Comparison of Threshold and Tolerance Nociceptive Withdrawal Reflexes in Horses

The nociceptive withdrawal reflex (NWR) is used to investigate nociception in horses. The NWR threshold is a classical model endpoint. The aims of this study were to determine NWR tolerance and to compare threshold and tolerance reflexes in horses. In 12 horses, the NWR was evoked through electrical stimulation of the digital nerve and recorded via electromyography from the deltoid. Behavioral reactions were scored from 0 to 5 (tolerance). First, the individual NWR threshold was defined, then stimulation intensity was increased to tolerance. The median NWR threshold was 7.0 mA, whereas NWR tolerance was 10.7 mA. Upon visual inspection of the records, two main reflex components R1 (median latency 44 ms) and R2 (median latency 81 ms) were identified at threshold. Increasing stimulation intensity to tolerance led to a significant increase in the amplitude and duration of R1 and R2, whereas their latency decreased. At tolerance, a single burst of early, high-amplitude reflex activity, with a median latency of 39 ms, was detected in 15 out of 23 stimulations (65%). The results of this study suggest that (1) it is feasible to determine NWR tolerance in horses and (2) high-intensity stimuli initiate ultrafast bursts of reflex activity, which is well known in practice and has now been quantified using the NWR model.

Sleep and conditioning of the siphon withdrawal reflex in Aplysia

Sleep is essential for memory consolidation after learning as shown in mammals and invertebrates such as bees and flies. Aplysia californica displays sleep and sleep in this mollusk was also found to support memory for an operant conditioning task. Here, we investigated whether sleep in Aplysia is also required for memory consolidation in a simpler type of learning, i.e., the conditioning of the siphon withdrawal reflex. Two groups of animals (Wake, Sleep, each n=11) were conditioned on the siphon withdrawal reflex with the training following a classical conditioning procedure where an electrical tail shock served as unconditioned stimulus (US) and a tactile stimulus to the siphon as conditioned stimulus (CS). Responses to the CS were tested before (Pre-test), 24 and 48 hours after training. While Wake animals remained awake for 6 hours after training, Sleep animals had undisturbed sleep. The 24h-test in both groups was combined with extinction training, i.e., the extended presentation of the CS alone over two blocks. At the 24h-test, siphon withdrawal durations to the CS were distinctly enhanced in both Sleep and Wake groups with no significant difference between groups, consistent with the view that consolidation of a simple conditioned reflex response does not require post-training sleep. Surprisingly, extinction training did not reverse the enhancement of responses to the CS. On the contrary, at the 48h-test, withdrawal durations to the CS were even further enhanced across both groups. This suggests that processes of sensitization, an even simpler non-associative type of learning, contributed to the withdrawal responses. Our study provides evidence for the hypothesis that sleep preferentially benefits consolidation of more complex learning paradigms than conditioning of simple reflexes.

Tempo-spatial integration of nociceptive stimuli assessed via the nociceptive withdrawal reflex in healthy humans.

Spatial information of nociceptive stimuli applied in the skin of healthy humans is integrated in the spinal cord to determine the appropriate withdrawal reflex response. Double-simultaneous stimulus applied in different skin sites are integrated, eliciting a larger reflex response. The temporal characteristics of the stimuli also modulate the reflex e.g. by temporal summation. The primary aim of this study was to investigate how the combined tempo-spatial aspects of two stimuli are integrated in the nociceptive system. This was investigated by delivering single and double simultaneous stimulation, and sequential stimulation with different inter-stimulus intervals (ISIs ranging 30-500 ms.) to the sole of the foot of fifteen healthy subjects. The primary outcome measure was the size of the nociceptive withdrawal reflex (NWR) recorded from the Tibialis Anterior (TA) and Biceps Femoris (BF) muscles. Pain intensity was measured using an NRS scale. Results showed spatial summation in both TA and BF when delivering simultaneous stimulation. Simultaneous stimulation provoked larger reflexes than sequential stimulation in TA, but not in BF. Larger ISIs elicited significantly larger reflexes in TA, while the opposite pattern occurred in BF. This differential modulation between proximal and distal muscles suggests the presence of spinal circuits eliciting a functional reflex response based on the specific tempo-spatial characteristics of a noxious stimulus. No modulation was observed in pain intensity ratings across ISIs. Absence of modulation in the pain intensity ratings argues for an integrative mechanism located within the spinal cord governed by a need for efficient withdrawal from a potentially harmful stimulus.

