Choline acetyltransferase in cochlear root neurons

Cochlear root neurons are a distinct group of cells located in the auditory nerve root in small rodents. Their transmitter is still unknown. Some of our preparations showed immunoreactivity of somata of cochlear root neurons with both polyclonal and monoclonal antibodies against choline acetyltransferase (ChAT) which, despite their very weak histochemical reaction for acetylcholinesterase (AChE), suggested that cochlear root neurons might be cholinergic. To test this, we used a radiometric assay to measure ChAT activities of rat auditory nerve root samples containing cochlear root neurons and of adjacent samples not containing them. There was no significant difference between the low mean ChAT activities of these two groups of samples. Thus, cochlear root neurons are not likely to be cholinergic.