Dopaminergic neurotransmission triggers ischemia-induced hyperactivity in Mongolian gerbils

It is recognized that sustained ischemia-induced hyperactivity is related to abnormalities in dopamine function. However, it is unclear that dopaminergic neurotransmission triggers such ischemia-induced hyperactivity. Therefore, the relationship between dopaminergic neurotransmission and ischemia-induced hyperactivity was investigated in an animal model using Mongolian gerbils. When haloperidol 2 mg/kg was administered i.p. 30 min after ischemia, the ischemia-induced hyperactivity at 24 h after ischemia was blocked. General behavior was similar to that of sham-operated animals. Haloperidol at doses of 0.1 and 0.2 mg/kg had no effect on locomotor activity in sham-operated animals and decreased ischemia-induced hyperactivity when the drug was administered 24 h after ischemia; these doses did not have any effect on ischemia-induced hyperactivity when the drug was administered 30 min after ischemia. On the other hand, when the animal was confined to a small, restrictive cage for the 24 h period immediately following ischemic injury, locomotor activity at 24 h after ischemia increased. Such behavior also increased in animals when they were returned to their original more permissive cages immediately after ischemia. It is conceivable that the decrease in the level of activity was not related to ischemia-induced hyperactivity. These data suggested that the inhibition of ischemia-induced hyperactivity can be induced by complete blockage of dopaminergic receptors immediately after ischemia.