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- Author or Editor: Sheldon A. Steinberg x
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Abstract
Objective—To determine whether intrathecal (IT) or IV administration of oxytocin will diminish amplitude of the reflex-evoked muscle action potential (REMP) in the digastricus muscle during electrical stimulation of the tooth pulp in anesthetized dogs, thus suggesting an analgesic effect for oxytocin.
Animals—6 male Beagles that were 2 to 6 years old.
Procedure—Dogs were used in a crossover design with at least a 5-day washout period between treatments. Each dog received morphine, saline (0.9% NaCl) solution, and oxytocin by both the IT and IV routes of administration. Noninvasive dental dolorimetry was used to assess changes in pain threshold following administration of treatments. Effectiveness of analgesia was determined on the basis of change in REMP amplitude in the digastricus muscle.
Results—Morphine administered IV significantly inhibited REMP amplitude, compared with IV administration of saline solution or oxytocin. There was not a significant change in REMP amplitude between saline solution and oxytocin administered IV. Intrathecal administration of morphine significantly inhibited REMP amplitude, compared with IT administration of saline solution or oxytocin. Intrathecal administration of oxytocin significantly increased REMP amplitude, compared with IT administration of saline solution or morphine.
Conclusions and Clinical Relevance—Although IV administration of oxytocin did not have an effect on REMP amplitude, compared with IV administration of saline solution, IT administration of oxytocin had the opposite effect of morphine and increased REMP amplitude of the digastricus muscle. These data do not support the use of oxytocin as an analgesic agent in dogs. (Am J Vet Res 2002;63:1354–1358)
Summary
Cytosolic assay was used to detect gonadal steroid receptors in brain tumor tissue from 6 dogs and 2 cats. For 4 samples, the maximal number of binding sites and the equilibrium dissociation constant were calculated, using Scatchard analysis. The concentration of receptor protein that was discovered was similar to that detected in hormone-sensitive tumors.
Abstract
Objective—To determine whether changes in amplitude of the reflex-evoked muscle action potential (REMP) elicited by noninvasive dental dolorimetry (electrical stimulation of the tooth pulp) in anesthetized dogs may be used to objectively evaluate the effectiveness of IV and intrathecal (IT) administration of morphine.
Animals—6 male Beagles that were 2 to 6 years old.
Procedure—Dogs were used in a crossover design with at least a 5-day washout period between treatments. Each dog received morphine, saline (0.9% NaCl) solution, and oxytocin via the IV and IT routes of administration; however, only results for morphine and saline treatments were reported here. Dogs were anesthetized and prepared for noninvasive dental dolorimetry. After IV or IT administration, electrical stimulation was applied to a tooth, and REMPs of the digastricus muscle were recorded at 5-minute intervals for 60 minutes. To determine differences in REMP amplitude between treatments, a linear regression line was fitted for each dog-treatment combination.
Results—The IV administration of morphine significantly inhibited REMP amplitude, compared with IV administration of saline solution. Intrathecal administration of morphine significantly inhibited REMP amplitude, compared with IT administration of saline solution.
Conclusions and Clinical Relevance—Noninvasive dental dolorimetry in anesthetized dogs has promise as a technique for use in evaluating the analgesic potential of drugs administered IV and IT through evaluation of their effect on REMP amplitude recorded for the digastricus muscle. (Am J Vet Res 2002;63: 1349–1353)
Summary
Gamma-vinyl-γ-aminobutyric acid is a novel antiepileptic drug that exerts its effects by increasing the concentration of γ-aminobutyric acid in the brain. The mechanism of action involves irreversible inhibition of the metabolic pathway of γ-aminobutyric acid. The drug was administered to 14 dogs in conjunction with other anticonvulsants, in an attempt to control refractory epilepsy. Four of these dogs had clinically relevant evidence of decreased seizure frequency. In 4 dogs, response to the drug was no better than response to phenobarbital alone. In 2 dogs, seizure control improved, but γ-vinyl-γ-aminobutyric acid was withdrawn because of development of hemolytic anemia. For various reasons, the therapeutic effect in the remaining 4 dogs could not be evaluated.
This study of only 14 dogs illustrates some of the problems that confound our ability to judge the efficacy of anticonvulsant treatment.
