Cardiac reflexes and their neural pathways in lepidopterous insects

Previously described salines for lepidoptera did not maintain a constant heart rate for a very long. We have been successful in maintaining a normal heartbeat for many hours in a newly designed saline. This saline was also suitable for maintaining normal neuromuscular junctional potentials. The cardiac reflexes studied in larvae of Bombyx and Agrius were five types of cardiac responses induced by mechanical stimuli to sensillar setae. The cardiac responses were caused by electrical stimulation of nerves in the reflex pathways. The antidromic heartbeat was triggered even in larvae before the 5th instar by stimulation of axons in the visceral nerve arising from the frontal ganglion and terminating at the aorta, while spontaneous heartbeat reversal started to occur in wandering larvae. Other axons in the visceral nerve terminate at the rear end of the heart. Electrical stimuli to the nerves caused cardiac inhibition of the orthodromic heartbeat. Nerves extending from the visceral nerve to the alary muscles of the 2nd abdominal segment contain axons to increase the tone of the muscles. Nerves extending from the 7th abdominal ganglion to the most posterior alary muscles also contain axons to increase the tone of the muscles, and were responsible for acceleration of the antidromic and orthodromic heartbeat, respectively.     

Cruciate ligament reflexes.

The idea of muscular reflexes elicited from sensory nerves of the cruciate ligaments is more than 100 years old, but the existence of such reflexes has not been proven until the recent two decades. First in animal experiments, a muscular excitation could be elicited in the hamstrings when the anterior cruciate ligament (ACL) was pulled, and tension in the ligament caused activity of the gamma motor neurones of the muscles around the knee. Impulses from the sensory nerves in ACL were activated during motion of the knee, in particular overstretching and combined extension and rotation. In humans, proprioception in the knee is decreased after ACL rupture. By mechanical or electrical stimulation of the ACL, an excitation in the hamstrings muscles can be elicited. During muscular activity, stimulation of the ACL or PCL results in a clear inhibition of the ongoing activity, both during static isometric and isokinetic muscle work, and also during dynamic activity (gait). This inhibitory reflex subjectively resembled giving way. The latency of the reflex was short in animals (about 3 ms) and long in humans (60-120 ms), probably caused by differences in the experimental setup and between species. The long latency in humans makes it unlikely that it is a directly protective reflex. Instead it may be involved in the updating of motor programs. Further research may characterize the reflex in details and map its pathways. The existence of this reflex indicate that the cruciate ligaments have an afferent function, which influences knee dynamics.     

Electrophysiological evaluation of the intensity of protective respiratory reflexes

The impulse activity of bulbar respiratory neurons and the electrical activity of main respiratory muscles were studied stereotaxically and electromyographically on 21 male and female cats anesthetized with pentobarbital (40 mg/kg, i.p.) during defensive respiratory (expiratory and coughing) reflexes. During stimulation of laryngopharyngeal and tracheobronchial receptors, a pronounced focus of excitation appears in the bulbar respiratory centre, its peripheral manifestation being powerful electrical activity of expiratory muscles (expiratory reflex) or of both expiratory and inspiratory muscles (coughing). Respiratory defensive reflexes are very powerful and stable and are retained in hypercapnia and hypoxia.     

Wide-pulse-width, high-frequency neuromuscular stimulation: implications for functional electrical stimulation.

