Abstract
The use of fish models in biomedical research is increasing. Since behavioural and physiological consequences of surgical procedures may affect experimental results, these effects should be defined and, if possible, ameliorated. Thus, the use of post-surgical analgesia should be considered after invasive procedures also in fish, but presently, little information exists on the effects of analgesics in fish. This study assessed the effects of an opioid drug, buprenorphine (0.05 mg/kg IM), on resting ventilation and heart rates during 7 days of postsurgical recovery in rainbow trout (Oncorhynchus mykiss) at 10°C by non-invasively recording bioelectric potentials from the fish via electrodes in the water. Baseline ventilation and heart rates were considerably lower compared to previously reported values for rainbow trout at 10°C, possibly due to the non-invasive recording technique. Buprenorphine significantly decreased both ventilation and heart rates further, and the effects were most pronounced at 4–7 days after anaesthesia, surgical procedures and administration of the drug. Somewhat surprisingly, the same effects of buprenorphine were seen in the two control groups that had not been subject to surgery. These results indicate that the reductions in ventilation and heart rates are not caused by an analgesic effect of the drug, but may instead reflect a general sedative effect acting on both behaviour as well as e.g. central control of ventilation in fishes. This resembles what has previously been demonstrated in mammals, although the duration of the drug effect is considerably longer in this ectothermic animal. Thus, before using buprenorphine for postoperative analgesic treatment in fish, these potentially adverse effects need further characterisation.
Highlights
The use of fish as models in bio-clinical research is increasing [1,2]
The overall temporal heart rate pattern was mirrored in the heart rate variability (HRV) response, which gradually increased during the first 3-5 days
Buprenorphine significantly decreased both ventilation and heart rates and the effects were most pronounced at 4–5 days after the anaesthesia, surgical procedures and administration of the drug
Summary
The use of fish as models in bio-clinical research is increasing [1,2]. Normally when animals are used in veterinary practice or experimental research, different forms of postsurgical analgesics are administered to alleviate postsurgical pain and speed up recovery from the surgical intervention. Fish that undergo invasive procedures have not been given any form of post-surgical analgesia [1]. This is likely due to the fact that we today still know little about how fish perceive and react to pain. If fish do perceive pain, an attempt to minimize this is important from a welfare perspective, and desired from the researcher’s point of view as it will likely increase the quality and reliability of the experimental data. It has been suggested that much historical physiological data for fish may be biased due to poor post-surgical recovery of the animals [5,6,7]
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