DEXMEDETOMIDINE, A POTENT ALPHA(2)-AGONIST, DOES NOT AFFECT NEURONAL DAMAGE FOLLOWING SEVERE FOREBRAIN ISCHEMIA IN THE RAT

Central sympathetic activation with increased release of noradrenaline occurs during cerebral ischaemia, but it is not certain how the incre ased sympathetic activity affects neuronal damage. We have studied the effect of dexmedetomidine, a potent alpha(2)-adrenergic receptor agon ist that reduces the central release of noradrenaline, on neuronal dam age after 10 min of severe forebrain ischaemia in the rat. Ischaemia w as achieved by bilateral carotid artery occlusion combined with bleedi ng to a mean arterial pressure of 50 mmHg. The post-ischaemic neuronal damage was most pronounced in the hippocampal CA1 region (median perc entage of necrotic cells 36% (11-69%) and 42% (11-68%) in the dexmedet omidine and vehicle groups, respectively) and in the subiculum. The re ticular thalamic nucleus was moderately damaged in all but one rat, wh ile the rest of the thalamus was almost spared. Most rats had mild to moderate damage in cortex and caudoputamen. Dexmedetomidine did not af fect the neuronal outcome in this model.