Scopolamine impairs eyeblink conditioning in cerebellar LTD-deficient mice

We investigated the effect of the muscarinic acetylcholine receptor (mAChR) antagonist scopolamine on eyeblink conditioning in glutamate receptor subunit 62 null mice, which have severe impairments in cerebellar long-term depression (LTD). Mice were injected intraperitoneally with scopolamine (0.5 mg/kg) or saline, and conditioned using a delay paradigm with tone and periorbital shock but with no overlap between them. The saline-injected mutant mice learned this paradigm normally, as predicted from our previous study. When scopolamine was injected, learning was impaired more severely in the mutant mice than in the wild type mice. Basic sensory and motor performances were not affected. These results suggest that eyeblink conditioning in cerebellar LTD deficient mice depends largely on neural functions susceptible to blocking of mAChRs.