Effect of Sedation on the Neurological Examination of the Patellar and Withdrawal Reflexes in Healthy Dogs

Introduction: Pain, temperament, fear, and anxiety can prevent safe and accurate evaluation of common neurologic reflexes in dogs. When sedation is used it is unknown how the neurological examination, and specifically patellar and withdrawal reflexes are affected, and, if present, how long any effect might last. The purpose of this study is to investigate the effect of sedation on the evaluation of select common limb spinal reflexes in healthy dogs.Material and Methods: Fourteen healthy dogs with normal neurologic exams were included. After placing joint landmarks, patellar reflex and pelvic and thoracic limb withdrawal reflexes were tested. Joint angles were measured, obtaining reflex angle endpoints, change in angle, and change in time to reflex completion. These measurements were recorded at different time points: prior to sedation (awake timepoint), 15 and 30 min following administration of standardized sedation protocol of dexmedetomidine and butorphanol, and 15 and 30 min following administration of a standardized reversal agent, atipamazole.Results: For patellar reflex, the stifle end angle increased from 91.5 to 108.55 degrees (p < 0.0001) 15 min following sedation, and remained increased at 104.5 degrees (p < 0.0001) 30 min following sedation. Stifle change in angle increased from 9.6 to 24.4 degrees (p < 0.0001) 15 min following sedation, and remained increased at 20.85 degrees (p < 0.0001) and 11 degrees (p = 0.012) at 30 min sedation and 15 min reversal. Tarsal joint in pelvic withdrawal and elbow in thoracic withdrawal reflexes did not differ in at any timepoint of sedation or reversal when compared with the awake timepoint, for end angle or change in angle. The increases in end angle and change in angle for patellar reflex generated a change in time for patellar reflex from 0.12 s (awake) to 0.129 s (15 min sedation) which was statistically significant (p = 0.041). Change in time did not differ for pelvic withdrawal or thoracic withdrawal.Discussion/Conclusions: Reflexes were elicited in all dogs under sedation. Sedation does not affect the evaluation of the withdrawal reflex on any limb but improves the visualization of the patellar reflex in this group of neurologically normal dogs.

Exploring the Effects of Changping Decoction on Irritable Bowel Syndrome by Pathway and Pharmacology Network Bioinformatics Analysis

Background An increasing body of research has confirmed the effectiveness of Traditional Chinese Medicine (TCM) for the treatment of irritable bowel syndrome (IBS).Methods We explored the potential mechanism of Changping decoction (CPD) in the treatment of IBS through pathway analysis based on a network pharmacology approach. Public databases, including the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform, Gene Expression Omnibus, and STRING, were used to screen the active ingredients and targets of CPD. Enrichment analysis was performed using the R-3.6.0 software to expound the biological functions and related pathways of CPD targets. The Cytoscape software was used to construct a “disease-CPD-target” network and identify hub genes of CPD relevant for the treatment of IBS. Employing rat models, pathological observation and abdominal withdrawal reflex tests were used to verify the effectiveness of CPD in the treatment of IBS. Immunohistochemistry was used to confirm the relationship between the CPD treatment and hub genes.Results Network pharmacological analysis of CPD for the treatment of IBS identified 159 active ingredients. A total of 118 key targets were identified, including MAPK8, VEGFA, PTGS2, and others. A series of signaling pathways, such as MAPK, Kaposi sarcoma-associated herpesvirus infection, and IL-17 signaling pathway were found to play an important role in the therapeutic mechanism of CPD in the treatment of IBS. Pathological observation and abdominal withdrawal reflex tests confirmed that the symptoms of IBS in rats were relieved by CPD. Moreover, immunohistochemistry confirmed that CPD could inhibit the expression of inflammation-associated factors, such as VEGFA, MAPK8, and PTGS2.Conclusions Based on network pharmacology analysis, the present study provides insights into the potential mechanism of CPD in the treatment of IBS after successfully screening for associated key target genes and signaling pathways. These findings establish a theoretical basis for the development of CPD-derived therapeutics.

