[Correlation between motor paralysis and neurotoxicity induced by intrathecal dynorphin A (1-17) in rats].

Intrathecal(i.t.) injection of 10 microliters 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 i.t. 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).