Electromyographic (EMG) evaluation of the external urethral sphincter (EUS) was conducted during cystometry in 11 adult male cats sedated with xylazine and ketamine. A percutaneously placed antepubic catheter was used for bladder infusion and recording intravesicular pressures during cystometrography (CMG). A fine-wire electrode was placed percutaneously into or near the EUS for recording EMG during CMG. The bladder was infused with sterile 0.9% NaCl solution at a rate of 2 to 3 ml/min until a detrusor reflex was initiated. Intravesicular pressures at the onset of infusion, immediately prior to micturition, at the onset of urine flow, and at the maximal voiding pressure were recorded. The time from infusion to micturition, from opening pressure to return to baseline, and from the beginning to the end of the CMG were also recorded. The total volume of 0.9% NaCl solution infused and the residual bladder volume after micturition were also measured. Recordings were replicated once during each trial in all cats, and trials were replicated once approximately 1 week later in 4 cats. Micturition patterns were characterized by slight to moderate EUS EMG activity during vesicular filling, with reduction in activity during emptying. Maximal EMG activity was recorded at the completion of the reflex and was associated with pulsatile expulsion of small amounts of urine. The simultaneous recording of CMG and EUS EMG with fine-wire electrodes was simple and reliable for assessing the neuromuscular integrity and synchrony of detrusor and EUS muscles. There were no significant differences in variables between recordings within trial 1, but there were differences (P less than or equal to 0.05) between trials for pressure at the onset of urine flow and maximal voiding pressure.

The innervation of the levator ani and coccygeal muscles and the external anal sphincter was studied by anatomic dissection in 6 clinically normal male dogs and by electrical stimulation in 5 clinically normal male dogs. Variations in innervation occasionally were found that were comparable to those reported in previous studies. Electromyographic recordings were made from the levator ani and coccygeal muscles and from the anal sphincter in 40 dogs during perineal hernia repair. Spontaneous potentials of 4 types were found in 35 dogs: fibrilation potentials, positive sharp waves, complex repetitive discharges, and fasciculations. Biopsy specimens of the cranial part of the levator ani muscle were taken in 12 dogs during perineal hernia repair. Histologic examination revealed atrophy in 7 specimens. Spontaneous potentials were recorded from all muscles with histologic evidence of atrophy. All examinations of the levator ani muscle concerned the cranial, part of this muscle, because the caudal part was absent in all 40 dogs. From combined results of electromyography and histologic examination, it was concluded that atrophy of the muscles of the pelvic diaphragm, which develops in some dogs with perineal hernia, is likely to be of neurogenic origin. Nerve damage is localized in the sacral plexus proximal to the muscular branches of the pudendal nerve or in the muscular branches separately.

OBJECTIVE To quantify fatigue-induced electromyographic changes in hind limb muscles in horses. ANIMALS 8 Thoroughbreds. PROCEDURES The left and right hind limb longissimus dorsi, tensor fasciae latae, gluteus medius, and biceps femoris muscles were instrumented for surface electromyography. Hoof strain gauges were attached to confirm stride cycle. Each horse was galloped on a treadmill (grade, 3%) at a constant speed (12.6 to 14.7 m/s) to achieve fatigue after approximately 360 seconds. Before and after this exercise, the horses were trotted at 3.5 m/s. At 30-second intervals during galloping an integrated electromyography (iEMG) value for a stride and the median frequency of muscle discharge (MF) in each limb were measured. The mean of stride frequency (SF), iEMG value, and MF of 5 consecutive strides at the start and end of galloping for the lead and trailing limbs were compared. For trotting, these variables were compared at 60 seconds before and after galloping. RESULTS The mean ± SD value for SF decreased over time (2.14 ± 0.06 to 2.05 ± 0.07 stride/s). In both the lead and trailing limbs, fatigue decreased the iEMG values of the gluteus medius and biceps femoris muscles but not those of the longissimus dorsi and tensor fasciae latae muscles. The MF did not change for any muscle during galloping with fatigue. The SF, iEMG value, and MF did not change during trotting with fatigue. CONCLUSIONS AND CLINICAL RELEVANCE Fatigue induced by high-speed galloping decreased the gluteus medius and biceps femoris muscles' iEMG values in Thoroughbreds. Fatigue of these less fatigue-resistant hind limb muscles would affect a horse's speed.

OBJECTIVE To evaluate the effects of exercise in an underwater treadmill (UWT) on forelimb biomechanics and articular histologic outcomes in horses with experimentally induced osteoarthritis of the middle carpal joint. ANIMALS 16 horses. PROCEDURES An osteochondral fragment was induced arthroscopically (day 0) in 1 middle carpal joint of each horse. Beginning on day 15, horses were assigned to exercise in a UWT or in the UWT without water (simulating controlled hand walking) at the same speed, frequency, and duration. Thoracic and pelvic limb ground reaction forces, thoracic limb kinematics, and electromyographic results for select thoracic limb muscles acting on the carpi were collected on days -7 (baseline), 14, 42, and 70. Weekly evaluations included clinical assessments of lameness, response to carpal joint flexion, and goniometric measurements of thoracic limb articulations. At study conclusion, articular cartilage and synovial membrane from the middle carpal joints was histologically examined. RESULTS Exercise in a UWT significantly reduced synovial membrane inflammation and resulted in significant clinical improvements with regard to symmetric thoracic limb loading, uniform activation patterns of select thoracic limb muscles, and return to baseline values for carpal joint flexion, compared with results for horses with simulated hand walking. CONCLUSIONS AND CLINICAL RELEVANCE Overall improvements in thoracic limb function, joint range of motion, and synovial membrane integrity indicated that exercise in a UWT was a potentially viable therapeutic option for the management of carpal joint osteoarthritis in horses.

