NALOXONE AFFECTS GASTROINTESTINAL FUNCTIONS AND BEHAVIOR IN HORSES

Clinical effects of the opioid antagonist naloxone were investigated i n healthy horses. Naloxone caused a transient increase in the frequenc y of defaecations, a softening of the faeces and alterations in the in tensity of abdominal borborygmi. Total serum protein concentrations de creased. Behavioural changes like frequent yawning and flehmen occurre d, heart rate decreased and respiratory rate tended to increase but no clinical signs of distress or pain were observed. It can be concluded that in healthy animals naloxone had only minor side-effects and coul d be used to investigate the physiological functions of endogenous opi oids in horses