BACKGROUND: This study investigated whether brief exposure to nitrous oxide (N(2)O) exacerbates levodopa-induced hyperhomocysteinemia, and if co-treatment with folate or entacapone could reduce total plasma homocysteine (tHcy) levels.

METHODS: Male Wistar rats (N=9 per group) were randomly treated with vehicle/N(2)O (GROUP 1), levodopa/nitrogen (group 2), levodopa/N(2)O (group 3), levodopa/N(2)O+folate (group 4), or levodopa/N(2)O+entacapone (group 5). tHcy was measured at 12 min, 4, 8, and 12 h after anesthesia.

RESULTS AND CONCLUSION: The combination of N(2)O-exposure and levodopa treatment significantly increased tHcy in rats. This hyperhomocysteinemia could be prevented by entacapone but not folate co-administration.