The rat cochlear nucleus (CN) is known to receive cholinergic input. To investigate the prevalence of nicotinic acetylcholine receptor (nAChR), immunohistochemistry for alpha4 and alpha7 subunits, which represent nAChRs with high binding affinities for nicotine and alpha-bungarotoxin, respectively, was performed on perfusion-fixed rat brain sections. Microscopic observations and densitometric measurements show dense labeling for alpha7 but not alpha4. Within the CN, alpha7 receptors are found in all subregions, with relatively high densities in granular regions. The distribution of alpha7 within the CN appears to correlate more closely with that of acetylcholinesterase than with mAChR or choline acetyltransferase. Our results suggest a role of nicotinic cholinergic transmission in the rat CN associated with high affinity for alpha-bungarotoxin.