Effects of exogenous melatonin on plasma corticosterone and adrenal glucocorticoid receptor mRNA in neonatal rats

Objective To study the effects of exogenous melatonin on plasma corticosterone (CS) and adrenal glucocorticoid receptor (GR) mRNA in neonatal rats after hypoxic-ischemic brain damage (HIBD).Methods One hundred and forteen 7-day-old Sprague-Dawley rats were randomly divided into four groups: model group (K group),sham operation group (H group),melatonin-treated group (T group),and normal control group (S group).Blood was obtained in different time points after HIBD.Plasma CS levels were measured by radioimmunoassay ( RIA) .The expression of GR mRNA was detected by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR).Results Plasma level of CS increased and the expression of GR mRNA decreased significantly after HIBD,however,these changes were markedly reversed by exogenous melatonin.Conclusions Plasma CS and adrenal gland GR were involved in the pathological process of HIBD.Exogenous melatonin could up-regulate the expression of GR by decreasing the level of endogenous CS,so it may alleviate the excess stress injury after HIBD.