Objective--To determine whether larkspur-derived N-(methylsuccinimido) anthranoyllycoctonine (MSAL)-type alkaloids alter heart rate and electrically evoked electromyographic (eEMG) response of the external anal sphincter (EAS) in cattle and whether these effects can be reversed by acetylcholinesterase inhibitors. Animals--12 beef heifers and 4 cows. Procedures--3 or 4 heifers were used in 1 or 2 of 7 dose-response experiments; heart rate and EAS eEMG response were assessed before and 24 hours after oral treatment with larkspur (doses equivalent to 0.5 to 15 mg of MSAL-type alkaloids/kg). In 3 subsequent experiments, 3 heifers (1 of which was replaced with another heifer in the control experiment) each received 10 mg of MSAL-type alkaloids/kg and were injected IV with physostigmine (0.04 mg/kg), neostigmine (0.04 mg/kg), or saline (0.9% NaCl) solution 24 hours later, prior to assessment. Additionally, EAS eEMG response was measured in 4 cows before and after epidural administration of 2% lidocaine hydrochloride. Results--Larkspur-treated heifers developed dose-related increases in heart rate and decreases in EAS eEMG response. Twenty-four hours after administration of MSAL-type alkaloids, neostigmine decreased heart rate but did not affect eEMG response, whereas physostigmine did not affect heart rate but caused a 2-fold increase in eEMG response. In cows, epidural anesthesia did not alter eEMG response, suggesting that transdermal stimulation of the EAS pudendal innervation did not occur. Conclusions and Clinical Relevance--In cattle, cardiac effects and muscle weakness or loss of EAS eEMG response induced by larkspur-derived MSAL-type alkaloids were reversed by neostigmine or physostigmine, respectively. Treatment with anticholinesterase inhibitors may alter the clinical effects of larkspur poisoning in cattle.

Objective-To investigate the effects of IV administration of ergotamine and ergovaline and intraruminal administration of ergotamine on electromyographic (EMG) activity of reticuloruminal smooth muscle in conscious sheep. Animals-3 sheep with indwelling electrodes in the musculature of the reticulum and rumen. Procedure-In a crossover design study, reticuloruminal motility before and after IV administration of ergotamine (5, 10, 20, and 40 nmol/kg) or ergovaline (2.5, 5, and 10 nmol/kg) was evaluated; EMG effects were compared with those of corresponding control treatments (IV administration of saline 0.9% NaCl solution or acetone, respectively) in sheep. Ergotamine (800 nmol/kg) or water was also administered intraruminally and their effects compared. Results-After IV administration of ergopeptides, vagally dependent cyclical A and B sequences of contraction of the reticulorumen were immediately inhibited, preceding increases in baseline EMG activity (tonus). The return of cyclical contractions was associated with an increase in contraction amplitude. The effects were dose dependent; administration of 40 nmol of ergotamine/kg resulted in responses that continued for 3 to 4 hours. The effects of intraruminal administration of ergotamine were variable; after 8 hours, EMG activity was increased from baseline for < 2 hours in 1 sheep, 10 hours in another, and > 15 hours in the third. Conclusions and Clinical Relevance-In sheep, the effects of ergotamine and ergovaline on reticuloruminal motility after IV administration and the duration of responses following intraruminal administration suggest that disruption of digestion may occur in animals grazing endophyte-infected pasture that has a high ergopeptide content.

Objective-To determine the influence of age on results of quantitative analysis of electromyographic (EMG) needle examination in the subclavian, triceps, and lateral vastus muscles of Dutch Warmblood horses. Animals-7 healthy young Dutch Warmblood horses (range, 13 to 18 months old), 7 healthy adult Dutch Warmblood horses (range, 4 to 10 years old), and 7 healthy elderly Dutch Warmblood horses (range, 18 to 21 years old). Procedure-An EMG needle examination was performed to evaluate insertional activity, spontaneous activity, and motor unit action potential (MUAP) variables. Although all horses were conscious, young horses were sedated prior to examination. Results-Mean insertional activity in young horses was significantly lower than in elderly horses. Pathologic spontaneous activity was rarely found in young and adult horses but was frequently evident in all muscles in all elderly horses. The MUAP duration and amplitude were significantly lower in all muscles of young horses, compared with values for adult and elderly horses. The MUAP duration and number of phases and turns were significantly lower in adult horses than in elderly horses. Group differences for percentages of polyphasic and complex MUAPs were also found. The 95% confidence intervals for MUAP duration, MUAP amplitude, and number of phases and turns for the subclavian, triceps, and lateral vastus muscles were significantly lower in young horses than in adult or elderly horses. Conclusion and Clinical Relevance-Age of the horse being examined should be considered when EMG examination is performed.

