Autoradiographic localization of nicotinic receptor binding in rat brain using [3H]methylcarbamylcholine, a novel radioligand |
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Authors: | S Yamada D R Gehlert K N Hawkins K Nakayama W R Roeske H I Yamamura |
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Institution: | Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, Japan. |
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Abstract: | Light microscopic autoradiography was used to visualize the neuroanatomical distribution of nicotinic receptors in rat brain using a novel radioligand, 3H]methylcarbamylcholine (MCC). Specific 3H]MCC binding to slide-mounted tissue sections of rat brain was saturable, reversible and of high affinity. Data analysis revealed a single population of 3H]MCC binding sites with a Kd value of 1.8 nM and Bmax of 20.1 fmol/mg protein. Nicotinic agonists and antagonists competed for 3H]MCC binding sites in slide-mounted brain sections with much greater potency than muscarinic drugs. The rat brain areas containing the highest densities of 3H]MCC binding were in thalamic regions, the medial habenular nucleus and the superior colliculus. Moderate densities of 3H]MCC binding were seen over the anterior cingulate cortex, the nucleus accumbens, the zona compacta of substantia nigra and ventral tegmental area. Low densities of 3H]MCC binding were found in most other brain regions. These data suggest that 3H]MCC selectively labels central nicotinic receptors and that these receptors are concentrated in the thalamus, the medial habenular nucleus and the superior colliculus of the rat brain. |
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