Evaluation of the anesthetic effects of MS222 in the adult Mexican axolotl (Ambystoma mexicanum)

Chiara Zullian,1 Aurore Dodelet-Devillers,1 Stéphane Roy,2 Pascal Vachon1 1Département de Biomédecine Vétérinaire, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, 2Département de Stomatologie, Faculté de Médecine Dentaire, Montréal, Québec, Canada Abstract: The Mexican axolotl (Ambystoma mexicanum) is a unique research model in several fields of medicine, where surgical and invasive procedures may be required. As yet, little is known about the efficacy of MS222 (tricaine methanesulfonate), which is the most commonly used anesthetic agent in amphibians. The main objectives of this study were to evaluate the anesthetic effects and physiological changes in adult axolotls following a 20-minute immersion bath, containing progressive MS222 concentrations starting at 0.1%. Depth of anesthesia and physiological changes were evaluated every 15 minutes post-MS222 exposure with the following parameters: righting behavior, withdrawal reflex, acetic acid test response, heart rate, and blood oxygen saturation, as well as cloacal and body surface temperatures. A 20-minute exposure in a 0.1% MS222 immersion bath (n=6 animals) had no anesthetic effects on adult axolotls after 20 minutes of exposure. With a 0.2% MS222 solution, all axolotls (n=9) were deeply anesthetized at 15 minutes, and 80% were still unresponsive at 30 minutes postexposure. Blood oxygen saturation and heart rate were slightly, but significantly, increased when compared with the baseline value and remained stable up to recovery. There was no significant increase in surface and cloaca temperatures, compared with baseline. With the 0.4% MS222 solution, the duration of anesthesia lasted for 90 minutes to at least 120 minutes (n=3 animals) and this concentration was deemed too high. In conclusion, a 20-minute immersion bath with 0.2% MS222 may be used for short procedures (15–30 minutes) requiring anesthesia of adult axolotls. Keywords: Ambystoma mexicanum, axolotl, amphibians, anesthesia, pai

Effects of alpha(2)-adrenergic drugs on small intestinal motility in the horse: An in vitro study

The effects of selective a2-agonists (xylazine, detomidine and medetomidine) and antagonists (yohim- bine and atipamezole) on in vitro small intestine motility in the horse were evaluated. Samples of equine jejunum were placed in isolated organ baths and drug-induced modifications of motility were measured by means of an isotonic transducer. All tested a2-agonists dose-dependently reduced both spontaneous and electrically-evoked phasic contractions. Conversely, a2-antagonists were ineffective when tested alone, and showed a heterogeneous and dose-independent ability to inhibit agonist activity. In particular, the antagonism exerted by higher concentrations of both yohimbine and atipamezole against a2-agonists was weaker than when lower concentrations were used. The data are indicative of the presence of both pre- and post-synaptic a2-adrenoceptors with inhibitory activity on equine jejunum motility, and sup- port a possible therapeutic utility of these drugs in horse intestinal disorders associated with hypermotility

Inhibition of motility in isolated horse small intestine mediated by κ- but not μ-opioid receptors

The effects of preferential m (morphine), selective m (fentanyl), selective k (compound U69593) opioid receptor agonists, and nonselective (naloxone) and selectivem(naloxonazine) antagonists on equine small intestinal motilitywere evaluated in vitro. Samples of circular muscle fromequine jejunumwere placed in isolated organ baths and drug-induced modifications of both spontaneous and electrically evoked contractile activity were measured. None of the opioid agonists induced a significant change in spontaneous contractions. Fentanyl and U69593 reduced electrically induced contractions, whereas morphine reduced them only slightly. Naloxone competitively antagonised U69593, but both naloxone and naloxonazine were unable to counteract the inhibition of contractions induced by fentanyl. The inhibition of contractions shown by fentanyl is therefore probably not mediated by opioid receptors, but due to an anticholinergic activity of this drug. In summary, these data showed an inhibitory effect exerted by k receptors on equine small intestinal motility, whereas the role of m receptors seemed marginal and would need further characterisation

Effect of oral curcumin on indomethacin-induced small intestinal damage in the rat.

Nonsteroidal anti-inflammatory drug (NSAID)-induced injury on gastrointestinal tract is well documented, and jejunal inflammation caused by indomethacin in rats is a broadly used experimental model of enteritis. We evaluated the effect of oral curcumin, a compound known to possess anti-inflammatory and anti-oxidant properties, on indomethacin-induced enteritis in the rat. Curcumin (50, 100, and 300 mg/kg) was given to rats by oral gavage 48, 24, and 1 h before enteritis was induced by intragastric administration of 20 mg/kg indomethacin. After 24 h, intestinal macroscopic lesions, myeloperoxidase activity and lipid peroxidation levels were assessed. Curcumin at the dose of 50 mg/kg was uneffective, while at the dose of 100 and 300 mg/kg significantly reduced macroscopic damage caused by indomethacin. By contrast, curcumin at all tested doses was unable to modify indomethacin-induced increases of myeloperoxidase and lipid peroxidation. Curcumin (100 and 300 mg/kg) significantly increased lipid peroxidation level in normal intestinal tissues of rats. Present data show that oral curcumin protects against macroscopic injury induced by indomethacin, leaving unaffected neutrophil infiltration and oxidative cell damage, thus suggesting that this beneficial effect is due to mechanisms not involving anti-inflammatory or anti-oxidant activities

Effects of nonselective and selective cyclooxygenase inhibitors on small intestinal motility in the horse

We investigated the effects of nonselective cyclooxygenase (COX) inhibitors (indomethacin and flunixin meglumine) and selective COX-1 (SC-560) or COX-2 (celecoxib, DUP-398 and NS-697) inhibitors on horse small bowel motility in vitro. At this purpose, samples of equine ileum were put in isolated organ baths for the motility experiments. Nonselective COX inhibitors were devoid of major effects on motility, except for an inhibition of tonic contraction shown by flunixin meglumine. SC-560, selective COX-1 inhibitor, was devoid of significant effects on ileal motility. Selective COX-2 inhibitors reduced both tonic contraction and spontaneous phasic contractions, while prostaglandin (PG) receptor antagonists were uneffective. Some of the intestinal samples were submitted to histological investigation or reverse transcription-polymerase chain reaction (RT-PCR), which revealed the presence of an inflammation reaction and the presence of both COX isoforms mRNAs. Present data support the hypothesis that the effects of COX inhibitors on horse small intestinal motility are not linked to PG depletion

Effects of nonselective and selective cyclooxygenase inhibitors on small intestine motility in the horse

We investigated the effects of nonselective cyclooxygenase (COX) inhibitors (indomethacin and flunixin meglumine) and selective COX-1 (SC-560) or COX-2 (celecoxib, DUP-398 and NS-697) inhibitors on horse small bowel motility in vitro. At this purpose, samples of equine ileum were put in isolated organ baths for the motility experiments. Nonselective COX inhibitors were devoid of major effects on motility, except for an inhibition of tonic contraction shown by flunixin meglumine. SC-560, selective COX-1 inhibitor, was devoid of significant effects on ileal motility. Selective COX-2 inhibitors reduced both tonic contraction and spontaneous phasic contractions, while prostaglandin (PG) receptor antagonists were uneffective. Some of the intestinal samples were submitted to histological investigation or reverse transcription-polymerase chain reaction (RT-PCR), which revealed the presence of an inflammation reaction and the presence of both COX isoforms mRNAs. Present data support the hypothesis that the effects of COX inhibitors on horse small intestinal motility are not linked to PG depletion