CORRELATION BETWEEN MOTOR PARALYSIS AND NEUROTOXICITY INDUCED BY INTRATHECAL DYNORPHIN A(1-17) IN RATS

Intrathecal(it) injection of 10 μl of dynorphin A(1-17) 20 nmol· L^-1 per rat resulted in irreversible hind limb paralysis and suppression of the tail flick reflex lasting for up to 40 h. The dual effects of dynorphin appeared 5～10 min after the it administration. Histologic examination of the spinal cord in the rats demonstrated dead and/or dying and degenerated motor-neurons in the ventral horn located predominately in the lumbar segment(a 87.2% reduction of the number of motor neurons,P<0.01) and also in a lesser degree in sacral segment(-69.6%,P<0.05). The thoracic segment was essentially normal(-8.2%,P>0.05).