=8)=0.11+/-0.03 and r(MSR-H,n=5)=0.08+/-0.09, respectively). These findings suggest that trial-to-trial fluctuations in area of H reflexes may involve interaction of several sources of variation, among others to MSR variability (due to pre-, and post-synaptic factors influencing the excitability of spinal motoneurons) in combination with those related to peripheral mechanisms, such as trial to trial activation of a different number of muscle fibers, either by the probabilistic transmitter release from neuromuscular junctions, by activation of motor units of variable size or to fluctuations in excitability of muscle fibers.

Immature developmental pattern of the monosynaptic reflex in isolated spinal cord of glial mutant taiep rats.

There is increasing evidence suggesting that glial cells play a crucial role in the formation and maturation of neural circuits. However, little is known about the effects of glial alterations on the establishment of functional circuitry in vivo during the development. The taiep rat, a long-lived neurological mutant characterized by early astrogliosis and demyelination affecting selectively the CNS, provides an interesting model to study the glia-neuron interaction in situ. In the present study, we evaluated the functional development of segmental neural circuits recording the monosynaptic reflex responses (MSR) in the isolated spinal cord of neonatal taiep rats. To evaluate the developmental changes during the first two postnatal weeks, we measured the latency of MSR, the magnitude of depression to paired pulses and the time course of post-tetanic recovery. During the early postnatal period, the MSR of control rats reduced their latency and decreased their sensitivity to depression, as a function of age. By contrast, the MSR of taiep rats failed to develop further from neonatal stage. Near the end of the second postnatal week, the MSR latencies were still prolonged, and the MSR showed a significantly stronger paired pulse depression, and higher post-tetanic recovery times than the age-matched controls. The lack of MSR maturation in taiep rats suggests an early alteration of functional mechanisms underlying the maturation of the spinal reflexes, probably due to the characteristic glial dysfunction(s) of this mutant.

Selectivity of the central control of sensory information in the mammalian spinal cord.

Afferent feedback from muscle proprioceptors, as well as movement-induced activation of skin receptors plays an important role in the patterning of motor activity for stepping and postural control. An important component in this control is the presynaptic GABAergic modulation of the synaptic effectiveness of muscle and cutaneous afferents, known to change in phase with the locomotor cycle, during the execution of voluntary movements, or after a peripheral nerve injury. Recent electrophysiological studies, together with ultrastructural observations, indicate that the distribution of GABAa synapses in the intraspinal arborizations of muscle spindle and tendon organ afferents is not homogeneous. Namely, that some collaterals are the targets of one, or more, GABAergic interneurones, while other collaterals of the same fibre receive no GABAergic connections. In addition, both PAD and inhibition of PAD have a local character. This allows, at least in principle, decoupling the information arising from common sensory inputs. A spatially restricted modulation of PAD could play a significant role in the adjustment of the synaptic effectiveness of Ia afferents at the onset of voluntary contractions in humans, during movement-induced stimulation of the skin, or during the compensation of motor activity following partial denervation of muscles. Changes in the synchronization of the PAD-mediating interneurones can also have a profound effect on the information transmitted by a given set of afferent fibres. Data are presented that in the anesthetized cat, variation in the spontaneous activity of a population of dorsal horn neurones in laminae III-VI, that respond to stimulation of low-threshold cutaneous afferents, produce correlated fluctuations of monosynaptic reflexes by means of pre- and postsynaptic mechanisms. It is suggested that correlated changes in the level of PAD can also play a significant role in the presynaptic adjustment of the synaptic effectiveness of the afferent fibres during specific motor tasks.

[Neurophysiological diagnosis of lumbosacral radicular compression syndrome from late responses]. / Diagnóstico neurofisiológico del síndrome compresivo radicular lumbosacro a través de las respuestas tardías.

INTRODUCTION: Lumbosacral radicular compression syndrome is a disorder that can affect anyone at some moment in their lives, regardless of their sex, age and profession. It appears more frequently in specific groups of people. Late responses constitute neurophysiological studies that allow evaluation of the functional state of the proximal portions of the peripheral nervous system, which are affected to a greater or lesser extent in the course of this pathological state. AIMS. To determine the usefulness of the F wave and H reflex in lumbosacral compressive radiculopathies at L5 and S1. PATIENTS AND METHODS: We examined 100 patients who had been clinically and imagenologically diagnosed as suffering from lumbosacral compressive radiculopathy, which was classified as being L5 and S1. Late responses (F wave and H reflex) were performed and they were compared with a group made up of 74 normal subjects. RESULTS: In patients with L5 radiculopathy, the F wave was abnormal in 66.6% of the cases, where a reduction in the percentage of waves obtained from patients and prolonged minimum, average and maximum latencies predominated. In the case of patients with S1 lumbosacral compressive radiculopathies, 77.5% presented H reflex alterations and the main abnormalities were detected as being the prolongation of reduced amplitude latencies and the absence of response. CONCLUSIONS: The F wave and H reflex are useful tools for evaluating patients with compressive radiculopathies at L5 and S1, respectively.

Anatomical and physiological characteristics of perineal muscles in the female rabbit.