Electrical stimulation (1-ms pulses, 100 Hz) produces more torque than expected from motor axon activation (extra contractions). This experiment investigates the most effective method of delivering this stimulation for neuromuscular electrical stimulation. Surface stimulation (1-ms pulses; 20 Hz for 2 s, 100 Hz for 2 s, 20 Hz for 3 s) was delivered to triceps surae and wrist flexors (muscle stimulation) and to median and tibial nerves (nerve stimulation) at two intensities. Contractions were evaluated for amplitude, consistency, and stability. Surface electromyograph was collected to assess how H-reflexes and M-waves contribute. In the triceps surae, muscle stimulation produced the largest absolute contractions (23% maximal voluntary contraction), evoked the largest extra contractions as torque increased by 412% after the 100-Hz stimulation, and was more consistent and stable compared with tibial nerve stimulation. Absolute and extra contraction amplitude, consistency, and stability of evoked wrist flexor torques were similar between stimulation types: torques reached 11% maximal voluntary contraction, and extra contractions increased torque by 161%. Extra contractions were 10 times larger in plantar flexors compared with wrist flexors with muscle stimulation but were similar with nerve stimulation. For triceps surae, H reflexes were 3.4 times larger than M waves during nerve stimulation, yet M waves were 15 times larger than H reflexes during muscle stimulation. M waves in the wrist flexors were larger than H reflexes during nerve (8.5 times) and muscle (18.5 times) stimulation. This is an initial step toward utilizing extra contractions for neuromuscular electrical stimulation and the first to demonstrate their presence in the wrist flexors.     

Effects of peripheral inputs from hindlimb on the monosynaptic reflex of motoneurons innervating tail muscles.

The effects of group II muscle (PBSt, GS) and cutaneous afferent (Sur, SPc, Tib) inputs from the hindlimb on the monosynaptic reflexes of motoneurons innervating tail muscles were studied in lower spinalized cats. Stimulation of the cutaneous nerves at the conditioning-test stimulus interval of about 10-20 ms facilitated and inhibited the monosynaptic reflexes of ipsilateral and contralateral tail muscles, respectively. The effects of the muscle nerve stimulation were not so prominent as those elicited by cutaneous nerve stimulation. The monosynaptic reflex was also inhibited by muscle nerve stimulation at 10-50 ms intervals. The effects of conditioning stimulation of the hindlimb peripheral nerves at short intervals were depressed or blocked by section of the ipsilateral lateral funiculus at S1 spinal segment. These findings show that the neuronal pathway from hindlimb afferents to tail muscle motoneurons passed the lateral funiculus of the spinal cord and modulates the motoneuronal activity of tail muscles.     

Reflex control of posterior shoulder muscles from arm afferents in healthy people

In order to position the hand during functional tasks, control of the shoulder is required. Heteronymous reflexes from the upper limb to shoulder muscles are used to assist in this control. To investigate this further, the radial and ulnar nerves were stimulated at elbow level whilst surface electromyographic activity of posterior deltoid, infraspinatus and latissimus dorsi muscles were recorded. In addition, the cutaneous branch of the radial nerve and the skin of the fifth digit were stimulated in order to investigate any cutaneous contribution to reflex activity. Reflexes were evoked in all three of these shoulder muscles from hand and/or forearm afferents. However, the reflexes differed; whereas both excitatory and inhibitory reflexes were evoked in posterior deltoid and infraspinatus, the reflexes in latissimus dorsi were mainly excitatory. Cutaneomuscular reflexes were seldom evoked here, but when they were present they were generally evoked at longer latencies than the reflexes evoked by mixed nerve stimulation. The results suggest a role for reflexes originating from the forearm and/or hand in the control of the shoulder.     

Interlimb Reflexes Induced by Electrical Stimulation of Cutaneous Nerves after Spinal Cord Injury

Whether interlimb reflexes emerge only after a severe insult to the human spinal cord is controversial. Here the aim was to examine interlimb reflexes at rest in participants with chronic (>1 year) spinal cord injury (SCI, n = 17) and able-bodied control participants (n = 5). Cutaneous reflexes were evoked by delivering up to 30 trains of stimuli to either the superficial peroneal nerve on the dorsum of the foot or the radial nerve at the wrist (5 pulses, 300 Hz, approximately every 30 s). Participants were instructed to relax the test muscles prior to the delivery of the stimuli. Electromyographic activity was recorded bilaterally in proximal and distal arm and leg muscles. Superficial peroneal nerve stimulation evoked interlimb reflexes in ipsilateral and contralateral arm and contralateral leg muscles of SCI and control participants. Radial nerve stimulation evoked interlimb reflexes in the ipsilateral leg and contralateral arm muscles of control and SCI participants but only contralateral leg muscles of control participants. Interlimb reflexes evoked by superficial peroneal nerve stimulation were longer in latency and duration, and larger in magnitude in SCI participants. Interlimb reflex properties were similar for both SCI and control groups for radial nerve stimulation. Ascending interlimb reflexes tended to occur with a higher incidence in participants with SCI, while descending interlimb reflexes occurred with a higher incidence in able-bodied participants. However, the overall incidence of interlimb reflexes in SCI and neurologically intact participants was similar which suggests that the neural circuitry underlying these reflexes does not necessarily develop after central nervous system injury.     

