RECOVERY OF LOCOMOTOR-ACTIVITY IN THE ADULT CHRONIC SPINAL RAT AFTER SUBLESIONAL TRANSPLANTATION OF EMBRYONIC NERVOUS CELLS - SPECIFIC ROLEOF SEROTONERGIC NEURONS

Locomotor movements are programmed in a specialised neuronal network t hat is localised in the central nervous system and referred to as the central pattern generator (CPG) for locomotion. This CPG can be activa ted by pharmacological agents such as monoamines. The aim of the prese nt study was to try to activate the CPGs by using cells that are suppo sed to release serotonin locally. Adult chronic spinal rats were injec ted with embryonic brainstem neurons within the spinal cord under a th oracic transection. This procedure resulted in a monoaminergic reinner vation of the lumbar enlargement. With the help of a specific neurotox in for noradrenergic neurons (6-hydroxydopamine), it was possible to i solate the serotonergic system. After such transplantation of monoamin ergic neurons and even with serotonergic neurons alone, a bilateral, a lternating, rhythmic locomotor-like activity recovered in hindlimbs. F urthermore, this locomotor-like activity was clearly facilitated when the re-uptake of serotonin was blocked by zimelidine. Therefore, we co nclude that transplanted embryonic serotonergic neurons are able to ac tivate the CPG for locomotion.