The ventral nucleus of the lateral lemniscus (VNLL) provides a major
inhibitory projection to the inferior colliculus (IC). Neurons in the VNLL
respond with various firing patterns and different temporal precision to
acoustic stimulation. The present study investigates the underlying intrinsic
and synaptic properties of various cell types in different regions of the
VNLL, using in vitro electrophysiological recordings from acute brain slices
of mice and immunohistochemistry. We show that the biophysical membrane
properties and excitatory input characteristics differed between dorsal and
ventral VNLL neurons. Neurons in the ventral VNLL displayed an onset-type
firing pattern and little hyperpolarization-activated current (Ih).
Stimulation of lemniscal inputs evoked a large all-or-none excitatory response
similar to Calyx of Held synapses in neurons in the lateral part of the
ventral VNLL. Neurons that were located within the fiber tract of the lateral
lemniscus, received several and weak excitatory input fibers. In the dorsal
VNLL onset-type and sustained firing neurons were intermingled. These neurons
showed large Ih and were strongly immunopositive for the hyperpolarization-
activated cyclic nucleotide-gated channel 1 (HCN1) subunit. Both neuron types
received several excitatory inputs that were weaker and slower compared to
ventrolateral VNLL neurons. Using a mouse model that expresses
channelrhodopsin under the promotor of the vesicular GABA transporter (VGAT)
suggests that dorsal and ventral neurons were inhibitory since they were all
depolarized by light stimulation. The diverse membrane and input properties in
dorsal and ventral VNLL neurons suggest differential roles of these neurons
for sound processing