Abstract:
The chemistry of the hamster cochlear nucleus was studied by microdissection of freeze-dried sections combined with microassays. Tissue sample dry weights usually were between 0.1 and 0.5 (mu)g. Amino acid concentrations were measured by high-performance liquid chromatography (HPLC) and activities of enzymes of acetylcholine metabolism by radiochemical procedures. Expressed per dry weight of sample, aspartate concentration was higher in the ventral than in the dorsal cochlear nucleus, whereas glutamate, glutamine, y-aminobutyrate (GABA), taurine, glycine, serine, and alanine concentrations were highest in the molecular layer of the dorsal cochlear nucleus. In general, amino acid concentrations were similar to those in cats and rats. Activity of choline acetyltransferase, the enzyme of synthesis for acetylcholine, was relatively high in granular regions and low in the molecular layer of the dorsal cochlear nucleus, a pattern similar to what has been found in rats and cats. The activity in the anteroventral cochlear nucleus was low compared to the value in rats, however. Activity of acetylcholinesterase, the enzyme of degradation for acetylcholine, was generally lower than in rats and cats, especially in granular regions and the molecular and fusiform soma layers of the dorsal cochlear nucleus. [Work supported by the American Tinnitus Association.]