Auditory nerve fibers are the major source of excitation to the three groups of principal cells of the ventral cochlear nucleus (VCN), bushy, T stellate and octopus cells. Shock-evoked EPSCs (eEPSCs) in slices from mice revealed systematic differences between groups of principal cells, indicating that target cells contribute to determining pre- and postsynaptic properties of synapses from spiral ganglion cells. Bushy cells likely to be small spherical bushy cells receive ≤3, most often 2, excitatory inputs; those likely to be globular bushy cells receive ≥4, most likely 5, inputs. T Stellate cells receive 6.5 inputs. Octopus cells receive >60 inputs. The NMDA components of eEPSCs were largest in T stellate, smaller in bushy, and smallest in octopus cells and they were larger in neurons from younger than older mice. The average AMPA conductance of a unitary input is 22 ± 15 nS in both groups of bushy cells, <1.5 nS in octopus cells, and 4.6 ± 3 nS in T stellate cells. Sensitivity to philanthotoxin (PhTX), and rectification in the intracellular presence of spermine indicate that AMPA receptors that mediate eEPSCs in T stellate cells contain more GluR2 subunits than those in bushy and octopus cells. The AMPA components of eEPSCs were briefer in bushy (0.5 msec half-width) than in T stellate and octopus cells (0.8-0.9 msec half-width). Widening of eEPSCs in the presence of cyclothiazide (CTZ) indicates that desensitization shortens eEPSCs. CTZ-insensitive synaptic depression of the AMPA components was greater in bushy and octopus than in T stellate cells.
- brain slice
- Copyright © 2010, Journal of Neurophysiology