Investigation of the effect of isoflurane administration at night or in the day on melatonin levels in rats

Aim: Melatonin synthesis in the pineal gland shows a circadian rhythm and reaches itsmaximum level during the darkness phase. This rhythm is provided by suprachiasmaticnucleus perception of the light-dark cycle. Surgery and anesthesia effects melatonin secretionand endocrine function. The aim of this study is to investigate the effects of isofluraneadministration at night or in the day on melatonin levels in rats.Material and Methods: 15 days old 26 male rats were included and divided into 4 groups byrandomisation. In winter %1.5 isoflurane was administered to the rats in group nightisoflurane (n:7) between 07:00 pm-01:00 am and the rats in group day isoflurane (n:7)between 07:00 am-01:00 pm and 6 L·min-1 of oxygen was administered to the rats in groupnight control (n:6) and group day control (n:6) during the same time periods. At the end of 6hours rats were sacrified after blood samples were taken. Blood samples were centrifuged andplasma melatonin levels were measured by enzyme-linked immunosorbent assay (ELISA).Results: When Group Gc-I (night-isoflurane) was compared with Group Gc-K (nightcontrol),Group Gc-I (night-isoflurane) with Group Gn-I (day-isoflurane), Group Gc-K (nightcontrol)with Group Gn-K (day-control) significant difference was not found on melatoninlevels (sequentially p=0.132, p=0.180, p=0.065). When Group Gn-I (day-isoflurane) wascompared with Group Gn-K (day-control), blood melatonin level was significantly greater inGroup Gn-I (day-isoflurane) (p=0.009).Conclusion: It has been ascertained that %1.5 isoflurane administered during 6 hours in 15days old rats increases melatonin levels significantly in the daytime and does not affect themat nighttime.Keywords: Isoflurane, rat, circadian rhythm, melatonin