Effect of acute administration of potassium channel blockers on the behavioral symptoms of Parkinsonism induced by 6-hydroxydopamine in rat

4-aminopyridine (4-AP) and tetraethylammonium (TEA) are two potassium channel blockers which have shown that have beneficial effects in treating some neurological disorders such as ataxia, Alzheimer and multiple sclerosis. In this study the effect of acute administration of 4-AP and TEA in the treatment of behavioral symptoms of Parkinsonism induced by the toxin 6-hydroxydopamine (6-OHDA) was studied in male rats. 6-OHDA was injected into left medial forebrain bundle (MFB) by stereotaxic surgery using Hamilton syringe. Then, in the third week after surgery, the rats before and after drug application were tested for rotational behavior induced by apomorphine. In the fourth week, Rotarod test was performed in the presence of the blockers for six consecutive days. 4-AP at doses 200 and 500 µg/kg had no significant effect, but at dose 1000 µg/kg led to a significant improvement of behavioral symptoms of Parkinsonism in the rotation test. On the other hand, the drug decreased motor performance and motor learning in the Rotarod test. TEA at dose 1 mg/kg was ineffective, but at dose 2 mg/kg caused a significant decrease, and at dose 5 mg/kg caused a significant increase in the number of rotations of the Parkinsonian rats. TEA had no effect on the motor learning in the Rotarod test. The results of this study indicate that 4-AP and TEA, in a dose-dependent manner, weaken some symptoms of Parkinsonism, but worsen some other symptoms.