The hyperkinetic features of the Huntington's disease are due to the loss of:

Corpus striatum sends inhibitory input to globus pallidus (external); globus pallidus is reciprocally connected with subthalamic nucleus. In Huntington's disease there is loss of (inhibitory) GABAergic and cholinergic neurons of the striatum. Loss of dopaminergic neurons in the nigrostriatal tract will lead to Parkinson's disease. Huntington's disease is a trinucleotide repeat disorder with multiple CAG repeats.