A new nicotinic acetylcholine receptor (nAChR) subunit, β4 was identified by screening a rat genomic library. In situ hybridization histochemistry revealed expression of the β4 gene in the medial habenula of adult rat brains. The primary structure of this subunit was deduced from a cDNA clone isolated from a PC12 cDNA library. Functional nAChRs were detected in Xenopus oocytes injected in pairwise combinations with in vitro synthesized RNAs encoding β4 and either the α2, 0, or α4 subunit. Unlike the a3β2 receptor, the α3β4 receptor is not blocked by bungarotoxin 3.1, indicating that the β subunit can affect the sensitivity of neuronal nAChRs to this toxin. These results extend the functional diversity of nicotinic receptors in the nervous system.
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