Laryngeal motor control in frogs: Role of vagal and laryngeal feedback

Using decerebrate frogs (Rana catesbeiana), we investigated the role of vagal and laryngeal sensory feedback in controlling motor activation of the larynx. Vagal and laryngeal nerve afferents were activated by electrical stimulation of the intact vagal and laryngeal nerves. Pulmonary afferents were activated by lung inflation. Reflex responses were recorded by measuring efferent activity in the laryngeal branch of the vagus (Xℓ) and changes in glottal aperture. Two glottic closure reflexes were identified, one evoked by lung inflation or electrical stimulation of the main branch of the vagus (Xm), and the other by electrical stimulation of Xℓ. Lung inflation evoked a decrementing burst of Xℓ efferent activity and electrical stimulation of Xm resulted in a brief burst of Xℓ action potentials. Electrical stimulation of Xℓ evoked a triphasic mechanical response, an abrupt glottal constriction followed by glottal dilatation followed by a long-lasting glottal constriction. The first phase was inferred to be a direct (nonreflex) response to the stimulus, whereas the second and third represent reflex responses to the activation of laryngeal afferents. Intracellular recordings of membrane potential of vagal motoneurons of lung and nonlung types revealed EPSPs in both types of neurons evoked by stimulation of Xm or Xℓ, indicating activation of glottal dilator and constrictor motoneurons. In summary, we have identified two novel reflexes producing glottic closure, one stimulated by activation of pulmonary receptors and the other by laryngeal receptors. The former may be part of an inspiratory terminating reflex and the latter may represent an airway protective reflex. © 1997 John Wiley & Sons, Inc. J Neurobiol 33: 213–222, 1997     

Interaction between depressor and pressor reflexes arising from the aorta in dogs

In 18 dogs anesthetized with morphine-chloralose the interaction between the aortic nerve (AN) pressor and depressor reflexes was studied. Low-intensity, high-frequency electrical stimulation of the AN causes large decreases in heart rate and systemic pressure characteristic of baroreflex responses. High-intensity, low-frequency stimulation of the AN causes modest increases in heart rate and systemic pressure similar to the responses observed to intraaortic nicotine. Simultaneous electrical stimulation of these antagonistic reflexes results in much smaller (P less than 0.001) reductions in heart rate and systemic pressure that can be explained on the basis of simple addition of the individual responses. Similarly the AN depressor reflexes are suppressed during intraaortic infusions of nicotine (40 micrograms/min). The results suggest that the inhibitory effects of the AN baroreflexes are suppressed by the aortic chemoreflexes . This interaction occurs in the CNS rather than at the level of the heart or vascular smooth muscle.     

Enhancement of peripheral nerve regeneration due to treadmill training and electrical stimulation is dependent on androgen receptor signaling