The effect of xylazine, cisapride, and naloxone on myoelectric activity of the ileum, cecum, and proximal loop of the ascending colon (PLAC) was determined in 4 healthy Jersey cows implanted with 8 pairs of bipolar electrodes. A 4 X 4 Latin square design was used. The treatments included xylazine (0.04 mg/kg of body weight), cisapride (0.08 mg/kg), naloxone (0.05 mg/kg), and 0.9% sodium chloride solution (20 ml). All treatments were administered IV during early phase I of the migrating myoelectric complex in the ileum. Myoelectric activity was recorded for 4 hours after treatment, and data were analyzed for each hour separately. Xylazine significantly (P < 0.05) increased the duration of phase I of the first migrating myoelectric complex in the ileum to 220.72 +/- 26.89 minutes, compared with 30.91 +/- 10.11 minutes after administration of 0.9% sodium chloride solution. The number of cecocolic spikes per minute per electrode and the duration of cecocolic spike activity (percentage of recording time) were significantly (P < 0.05) decreased for the first 3 hours, and the number of propagated spike sequences in the cecum and PLAC was significantly (P < 0.05) decreased for the first 2 hours after administration of xylazine. Significant difference was not found between control and either,cisapride or naloxone treatment of healthy cows. However, during hour 1 after treatment with cisapride, number of spikes per minute, duration of spike activity, and number of propagated spike sequences were highest, compared with the other treatments. It was concluded that naloxone at the dosage used in this study was not suitable for medical treatment of cecal dilatation in cattle, when hypomotility of the cecum and PLAC must be reversed. Xylazine should not be used for relief of signs of pain in cases of cecal dilatation, because it significantly reduced myoelectric activity of the cecum and PLAC for at least 2 hours after treatment. Furthermore, results of this study indicated a trend (P > 0.05) toward increase of cecocolic myoelectric activity after administration of cisapride. It is the authors' opinion that the potential benefit of cisapride for medical treatment of cecal dilatation in cattle needs further evaluation.

The innervation of the levator ani and coccygeal muscles and the external anal sphincter was studied by anatomic dissection in 6 clinically normal male dogs and by electrical stimulation in 5 clinically normal male dogs. Variations in innervation occasionally were found that were comparable to those reported in previous studies. Electromyographic recordings were made from the levator ani and coccygeal muscles and from the anal sphincter in 40 dogs during perineal hernia repair. Spontaneous potentials of 4 types were found in 35 dogs: fibrilation potentials, positive sharp waves, complex repetitive discharges, and fasciculations. Biopsy specimens of the cranial part of the levator ani muscle were taken in 12 dogs during perineal hernia repair. Histologic examination revealed atrophy in 7 specimens. Spontaneous potentials were recorded from all muscles with histologic evidence of atrophy. All examinations of the levator ani muscle concerned the cranial, part of this muscle, because the caudal part was absent in all 40 dogs. From combined results of electromyography and histologic examination, it was concluded that atrophy of the muscles of the pelvic diaphragm, which develops in some dogs with perineal hernia, is likely to be of neurogenic origin. Nerve damage is localized in the sacral plexus proximal to the muscular branches of the pudendal nerve or in the muscular branches separately.

Evaluation of urethral pressure profilometry (UPP) with simultaneous fine-wire electromyography of the external urethral sphincter (EUS) was conducted in 11 healthy adult male cats sedated with xylazine and ketamine. A 3.5-F urethral catheter with a closed end and two 1-mm sideports was infused with sterile 0.9% NaCl solution at a rate of 2 to 3 ml/min. A fine-wire electromyographic (EMG) electrode was placed percutaneously into or near the external urethral sphincter prior to the onset of the UPP. The maximal urethral pressure achieved and functional profile length were recorded from UPP. Setting both catheter withdrawal rate and paper speed at 5 mm/s enabled the measurement of actual urethral length directly from UPP. Sphincter EMG activity was rated as slight (+), moderate (+ +), or intense (+ + +). All recordings were replicated once during each trial for 8 cats and trials were replicated 5 to 7 days later in 4 cats. Before catheterization, EMG activity of the external urethral sphincter was rated slight (+), whereas intense (+ + +) activity accompanied insertion. The activity evoked by movement of the catheter subsided, but intense EMG activity of the external urethral sphincter was recorded from onset to completion of catheter withdrawal in all cats in both trials. The mean maximal urethral pressure was 93.1 +/- 13.29 cm H2O. The mean function urethral length was 8.1 +/- 0.93 cm. Maximal urethral pressure or function profile length did not differ significantly between recordings within trials or between trials. Simultaneous recording of EMG activity and UPP of the external urethral sphincter was shown to be a simple, noninvasive technique for assessing neuromuscular and anatomic urethral function.