Kir6.2 oligoantisense administered into the globus pallidus reduces apomorphine-induced turning in 6-OHDA hemiparkinsonian rats

ATP-sensitive inwardly rectifying potassium channels (KATPs) couple cell me tabolism with its membrane potential. The best characterized KATP is the pa ncreatic KATP which is an heteromultimer of Kir6.2 and SUR1 protein subunit s. KATPs are found in a variety of excitable cells, including neurons of th e central nervous system. Basal ganglia (BG), especially in the substantia nigra (SN) reticulata and the globus pallidus (GP), have a high density of KATPs. Pharmacological modulation of the KATPs within the BG alters GABAerg ic activity and produces behavioural changes. However, the relatively high concentrations of drugs used might not have been entirely selective for the KATPs and may have acted at presynaptic nerve terminals as well as on the post-synaptic neurons. As an alternative means of examining the role of KAT Ps in regulating motor behavior, we used oligoantisense technology to dimin ish selectively Kir6.2 formation in the GP neurons. We then examined the ef fect of reduction in Kir6.2 expression on apomorphine-induced turning behav ior in rats with unilateral 6-hydroxydopamine (6-OHDA) lesions of the SN. T wo weeks after injection of 6-OHDA, contralateral circling in response to a pomorphine (0.25 mg/kg sc) was recorded. Kir6.2 antisense oligodeoxyribonuc leotide (ODN) was then administered daily for 6 days into the GP ipsilatera l to the 6-OHDA injection. Responses to apomorphine were then tested again and the animals killed to determine the effect of the antisense ODN on Kir6 .2 mRNA. Administration of Kir6.2 antisense ODN significantly attenuated ap omorphine-induced contralateral turning and specifically reduced Kir6.2 mRN A in the injected GP. These results are consistent with pharmacological exp eriments which suggest that KATP channels in the GP are involved in motor r esponses to apomorphine in 6-OHDA lesioned rats, localizing the effects to the GP neurons, probably through modulation of the GABAergic system. (C) 19 99 Elsevier Science B.V. All rights reserved.