In the visual system, the afferent axons from the dorsal lateral geniculate nucleus (dLGN) to the primary visual cortex (V1) show significant activity-dependent plasticity in early postnatal life. To determine whether activity-dependent plasticity operates also in feedback projections from V1 to dLGN, we inactivated cortical inputs pharmacologically and examined possible changes in the density of synaptic proteins, vesicular glutamate transporter 1 (VGluT1) and type 1 metabotropic glutamate receptor alpha (mGluR1alpha), which locate pre- and postsynaptically at feedback projections, respectively in dLGN of rats. The intensity of the immunohistochemical signal of mGluR1alpha in dLGN significantly decreased following the cortical inactivation for at least 2 days, and the decrease was maintained under cortical inactivation until 28 days. On the other hand, the signal intensity of VGluT1 showed a significant increase following 14 or 28 days of cortical inactivation. In adult rats, however, we found no significant change in VGluT1 signal intensity and only a small and transient downregulation of mGluR1alpha following 7-day inactivation. Thus, the decrease in presynaptic activity induces a rapid downregulation of postsynaptic mGluR1alpha followed by a delayed upregulation of presynaptic VGluT1 in young rats. These results suggest that feedback synapses are regulated by neural activity during development.