Summary
The medical records of 18 dogs that had hepatic disease and received phenobarbital as an anticonvulsant for 5 to 82 months were reviewed. Clinical signs included sedation and ataxia in all dogs, 5 dogs were also anorectic, 2 had coagulopathy, 3 were icteric, and 5 had ascites. Serum biochemical analysis revealed serum albumin concentration ≤ 2.2 g/dl in 12 dogs, serum alkaline phosphatase activity ≥ 169 U/L in 18 dogs, serum alanine transaminase activity ≥ 57 U/L in 15 dogs, and total bilirubin concentration ≥ 1 mg/dl (in the absence of lipemia) in 7 dogs.
Serum phenobarbital concentration was ≥ 40 μg/ml in 12 of 17 dogs. Sulfobromophthalein excretion was prolonged in 8 of 10 dogs. Preprandial serum bile acid concentrations were high in 8 of 10 dogs, and 2-hour postprandial serum bile acid concentrations were high in 9 of 10 dogs. Two of 4 dogs tested had resting plasma ammonia concentrations > 200 mg/dl. An ammonia tolerance test was performed on 2 other dogs; both had ammonia concentration ≥ 200 mg/dl in the plasma 30 minutes after receiving 100 mg of ammonium chloride/kg of body weight, po.
Nine dogs died, 1 was euthanatized, and necropsies were performed on these 10 dogs. Biopsies and necropsies of 6 dogs revealed chronic hepatic fibrosis with nodular regeneration (cirrhosis). One dog had hepatocellular carcinoma and mild cirrhosis. In 1 dog, after phenobarbital had been withheld, necropsy revealed complete recovery of the previously observed lesions.
Abstract
Objective—To determine whether neurologic examination findings, results of CSF analysis, or age at the onset of seizures could be used to predict whether results of magnetic resonance imaging (MRI) would be normal or abnormal in dogs with seizures.
Design—Retrospective study.
Animals—115 dogs.
Procedure—Information on results of neurologic examination, results of CSF analysis, age at the onset of seizures, and results of MRI was obtained from the medical records.
Results—Results of MRI were abnormal in 61 dogs and normal in 54. Sensitivity and specificity of neurologic examination alone were 77 (47/61) and 91% (49/54), respectively. Sensitivity and specificity of CSF analysis alone were 79 (48/61) and 69% (37/54), respectively. Results of MRI were abnormal for 12 of 28 (43%) dogs with abnormal CSF analysis results and normal neurologic examination results but for only 2 of 35 (6%) dogs with normal CSF analysis and normal neurologic examination results. Similarly, results of MRI were abnormal for 36 of 37 (97%) dogs with abnormal CSF analysis and abnormal neurologic examination results but for only 11 of 15 (73%) dogs with normal CSF analysis results and abnormal neurologic examination results. Age at the onset of seizures (< 6 vs ≥ 6 years old) was not significantly associated with results of MRI.
Conclusions and Clinical Relevance—Results suggest that neurologic examination findings and results of CSF analysis are useful in predicting whether results of MRI will be abnormal in dogs examined because of seizures, but age at the onset of seizures is not. (J Am Vet Med Assoc 2002;220:781–784)
Abstract
Objective—To determine prevalence of seizures after use of iohexol for myelography and identify associated risk factors in dogs.
Design—Retrospective study.
Animals—182 dogs that received iohexol for myelography in 1998.
Procedure—Medical records were reviewed for age, breed, sex, weight, dose and total volume of iohexol, injection site, number of injections, lesion type and location, total duration of anesthesia, duration from time of iohexol injection to recovery, presence and number of seizures, and whether surgery followed the myelogram.
Results—39 (21.4%) dogs had at least 1 generalized seizure during or after myelography. Injection site was strongly associated with prevalence of seizures, and risk of seizure was significantly higher after cerebellomedullary injections, compared with lumbar injections. Mean total volume of iohexol administered to dogs that had seizures was significantly higher, compared with that administered to dogs that did not have seizures, although dosage did not differ between groups. Weight was significantly correlated with risk of seizure, and dogs that weighed > 20 kg (44 lb) had higher prevalence of seizures than dogs that weighed < 20 kg.
Conclusions and Clinical Relevance—It is preferential to administer iohexol via the L5-6 intervertebral space to minimize the risk of seizures. Higher prevalence of seizures in large dogs, compared with smaller dogs, may be caused by administration of larger total volumes of contrast agent per volume of CSF. (J Am Vet Med Assoc 2002;220:1499–1502)