Effect of isotonic contrast agents on spinal reflexes in the cat

The effects of isotonic solutions of three contrast agents, administered intrathecally, were studied in cats. A pronounced increase in the electrically evoked cortico-spinal responses and segmental spinal polysynaptic reflexes was recorded after administration of methylglucamine diatrizoate. Injection of methylglucamine iothalamate resulted in an increase of the amplitudes of these reflexes, while metrizamide did not show any consistent effect. The data suggest that water-soluble media have direct effects upon spinal gray matter.