Abstract |
In vitro twitch characteristics of the semimembranosus muscle were evaluated in 9 clinically normal horses, in 15 horses with chronic intermittent rhabdomyolysis (CIR) and in 2 horses with myotonia. Effects of phenytoin on in vitro muscle twitch and clinical signs of CIR and myotonia were evaluated in these same horses. Times to 90% relaxation were prolonged in the horses with CIR (mean +/- SEM, 186 +/- 5.9 ms) and in 2 horses with myotonia (197 and 177 ms) compared with those in clinically normal horses (mean +/- SEM, 146 +/- 2.1 ms). Horses with CIR also had significantly (P less than 0.05) longer times to 50% relaxation, compared with clinically normal horses. In the group of horses with CIR, Standardbreds had significantly (P less than 0.05) longer times to 90% and 50% relaxation, compared with Thoroughbreds. Times to 100% peak tension did not differ among the groups. Administration of phenytoin directly into a muscle preparation bath solution had no effect on muscle twitch properties. After the initial muscle biopsy, phenytoin was administered orally for 7 to 10 days to 4 horses with CIR, 2 myotonic horses, and 2 clinically normal horses before repeat biopsy from the same site in the contralateral semimembranosus muscle. Times to 90% relaxation decreased from 197 and 177 ms to 144 and 126 ms, respectively, in the 2 myotonic horses, from a mean of 192 (+/- 9) ms to 170 (+/- 9) ms in the 4 horses with CIR and remained unchanged (154 and 140 ms before vs 155 and 139 ms after treatment) in the 2 clinically normal horses.(ABSTRACT TRUNCATED AT 250 WORDS)
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Authors | J Beech, J E Fletcher, F Lizzo, J Johnston |
Journal | American journal of veterinary research
(Am J Vet Res)
Vol. 49
Issue 12
Pg. 2130-3
(Dec 1988)
ISSN: 0002-9645 [Print] United States |
PMID | 3239850
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
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Chemical References |
- Phenytoin
- Creatine Kinase
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Topics |
- Administration, Oral
- Animals
- Chronic Disease
- Creatine Kinase
(analysis)
- Female
- Gait
- Horse Diseases
(drug therapy)
- Horses
(blood, physiology)
- In Vitro Techniques
- Male
- Muscle Contraction
(drug effects)
- Myotonia
(drug therapy, physiopathology, veterinary)
- Phenytoin
(administration & dosage, therapeutic use)
- Rhabdomyolysis
(drug therapy, physiopathology, veterinary)
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