The synaptic connection from rat lateral posterior thalamic nucleus to primary visual cortex is an important part of extrageniculate visual pathway. The short-term plasticity of this synaptic transmission is investigated in vivo by using field potential recording and iontophoresis methods. The field potentials were depressed rigorously by either paired-pulse stimulation or repetitive stimulation at different frequency (10, 20, 50 Hz). Iontophoresis of bicuculline and 2-hydroxy-saclofen decreased the depression degree, while iontophoresis of Ca²⁺ increased the depression degree. Therefore, the short-term plasticity of synaptic transmission in this pathway is affected by many factors, such as: changing the transmitter release level at pre-synaptic terminal and activity of GABAergic receptors. However, when applying APV, the selective antagonist of NMDA receptors, no any obvious change in short-term synaptic plasticity was obtained. The rigorous short-term plasticity in this visual pathway may play a role in the visual attention function, which is related to the lateral posterior thalamic nucleus.