• Hemicholinium-3;
  • Choline acetyltransferase;
  • Acetylcholine;
  • Choline uptake;
  • Ibotenic acid;
  • Kainic acid

Abstract: [3H]Hemicholinium-3 (HC-3) was used to label sodium-dependent, high-affinity choline uptake sites in regions of rat brain. Autoradiography revealed a high density of [3H]HC-3 binding sites in brain regions with a high density of cholinergic terminals, such as the interpeduncular nucleus, caudate-putamen, and olfactory tubercle. This distribution of [3H]HC-3 binding sites was in close agreement with the amounts of choline acetyltrans-ferase in specific nuclei and subregions of rat brain. Destruction of presynaptic cholinergic projections in the cerebral cortex and the basal ganglia by injection of excitotoxins reduced [3H]HC-3 binding by 40–50%. These data indicate that sodium-dependent [3H]HC-3 binding sites are related to the choline transport system present in cholinergic neurons.