Sympathetic innervation has been demonstrated in bone. Adrenergic stimulation is one of the transmitters of bone loss by uncoupling between decreased bone formation and increased bone resorption.

Objective. - By using a non-specific antagonist of β-adrenergic pathway (propranolol per os), we hypothesized that we could rescue the uncoupling induced mechanical unloading bone loss in the rat model of tail-suspension.

Materials and methods. - Twenty-two female Wistar rats, 12 week-old, have been divided into three groups: eight tail-suspended rats (SR), six tail-suspended rats treated by propranolol (SRP) and eight non-suspended rats (NSR) during 30 days. Bone mineral density (BMD, g/cm²) has been measured by DXA (Hologic QDR-4500A) at D0 and D30 of the study, in the distal femoral metaphysis (DFM), the femoral diaphysis (FD), the whole body (WB, g) and body composition.

Results. - Between D0 and D30, in DFM a significant variation in BMD is observed between NSR and SR (% BMD change: NSR +15.6 ± 3.1% vs SR -1.0 ± 1.4%, P < 0.0001) and BMD rescue in SRP group (% BMD change SRP +5.3 ± 1.5% vs SR -1.0 ± 1.4%, P = 0.03). In FD, gain of BMD is significant in NSR compared to SR (+17.5 ± 1.5% vs +8.2 ± 2.8%, P = 0.007) and to SRP (+17.5 ± 1.5% vs +10.1 ± 2.4%, P = 0.046). Gain in SRP group is not significant compared to SR group (P = 0.6). In WB, SRP gain more BMD than NSR (+14.0 ± 1.8% vs +5.4 ± 0.7%, P = 0.0002) and than SR (+14.0 ± 1.8% vs +7.8 ± 1.4%, P = 0.0043). There is no difference between NSR and SR groups (P = 0.19).

Conclusion. - We demonstrate that β-adrenergic pathway of sympathetic nervous system is a major transmitter pathway of mechanical loading in rat bone. A specific study is necessary to analyse a possible systemic effect of propranolol in rat bone. Propranolol could be used to prevent the induced mechanical unloading bone loss as weightlessness.