Nicotinic receptor distribution in the human thalamus: autoradiographical localization of [ 3H]nicotine and [ 125I] α-bungarotoxin binding

Abstract

The thalamus plays a major role in relaying and transforming information that is relayed to the cortex and in turn modulates cortical outputs. The reticular nucleus projects to the other thalamic nuclei, modulating and integrating their activity. The distribution of high affinity nicotine and α-bungarotoxin ( αBTX) receptors in the human thalamus has been investigated by radioligand autoradiography in post mortem human tissue. [ 3H]nicotine binding in the human thalamus was high in most thalamic nuclei, especially in the lateral dorsal, the medial geniculate, lateral geniculate and anterior nuclei. The distribution of [ 125I] αBTX binding was quite distinct from [ 3H]nicotine binding. [ 125I] αBTX binding was generally lower (<0.26–11.62 fmol/mg protein compared with 6.68–36.17 fmol/mg protein for nicotine binding) and concentrated in the reticular nucleus, with discrete groups of cells displaying higher binding in the latter. These results indicate differences between the distribution of nicotinic receptors in humans and those previously reported in mice and monkeys. Changes in high affinity nicotine and αBTX receptors in the thalamus may contribute to symptoms observed in neuropathological conditions associated with disorders of perception and movement such as Dementia with Lewy Bodies, Alzheimer's Disease and Schizophrenia.