Objective     To observe the changes of the expressions of NMDA receptor subunit proteins in the dentate gyrus hippocampus of neonatal rats after ketamine treatment.      Methods     Totally of 24 rats at postnatal day 7 (PND7) were equally divided into instant group (PND7) and 3 weeks post-treatment group (PND28)

and each group was further divided into 3 subgroups

that is

intraperitoneal injection of normal saline (as control

Group C)

intraperitoneal injection of 100 mg/kg ket

amine for 6 h (Group K1)

intraperitoneal injection of 50 mg/kg ketamine for 6 h (Group K2). The rats in PND7 group were killed 24 h after ketamine treatment and the rats in PND28 group were killed 3 weeks after the treatment. Immunohistochemistry was used to detect the expressions of NMDA receptor subunits in the hippocampus dentate gyrus.      Results     Immunohistochemical results showed that in PND7 group

ketamine resulted in elevated expressions of NR2A and NR2B in the hippocampus (

P

<

0.05). In PND28 group

ketamine increased the expression of NR2A subunit protein (

P

<

0.05)

while the expressions of NR2B and NR2C remained unchanged. The dose and administration manner of ketamine seemed have no obvious effects on the expressions of NMDA subunits.      Conclusion      Ketamine could increase the expressions of NMDA receptor subunits in the developmental rat brain and may influence the development of the rat nervous system.