EFFECT OF XYLAZINE, CISAPRIDE, AND NALOXONE ON MYOELECTRIC ACTIVITY OF THE ILEOCECOCOLIC AREA IN COWS

The effect of xylazine, cisapride, and naloxone on myoelectric activit y of the ileum, cecum, and proximal loop of the ascending colon (PLAC) was determined in 4 healthy Jersey cows implanted with 8 pairs of bip olar 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 mi). All treatments were administered IV during early phase I of the migrating myoelectric complex in the ileum. Myoelectric activity was recorded f or 4 hours after treatment, and data were analyzed for each hour separ ately. Xylazine significantly (P < 0.05) increased the duration of pha se I of the first migrating myoelectric complex in the ileum to 220.72 +/- 26.89 minutes, compared with 30.91 +/- 10.11 minutes after admini stration of 0.9% sodium chloride solution. The number of cecocolic spi kes per minute per electrode and the duration of cecocolic spike activ ity (percentage of recording time) were significantly (P < 0.05) decre ased for the first 3 hours, and the number of propagated spike sequenc es in the cecum and PLAC was significantly (P < 0.05) decreased for th e first 2 hours after administration of xylazine. Significant differen ce was not found between control and either cisapride or naloxone trea tment of healthy cows. However, during hour 1 after treatment with cis apride, number of spikes per minute, duration of spike activity, and n umber of propagated spike sequences were highest, compared with the ot her treatments. It was concluded that naloxone at the dosage used in t his study was not suitable for medical treatment of cecal dilatation i n cattle, when hypomotility of the cecum and PLAC must be reversed. Xy lazine should not be used for relief of signs of pain in cases of ceca l 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 me dical treatment of cecal dilatation in cattle needs further evaluation .