Figure 9

Glutamatergic synaptic responses evoked by optic tract stimulation in subnuclei of mouse visual thalamus. A. Examples of synaptic responses in P35 dorsal lateral geniculate nucleus (dLGN) and ventral lateral geniculate nucleus (vLGN) neurons. Synaptic responses in dLGN neurons show all-or-none and larger amplitude excitatory postsynaptic currents (EPSC), whereas vLGN neurons show graded responses with smaller amplitude EPSCs. B. Population data reveal that EPSC amplitudes were smaller in vLGN and progressively increasing stimulus intensity increased peak amplitudes of EPSCs in vLGN but not dLGN. This suggests that while dLGN relay neurons are innervated by only one or two retinal axons, vLGN cells receive smaller inputs from larger numbers of retinal axons. C. Differences in pair-pulse depression (PPD) were observed at retinogeniculate synapses in dLGN and vLGN. An example of synaptic responses recorded in dLGN and vLGN neurons following a train of stimuli with a 25 ms interstimulus interval is shown in C. Examples of current traces showing differences in pair-pulse depression at retinogeniculate synapses in dLGN and vLGN. Synaptic responses recorded in dLGN and vLGN neurons following a train of stimuli with a 50 ms interstimulus interval. D. Average peak EPSC amplitudes in dLGN and vLGN following trains of stimuli (20 Hz, 10 pulses). E. The paired pulse ratio was plotted using the peak EPSC amplitudes following the first and second stimuli. Thus, in addition to exhibiting weaker postsynaptic responses, retinogeniculate synapses in vLGN show weaker paired pulse depression compared to those in dLGN. F. Examples of reconstructions of biocytin-filled relay neurons in dLGN and vLGN.