The effects of tricaine methanesulfonate (MS-222) on plasma nonesterified fatty acids in rainbow trout, Oncorhynchus mykiss.

The effects of tricaine methanesulfonate (MS-222), a commonly used fish anesthetic, on plasma nonesterified fatty acid levels (NEFA) were examined in rainbow trout, Oncorhynchus mykiss. Total NEFA levels declined with increasing duration of exposure to MS-222. Most of the decline in total NEFA was due to decreases in saturated fatty acids (14:0, 16:0 and 18:0). The fatty acid displaying the most rapid response to exposure to MS-222 was 20:5n-3. The lower plasma NEFA levels in anesthetized fish may be explained by depressed lipolysis in the presence of the anesthetic.