Polyamine inhibition preserves somatosensory evoked potential activity after transient cerebral ischaemia

We tested the hypothesis that the increase in polyamines observed after cerebral ischaemia is related to deficits in electrocortical function as measured by somatosensory evoked potential (SEP). Adult Mongolian gerbils were anaesthetized with ketamine and prepared for monitoring SEP, cerebral blood flow (CBF) in parietal and frontal regions by H2 clearance, and for bilateral carotid artery occlusion (BCO). Seven animals served as controls and received saline. Another 7 animals were treated with the ornithine decarboxylase inhibitor, difluoromethylornithine (DFMO) (100 mg/kg I.P.) just prior to 40 min BCO followed by 4 h reperfusion. With BCO, both CBF and SEP declined significantly. In control animals, CBF fell from basal 37.8 +/- 4.7 cc/100 g/min to 2.9 +/- 1.2 cc/100 g/min and recovered to 22.7 +/- 3.5 cc/100 g/h over the 4 h reperfusion period. DFMO treatment did not alter this CBF pattern. SEP amplitude declined to 11.3 +/- 3.2% basal during occlusion. DFMO preserved SEP during ischaemia (35.5 +/- 16.8% basal) and remained significantly more preserved during reperfusion (p less than 0.05). These results suggest that polyamines are involved in the progressive decline in neuroelectrical function which occurs during occlusion/reperfusion in the Mongolian gerbil. The observation that polyamine inhibition preserves electrical function despite not altering blood flow indicates that the effects of polyamines are not manifested at the level of the vasculature but perhaps at the neuronal membrane.