Moderate exercise in the form of treadmill training and brief electrical nerve stimulation both enhance axon regeneration after peripheral nerve injury. Different regimens of exercise are required to enhance axon regeneration in male and female mice (Wood et al.: Dev Neurobiol 72 (2012) 688–698), and androgens are suspected to be involved. We treated mice with the androgen receptor blocker, flutamide, during either exercise or electrical stimulation, to evaluate the role of androgen receptor signaling in these activity‐based methods of enhancing axon regeneration. The common fibular (CF) and tibial (TIB) nerves of thy‐1‐YFP‐H mice, in which axons in peripheral nerves are marked by yellow fluorescent protein (YFP), were transected and repaired using CF and TIB nerve grafts harvested from non‐fluorescent donor mice. Silastic capsules filled with flutamide were implanted subcutaneously to release the drug continuously. Exercised mice were treadmill trained 5 days/week for 2 weeks, starting on the third day post‐transection. For electrical stimulation, the sciatic nerve was stimulated continuously for 1 h prior to nerve transection. After 2 weeks, lengths of YFP+ profiles of regenerating axons were measured from harvested nerves. Both exercise and electrical stimulation enhanced axon regeneration, but this enhancement was blocked completely by flutamide treatments. Signaling through androgen receptors is necessary for the enhancing effects of treadmill exercise or electrical stimulation on axon regeneration in cut peripheral nerves. © 2013 Wiley Periodicals, Inc. Develop Neurobiol 74: 531–540, 2014     

A systematic method to quantify the presence of cross-talk in stimulus-evoked EMG responses: implications for TMS studies

Surface electromyography (EMG) responses to noninvasive nerve and brain stimulation are routinely used to provide insight into neural function in humans. However, this could lead to erroneous conclusions if evoked EMG responses contain significant contributions from neighboring muscles (i.e., due to "cross-talk"). We addressed this issue with a simple nerve stimulation method to provide quantitative information regarding the size of EMG cross-talk between muscles of the forearm and hand. Peak to peak amplitude of EMG responses to electrical stimulation of the radial, median, and ulnar nerves (i.e., M-waves) were plotted against stimulation intensity for four wrist muscles and two hand muscles (n = 12). Since electrical stimulation can selectively activate specific groups of muscles, the method can differentiate between evoked EMG arising from target muscles and EMG cross-talk arising from nontarget muscles. Intramuscular EMG responses to nerve stimulation and root mean square EMG produced during maximal voluntary contractions (MVC) of the wrist were recorded for comparison. Cross-talk was present in evoked surface EMG responses recorded from all nontarget wrist (5.05-39.38% Mmax) and hand muscles (1.50-24.25% Mmax) and to a lesser degree in intramuscular EMG signals (～3.7% Mmax). The degree of cross-talk was comparable for stimulus-evoked responses and voluntary activity recorded during MVC. Since cross-talk can make a considerable contribution to EMG responses in forearm and hand muscles, care is required to avoid misinterpretation of EMG data. The multiple nerve stimulation method described here can be used to quantify the potential contribution of EMG cross-talk in transcranial magnetic stimulation and reflex studies.     

盆底电刺激对大鼠盆底肌肌肉、神经发育的形态学影响研究

目的:探讨与研究盆底电刺激对大鼠盆底肌肌肉、神经发育的形态学影响.方法:36只Wistar产后健康雌性大鼠分为对照组、模型组与刺激组,每组12只.模型组与刺激组都建立了压力性尿失禁模型,对照组不给予任何处理.建模后刺激组给予盆底电刺激,每3 d一次,持续治疗12d;模型组在建模后不给予任何治疗处理.结果:模型组与刺激组...     

Inspiratory and expiratory patterns of the pectoralis major muscle during pulmonary defensive reflexes

Experiments wereconducted to determine the discharge pattern of the pectoralis majormuscle during pulmonary defensive reflexes in anesthetized cats(n = 15). Coughs andexpiration reflexes were elicited by mechanical stimulation of theintrathoracic trachea or larynx. Augmented breaths occurredspontaneously or were evoked by the same mechanical stimuli.Electromyograms (EMGs) were recorded from the diaphragm, rectusabdominis, and pectoralis major muscles. During augmented breaths, thepectoralis major had inspiratory EMG activity similar to that of thediaphragm, but during expiration reflexes the pectoralis major also hadpurely expiratory EMG activity similar to the rectus abdominis. Duringtracheobronchial cough, the pectoralis major had an inspiratory patternsimilar to that of the diaphragm in 10 animals, an expiratory patternsimilar to that of the rectus abdominis in 3 animals, and a biphasicpattern in 2 animals. The pectoralis major was active during both the inspiratory and expiratory phases during laryngeal cough. We conclude that, in contrast to the diaphragm or rectus abdominis muscles, thepectoralis major is active during both inspiratory and expiratory pulmonary defensive reflexes.

