Study on the in vivo regulatory role of glutamate in osteoblast (OB) and osteoclast (OC) differentiation is less advanced. The present study investigated the effect of dextromethorphan (DXM), an N-methyl-D-aspartate receptors (NMDARs) antagonist, on osteoporosis development.Main methods:
In order to examine the role of glutamate in bone metabolism, ovariectomized (Ovx) female Wistar rats were injected three times per week for 8 weeks with either saline, or 15 μg/kg of β-estrodiol, or DXM (40 mg/kg) intraperitoneally. Serum samples were collected every two weeks for measuring osteocalcin and C-terminal telopeptide of type I collagen (CTX-1) level. Rats were then sacrificed at week 8 and the femurs harvested for micro-CT scanning and mechanical strength.Key findings:
In saline-treated group, osteocalcin level significantly lower than that of sham-operated rats at 8 weeks after operation, while CTX-1 levels were not affected. Estrogen treatment, as a positive control, partially inhibited the Ovx-induced reduction of osteocalcin serum level. DXM injection prevented the Ovx-induced reduction of osteocalcin expression and significantly upregulated CTX-1 expression. The micro-CT scan showed that the bone volume density decreased significantly in DXM treated rats compared to the sham-operated rats. In the mechanical strength assay, the maximum failure load for DXM treatment was significantly lower than the other groups.Significance:
Treatment with DXM upregulated OB and OC markers in Ovx rats, however with a greater effect on the OC marker, and had no significant benefit on bone volume density or bone strength.