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.
ASJC Scopus subject areas
- General Biochemistry, Genetics and Molecular Biology
- Pharmacology, Toxicology and Pharmaceutics(all)