     

Intraoperative monitoring of the abducens nerve in extended endonasal endoscopic approach: A pilot study technical report

BackgroundTo determine the reliability and usefulness of intraoperative monitoring of the abducens nerve during extended endonasal endoscopic skull base tumor resection.MethodsWe performed abducens nerve intraoperative monitoring in 8 patients with giant clival lesions recording with needle electrodes sutured directly into the lateral rectus muscles of the eye to evaluate spontaneous electromyographic activity and triggered responses following stimulation of the abducens nerves.ResultsA total of 16 abducens nerves were successfully recorded during endoscopic endonasal skull base surgeries. Neurotonic discharges were seen in two patients (12% [2/16] abducens nerves). Compound muscle action potentials of the abducens nerves were evoked with 0.1–4 mA and maintained without changes during the neurosurgical procedures. No patient had new neurological deficits or ophthalmological complications post-surgery.ConclusionsIntraoperative monitoring of the abducens nerve during the extended endonasal endoscopic approach to skull base tumors appears to be a safe method with the potential to prevent neural injury through the evaluation of neurotonic discharges and triggered responses.     

Modulation of heart activity during withdrawal reflexes in the snail <Emphasis Type="Italic">Helix aspersa</Emphasis>

The beating activity of the molluscan heart is myogenic, but it is influenced by nervous signals of central origin. Previous studies have demonstrated changes in cardiac output during feeding and other behaviors. Here, we describe a short latency, transient cardiac response that accompanies withdrawal reflexes. When evoked by electrical stimulation of peripheral nerves, the response was detected within one or two heartbeats. Beat amplitudes increased on average 11.6%, and inter-beat intervals decreased on average 2.1%. The mean duration of the response was 28.1 s. A transient inhibitory phase often preceded the excitatory response. Results from testing various nerves and tissues show that the cardiac responses invariably occur whenever contractions of the tentacle retractor muscle are elicited. Even stimulation of the ovotestis and the kidney elicit responses despite their protected locations within the mantle cavity. Three excitatory cardioactive neurons are identified in the central nervous system of Helix aspersa, and their involvement in the reflex response is documented. The results suggest that the heart output is initially inhibited to relax the hydroskeleton and thereby aid withdrawal movements. A delayed increase in cardiac output then facilitates the re-inflation, hence eversion, of the withdrawn body parts.     

EFFECT OF CYANIDE AND ELECTRICAL STIMULATION ON PHOSPHOINOSITIDE METABOLISM IN LOBSTER NERVES

The contents of phosphoinositides, ATP, glucose and lactate in leg and claw nerves of the lobster were determined. Nerves were also analysed after cyanide poisoning, after electrical stimulation, and 1 h after removing the leg from the lobster. Cyanide poisoning decreased the levels of ATP and glucose and increased the content of lactate but did not alter the levels of phosphoinositides. Nerves left in situ for 1 h after disconnection from the central nervous system exhibited a decrease in the content of tri-phosphoinositides (TPI) of 50 per cent, without changes in ATP, glucose or lactate. The TPI change was reversed after incubation for 1 h in oxygenated seawater. Nerves labelled in vivo with ³²P were removed and stimulated at 50 Hz for 5 min. The turnover of TPI phosphorus increased on stimulation in both normal and cyanide-poisoned nerves. In contrast, turnover of ATP increased after stimulation in normal nerves but not in cyanide-treated nerves. We sought to determine whether polyphosphoinositides play a greater role in resting metabolism of the nerve or in the conducting mechanisms. Our results make more likely the involvement of TPI in permeability changes of neural membranes during excitation.     

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.     

MRI study of pharyngeal airway changes during stimulation of the hypoglossal nerve branches in rats.

