Long-lasting recovery of locomotor function in chronic spinal rat following chronic combined pharmacological stimulation of serotonergic receptors with 8-OHDPAT and quipazine

In chronic spinal rats, long-term stimulation of 5-HT receptors with quipazine or 8-OHDPAT by means of daily injection, promotes robust locomotor recovery. The question of a possible potentiation between treatments when applied together was addressed. Daily injections of both 8-OHDPAT and quipazine, were performed for a month in spinal animals. Animals were placed on a treadmill and the bipedal hindlimb locomotion was tested. Motor performances (behavioural test) and locomotor parameters (EMG and kinematic) were analysed weekly during the treatment. Furthermore, the locomotor performances were evaluated during two supplemental months following the end of the treatment. Our results suggest that association of both agonists induced long-lasting positive effects on locomotor function. Motor performances were significantly better after combined injection of both drugs than when the agonists were used separately. But, the most significant and new result is that the locomotor scores did not decrease during the weeks that followed the end of the treatment. These results suggests a long-lasting and 5-HT-dependent reorganisation of spinal networks.