Cholinergic modulation of stellate cells in the mammalian ventral cochlearnucleus

The main source of excitation to the ventral cochlear nucleus (VCN) Is from glutamatergic auditory nerve afferents, but the VCN is also innervated by two groups of cholinergic efferents from the ventral nucleus of the trapezo id body. One arises from collaterals of medial olivocochlear efferents, and the other arises from neurons that project solely to the VCN. This study e xamines the action of cholinergic inputs on stellate cells in the VON. T st ellate cells, which form one of the ascending auditory pathways to the infe rior colliculus, and D stellate cells, which Inhibit T stellate cells, are, distinguished electrophysiologically. Whole-cell recordings from stellate cells In slices of the VCN of mice demonstrate that most T stellate cells a re excited by cholinergic agonists through three types of receptors, wherea s all D stellate cells tested were Insensitive to cholinergic agonists. Nic otinic excitation in T stellate cells has two components. The faster compon ent was blocked by alpha -bungarotoxin and methyllycaconitine, suggesting t hat receptors contained alpha7 subunits; the slower component was insensiti ve to both. Muscarinic receptors excite T stellate cells by blocking a volt age-insensitive, "leak" potassium conductance. Our results suggest that cho linergic efferent innervation enhances excitation by sounds of T stellate c ells, opposing the inhibitory action of cholinergic innervation in the coch lea that is conveyed indirectly through the glutamatergic afferents. The in hibitory action of D stellate cells on their targets is probably not affect ed by cholinergic inputs. Excitation of T stellate cells by cholinergic, ef ferents would be expected to enhance the encoding of spectral peaks In nois e.