Effects of neonatal dexamethasone or methylprednisolone on rat growth and neurodevelopment

Background: Clinical studies have demonstrated that premature infants receiving long-term dexamethasone therapy have reduced linear growth, decreased weight gain, and smaller head circumferences. The purpose of the present study was to investigate the effects of the same equivalent doses for anti-inflammatory potency of neonatal dexamethasone and methylprednisolone on rat growth and neurodevelopment. Methods: The pups were randomly separated into three treatment groups on postnatal day (PD) 3. At postnatal 3-5 days, tapering doses of corticosteroids or sterile saline were administered subcutaneously. Group 1 was the dexamethasone group (n = 12; PD 3, 0.5 mg/kg; PD 4, 0.25 mg/kg; PD 5, 0.125 mg/kg; PD 6, 0.05 mg/kg s.c.); group 2, methylprednisolone group (n = 12; PD 3, 2.6 mg/kg; PD 4, 1.3 mg/kg; PD 5, 0.650 mg/kg; PD 6, 0.325 mg/kg; group 3, control group (n = 12; normal saline injected). Weight was recorded on PD 3-6, 8, 14, 22, length was recorded on PD 3, 7, 14, 21 for each group. Neurological responses and physical development were tested on PD 7, 14, 21. Results: On PD 4-6, 8, 14, 22 the weight in the dexamethasone and methylprednisolone groups was lower than in the control group, but the weight in the dexamethasone group was the lowest (P < 0.05). The length in the dexamethasone group was significantly shorter than in the methylprednisolone group on PD 14 and 21. Dexamethasone-treated animals had a reduced total neurological score compared with the methylprednisolone and control groups on PD 7, 14, 21. Although methylprednisolone-treated animals had lower total neurological score than that of the control group on PD 7 and PD 14 (P < 0.05), total neurological scores were not different in the methylprednisolone and control groups on PD 21. Conclusions: Postnatal methylprednisolone treatment might be safer than dexamethasone treatment in newborns.