Blockade of fast A-type and TEA-sensitive potassium channels provide an antiparkinsonian effect in a 6-OHDA animal model.

OBJECTIVE: To evaluate the effect of K+ channels inhibitors in treatment of parkinson`s disease (PD). METHODS: This prospective comparative study was conducted in the Qazvin University of Medical Sciences, Iran, from April 2015 to January 2016. Male rats (n=37) received intraperitoneal doses of TEA (2 and 5 mg/kg) or 4-AP (0.5 and 1 mg/kg) twice-daily, before a stereotactic injection of 6-hydroxydopamine (6-OHDA) for the following 7 days. The 6-OHDA was injected into right medial forebrain bundle (MFB) of the rat brains. Development and severity of PD were assessed using the apomorphine-induced rotational test, the elevated body swing test and rotarod tests. Concentration of malondialdehyde (MDA), a marker of oxidative stress, was measured in rat sera. RESULTS: Tetraethylammonium and 4-AP significantly reduced the number of apomorphine-induced rotations and improved motor learning in the rotarod test at both doses. Administration of 4-AP and TEA together was more effective than single administration of either agent. Malondialdehyde measurement showed that pretreatment with TEA could not prevent 6-OHDA-induced oxidative stress. CONCLUSION: Our results showed that pretreatment with TEA and 4-AP has a neuroprotective effect against 6-OHDA in dopaminergic neurons in the substantia nigra.

Pretreatment with potassium channel blockers of 4-aminopyridine and tetraethylammonium attenuates behavioural symptoms of Parkinsonism induced by intrastriatal injection of 6-hydroxydopamine; the role of lipid peroxidation.

OBJECTIVES: Potassium channels participate in cellular and molecular signalling pathways regulating the life and death of neurons. In this study, effect of pretreatment with potassium channel blockers of 4-aminopyridine (4-AP) and tetraethylammonium (TEA) on the behavioural symptoms of 6-hydroxydopamine (6-OHDA)-induced Parkinsonism was evaluated. METHODS: 6-OHDA was injected into right striatum of adult male Wistar rats using stereotaxic surgery. Severity of 6-OHDA-induced Parkinsonism was assessed by conventional behavioural tests. 4-AP and TEA were injected twice per day intraperitoneally, before 6-OHDA injection to 15 days after that. Also, malondialdehyde (MDA) concentration as a marker of oxidative stress was measured in rat sera. RESULTS: Pretreatment with 4-AP (0.5 and 1 mg/kg) and TEA (2 and 5 mg/kg) attenuated significantly behavioural symptoms of 6-OHDA-induced Parkinsonism. Application of both 4-AP and TEA together was more effective than the effect of each one of these blockers alone. 6-OHDA increased MDA concentration but pretreatment with 4-AP prevented of 6-OHDA-induced increase in MDA. On the other hand, pretreatment with TEA and combination of TEA and 4-AP could not prevent of 6-OHDA-induced oxidative stress. DISCUSSION: Since severity of behavioural symptoms of 6-OHDA-induced Parkinsonism is correlated to the degree of nigral dopaminergic cell death, we suggest that antiparkinsonism effect of TEA and 4-AP was mediated by their neuroprotective effect. Because, both Parkinsonism in rat and PD in human, the main pathophysiological hallmark, is neurodegeneration of dopaminergic neurons in substantia nigra, we suggest doing clinical trials for evaluation of effectiveness of 4-AP and TEA in slowing down of PD progress.