Intraperitoneal Alfaxalone and Alfaxalone–Dexmedetomidine Anesthesia in Sprague–Dawley Rats (Rattus norvegicus)

Due to their unpredictability and variable effects, injectable anesthetic regimens in laboratory rodent species warrant refinement. In our study we sought to evaluate alfaxalone, which has gained recent popularity in veterinary medicine, alone and in combination with dexmedetomidine to evaluate their anesthetic ability in Sprague–Dawley rats when administered intraperitoneally. Three doses of alfaxalone only and 4 dose combinations of alfaxalone-dexmedetomidine were tested in males and female rats. The time to induction, anesthetic duration, pulse rate, respiratory rate, temperature, and time to recovery were recorded by a blind observer. The level of anesthesia induced by the various anesthetic protocols was assessed by using pedal withdrawal reflex to a noxious stimulus and scored according to the response. Dependent on the treatment group, atipamezole or saline was administered intraperitoneally once animals reached 60 min of anesthesia. Regardless of the dose, alfaxalone alone achieved only a sedative level of anesthesia, whereas all alfaxalone-dexmedetomidine combinations led to a surgical level of anesthesia in all animals. Anesthesia regimens using alfaxalone alone and in combination with dexmedetomidine demonstrated sex-associated differences, with female rats maintaining longer durations of sedation or anesthesia than their male counterparts. Both male and female rats displayed decreases in physiologic parameters consistent with the effects of dexmedetomidine. Given the results described herein, we recommend 20 mg/kg alfaxalone for sedation and 30 mg/kg alfaxalone combined with 0.05 mg/kg dexmedetomidine for surgical anesthesia in female rats. Appropriate doses of alfaxalone only and alfaxalone-dexmedetomidine for male rats were not determined in this study and need further evaluation.

Evoking the Withdrawal Reflex via Successive Needle-Pricking on the Plantar and Dorsal Aspect of the Foot Increases the FMA of the Lower Limb for Poststroke Patients in Brunnstrom Stage III: A Preliminary Study

The withdrawal reflex is a defensive reaction to nociceptive stimuli and can be used to regulate locomotor gait during rehabilitation. We investigated the effect of successive needle-pricking of the plantar and dorsal foot surfaces on poststroke lower limb function. Thirty-five hemiplegic patients, within one month after primary stroke, with an affected lower limb (Brunnstrom stage III) were randomly divided into intervention and control groups. Both groups received routine drug treatment, rehabilitation training, and upper limb acupuncture treatment on the hemiplegic side. The control group also received routine acupuncture on the hemiplegic side of the lower limb, while the intervention group received successive needle-pricking on the sole and instep of both the unaffected and affected side feet. Outcomes were assessed before inception (D0) and after three (D3) and six (D6) treatment days, using Brunnstrom stage (Ueda assessment), total Fugl–Meyer lower extremity assessment (FMA-LE) and its subscores (FMA-LE-ss), active lower limb range of motion (AROM-LL), Modified Ashworth Scale Score (MAS-LL), and manual muscle testing (MMT-LL). The Brunnstrom stage was better in the intervention group than in the control group at both D3 and D6 P<0.01. The total FMA-LE score and sections B, C, D, and G FMA-LE-ss were significantly better in the intervention group than in the control group at D3 and D6 P<0.05. The AROM-LL hip and knee flexion and hip extension improved more in the intervention group than in the control group P<0.05. In the intervention group, MAS-LL hip flexion significantly improved at D6 P<0.01. Improvement in lower limb joints on the MMT-LL in the intervention group exceeded that in the control group at D6 P<0.01. Successive needle-pricking on the plantar and dorsal foot aspects of Brunnstrom stage III in poststroke patients contributed to rapid lower limb motor function improvement via the withdrawal reflex. This trial is registered with ChiCTR1900020633.