INTERSTITIAL AND TISSUE CATIONS AND ELECTRICAL POTENTIAL AFTER EXPERIMENTAL SPINAL-CORD INJURY

Interstitial and tissue cations and electrical potential were studied in an experimental model of spinal cord contusion injury in anaestheti sed cats. Measurements of interstitial ion activity in the grey matter at the injury site (with ion-selective electrodes), showed a decrease of sodium and calcium, an increase of potassium, a small acidificatio n and a negative shift in the electrical potential 5 min after injury. The interstitial ionic changes were completely reversible within 90 m in following injury. Measurements of the ion content in a tissue sampl e from the injury site (flame photometry) showed an increase of sodium and calcium and a decrease of potassium 5 min after injury. The magni tude of the post-injury sodium change was much larger than the potassi um change, both for interstitial and tissue measurements. Treatment of the animals with the calcium entry blocker flunarizine before the inj ury did not influence the magnitude of post-injury interstitial calciu m decrease but significantly increased the rate of subsequent recovery . Pre-injury flunarizine treatment also significantly increased the re covery rate of the electrical potential. The experiments suggest the o ccurrence of a net ionic shift towards the intracellular space, which may contribute to oedema formation in the very early post-injury perio d. The post-injury decrease of interstitial calcium activity is probab ly not mediated by flunarizine-sensitive calcium entry mechanisms; suc h mechanisms may, however, be involved in the subsequent recovery peri od for interstitial calcium activity. Calcium ions may be involved in the recovery process of the negative electrical potential after injury .