The medial branch (Med) of the hypoglossal nerve innervates the tongue protrudor muscles, whereas the lateral branch (Lat) innervates tongue retractor muscles. Our previous finding that pharyngeal airflow increased during either selective Med stimulation or whole hypoglossal nerve (WHL) stimulation (coactivation of protrudor and retractor muscles) led us to examine how WHL, Med, or Lat stimulation affected tongue movements and nasopharyngeal (NP) and oropharyngeal (OP) airway volume. Electrical stimulation of either WHL, Med, or Lat nerves was performed in anesthetized, tracheotomized rats while magnetic resonance images of the NP and OP were acquired (slice thickness 0.5 mm, in-plane resolution 0.25 mm). NP and OP volume was greater during WHL and Med stimulation vs. no stimulation (P < 0.05). Ventral tongue depression (measured in the midsagittal images) and OP volume were greater during Med stimulation than during WHL stimulation (P < 0.05). Lat stimulation did not alter NP volume (P = 0.39). Our finding that either WHL or Med stimulation dilates the NP and OP airways sheds new light on the control of pharyngeal airway caliber by extrinsic tongue muscles and may lead to new treatments for patients with obstructive sleep apnea.     

Convergence in Reflex Pathways from Multiple Cutaneous Nerves Innervating the Foot Depends upon the Number of Rhythmically Active Limbs during Locomotion

Neural output from the locomotor system for each arm and leg influences the spinal motoneuronal pools directly and indirectly through interneuronal (IN) reflex networks. While well documented in other species, less is known about the functions and features of convergence in common IN reflex system from cutaneous afferents innervating different foot regions during remote arm and leg movement in humans. The purpose of the present study was to use spatial facilitation to examine possible convergence in common reflex pathways during rhythmic locomotor limb movements. Cutaneous reflexes were evoked in ipsilateral tibialis anterior muscle by stimulating (in random order) the sural nerve (SUR), the distal tibial nerve (TIB), and combined simultaneous stimulation of both nerves (TIB&SUR). Reflexes were evoked while participants performed rhythmic stepping and arm swinging movement with both arms and the leg contralateral to stimulation (ARM&LEG), with just arm movement (ARM) and with just contralateral leg movement (LEG). Stimulation intensities were just below threshold for evoking early latency (<80 ms to peak) reflexes. For each stimulus condition, rectified EMG signals were averaged while participants held static contractions in the stationary (stimulated) leg. During ARM&LEG movement, amplitudes of cutaneous reflexes evoked by combined TIB&SUR stimulation were significantly larger than simple mathematical summation of the amplitudes evoked by SUR or TIB alone. Interestingly, this extra facilitation seen during combined nerve stimulation was significantly reduced when performing ARM or LEG compared to ARM&LEG. We conclude that locomotor rhythmic limb movement induces excitation of common IN reflex pathways from cutaneous afferents innervating different foot regions. Importantly, activity in this pathway is most facilitated during ARM&LEG movement. These results suggest that transmission in IN reflex pathways is weighted according to the number of limbs directly engaged in human locomotor activity and underscores the importance of arm swing to support neuronal excitability in leg muscles.     

Clasper control in the round stingray,Urolapkus halleri lower sensor motor pathways

Synopsis The innervation of the clasper has been studied in the round stingray,Urolophus halleri. Several large myelinated nerves (diameters approx. 0.7 mm; # 60–64 counting from the vagus) innervate the clasper muscles and skin. Low level electrical stimulation (<100A) of the nerves evokes clasper movements including: elevation, medial and lateral extension, rotation and opening. Stimulation of the spinal cord in the area of the roots of the clasper nerves also evoked the movements (<100A). Retrograde labeling of the clasper nerves using either cobalt-lysine or horseradish peroxidase (HRP) confirmed that motor neurons and sensory components of the nerves are at the levels indicated by stimulation. The motor neurons have large multipolar cell bodies (50–70) and occupy a discrete segment of the spinal cord.