Recovery of hindlimb motor functions after spinal cord transection is enhanced by grafts of the embryonic raphe nuclei

In this study, a piece of embryonic tissue from the raphe nucleus was trans planted into the spinal cord below the lesion month after transection. Two months later the recovery of hindlimb motor function in rats which had rece ived a transplant of neural tissue (ST rats) was much better than in spinal control animals without the graft (SC rats), Analysis of the electromyogra phic (EMG) activity showed that the timing of muscle activity during locomo tor-like movement of hindlimbs in ST rats was more regular than in SC rats. In SC rats the relationships between EMG burst duration (soleus, tibialis anterior) and step cycle duration were significantly altered. The restorati on of hindlimb motor function of ST rats was also reflected in the better i nterlimb coordination during locomotor-like hindlimb movements. The results of several behavioural tests demonstrated that the responses to stimulatio n of various receptors, such as tactile or proprioceptive, in ST rats were more complex than in SC rats. Additionally, unlike in SC animals, in ST rat s long-lasting spontaneous episodes of air stepping movement of hindlimbs a ccompanied by a relatively high amplitude of EMC activity were obtained. Th ese results confirm that grafted embryonic raphe nuclei which contain serot oninergic cells are likely to increase the excitability of neuronal circuit ry in the injured spinal cord. Moreover, transplantation of embryonic raphe nuclei encourages the recovery of hindlimb motor function in adult rats ev en when the grafting is carried out several weeks after spinal cold injury.