Little information is available on the participation of the perineal striated muscles in female reproductive processes. Here, we describe the gross anatomy and innervation of two striated perineal muscles in the female rabbit, the bulbospongiosus (BSM) and ischiocavernosus (ISM), and analyze their reflex electromyographic (EMG) activity in response to stimulation of the perigenital skin and vaginal tract. Twenty-four mature chinchilla-breed rabbit does were used: 12 to describe the anatomy and innervation of the muscles, 9 to determine reflex EMG activity of the muscles in response to stimulation of the perigenital skin and specific levels of the vaginal tract and 3 to analyze the effect of contraction of the muscles on intravaginal pressure. Both muscles were well developed, with their fibers originating at the ischiadic arch and inserting onto the ligamentum suspensorium clitoridis. Branches of the clitoral and perineal nerves innervated the BSM and ISM, respectively. Bilateral electrical stimulation of these nerves provoked retraction of the clitoral sheath and an increase in intravaginal pressure at the level of the perineal vagina. Whereas neither muscle responded to stimulation of the perigenital skin, both were reflexively activated during mechanical stimulation of the inner walls of the perineal vagina. Prolonged cervical stimulation inhibited this reflex. Thus, in reproductive processes such as copulation and/or parturition, the contraction of these muscles may be induced during stimulation of the perineal vagina.

The effects of calcium channel blocker, flunarizine on spinal reflexes in the cats.

Effects of calcium channel blocker flunarizine on spinal monosynaptic reflexes were investigated in spinal cats. Flunarizine was administered locally into the spinal cord (10, 50, 100 microM) and intraperitoneally (5, 10, 20 mg/kg). Adult cats (n = 10), weighing 1.5-3 kg were anesthetized with ketamine (50 mg/kg, i.m.) and artificially ventilated. Animals were spinalized at C1 level. A laminectomy was performed in the lumbosacral region. The ventral and dorsal roots of segment L5 were isolated and a pouch of skin was formed at the site of the dissection to allow the exposed tissues to be covered with liquid paraffin. The temperature was kept at 38.5 degrees C with a heating pad. A polyethylene cannula was introduced into the left carotid artery to monitor blood pressure, which was kept above 100 mmHg. The dorsal root of segment L5 was placed on a silver-silver chloride wire electrode for stimulation through an isolation unit. The reflex potentials were recorded from the ipsilateral L5 ventral root, mounted on a silver-silver chloride wire electrode. The systemic (5, 10, 20 mg/kg) and local (50 and 100 microM) dosages of cinnarizin derivative flunarizine significantly decreased the amplitude of reflex response (p < 0.05). Moreover, the latency of the monosynaptic reflexes was increased after administration of the drug (p < 0.05). Voltage-dependent calcium channels in the spinal cord may play an important role to regulate reflex respond.

Spinal reflex activity in patients with Duchenne, limb-girdle and myotonic muscular dystrophies

La actividad refleja espinal excitatoria e inhibitoria fue estudiada en pacientes con distrofia muscular del tipo Duchenne, de las cinturas y miotónica. Para ello se emplearon técnicas electrofisiológicas que permitieron conocer el comportamiento de las respuestas H y T y del período silente. A esto se sumó la investigación del coeficiente de excitabilidad de la motoneurona espinal alfa. Tanto en la forma de Duchenne como en la de las cinturas el comportamiento reflejo medular, medido a través de las respuestas H y T, sugirió el compromiso de la neurona motora alpha del asta anterior de médula. En los que padecían la forma miotónica, las mismas respuestas se mostraron igualmente alteradas; sin embargo, en este caso, las peculiaridades del comportamiento observado están, más probablemente, ligadas a la modificación anatómica que exhibe el huso neuromuscular en estos pacientes antes que con una lesión primaria de motoneurona. En los tres grupos el coeficiente de excitabilidad estuvo reducido, fundamentalmente en las formas de Duchenne y miotónica. Este hallazgo señala una cierta participación de la corteza cerebral motora en estas enfermedades. No se encontraron diferencias entre controles y probandos en relación al período silente, hecho que sugiró la indemnidad de los circuitos medulares inhibitorios en estos pacientes

Spinal reflex activity in patients with Duchenne, limb-girdle and myotonic muscular dystrophies

La actividad refleja espinal excitatoria e inhibitoria fue estudiada en pacientes con distrofia muscular del tipo Duchenne, de las cinturas y miotónica. Para ello se emplearon técnicas electrofisiológicas que permitieron conocer el comportamiento de las respuestas H y T y del período silente. A esto se sumó la investigación del coeficiente de excitabilidad de la motoneurona espinal alfa. Tanto en la forma de Duchenne como en la de las cinturas el comportamiento reflejo medular, medido a través de las respuestas H y T, sugirió el compromiso de la neurona motora alpha del asta anterior de médula. En los que padecían la forma miotónica, las mismas respuestas se mostraron igualmente alteradas; sin embargo, en este caso, las peculiaridades del comportamiento observado están, más probablemente, ligadas a la modificación anatómica que exhibe el huso neuromuscular en estos pacientes antes que con una lesión primaria de motoneurona. En los tres grupos el coeficiente de excitabilidad estuvo reducido, fundamentalmente en las formas de Duchenne y miotónica. Este hallazgo señala una cierta participación de la corteza cerebral motora en estas enfermedades. No se encontraron diferencias entre controles y probandos en relación al período silente, hecho que sugiró la indemnidad de los circuitos medulares inhibitorios en estos pacientes (AU)

Neurofisiología / Neurophysiology

Fisiología del sistema nervioso. Describe la anatomia y funciones de las vias nerviosas aferentes y eferentes del sistema nervioso central y perisferico, del sistema nervioso autónomo y de los diferentes sentidos. Explica la fisiología del comportamiento,las emociones y del equilibrio postural

Neurofisiología / Neurophysiology

Fisiología del sistema nervioso. Describe la anatomia y funciones de las vias nerviosas aferentes y eferentes del sistema nervioso central y perisferico, del sistema nervioso autónomo y de los diferentes sentidos. Explica la fisiología del comportamiento,las emociones y del equilibrio postural