AXONAL SPROUTING IN THE HEMISECTED ADULT-RAT SPINAL-CORD

The morphological and biochemical changes were studied in adult Spragu e-Dawley rats after hemisection at the L(3) spinal cord level. After s urvival periods of one, two and three months, fluorescent tracers, Flu oroGold or rhodamine B, were implanted into the dorsal white columns o f these rats at the positions of the corticospinal tract below the les ion. Following uptake of the tracer, the rats were killed and the moto r cortices and spinal cords of both control and hemisected rats were a nalysed for positively labelled neurons. The highest number of labelle d cells were found two months after hemisection. They were present in both sides of the cortices, particularly in the contralateral cortex, and also in the gray matter of the spinal cord above the hemisection. A few rats which were subjected to complete transection of the spinal cord also showed labelling of neurons in the motor cortex two months a fter lesion. The Protargol silver technique and the [H-3]choline uptak e study confirmed the presence of nerve fibres traversing the lesion s ite in the hemisected spinal cord. Furthermore, when the rats that had been hemisected two months earlier were subjected to a second cut at the same site, chromatolytic neurons were observed in the spinal cord as well as in the motor cortices of both sides. The hemisected rats de monstrated limited recovery in limb movement. The evidence in this stu dy clearly shows that sprouting of nerve fibres has occurred in the le sioned adult rat spinal cord.