AMPA receptor desensitization shapes gain control in the lateral geniculate nucleus

Synaptic short-term plasticity and EPSP summation determine the processing of visual information by dLGN relay cells. In vitro studies suggested that desensitization of AMPA receptor results in pronounced short-term depression in retinogeniculate synapses thereby influencing activation of relay cells by retinal ganglion cell spikes. However, whether retinogeniculate synapses depress and whether AMPA receptors desensitize in vivo is controversial. We here tested the role of AMPA receptor desensitization in processing of visual information by generating a computational model of a dLGN relay cell containing AMPA receptors with different levels of desensitization. In addition, we investigated the in vivo activity of dLGN relay cells in wildtype and CKAMP44-/- mice. CKAMP44 is an auxiliary subunit that increases desensitization of AMPA receptors in retinogeniculate synapses. The comparison of responses of relay cells in the two genotypes therefore allowed us to obtain information about the contribution of AMPA receptor desensitization in processing of visual information. The simulations and the in vivo data show that AMPA receptor desensitization affects relay cell activity by decreasing input gain and response gain. In addition, desensitization sharpens the response of relay neurons to moving gratings in the temporal domain by decreasing the firing rate when the non-preferred stimulus is presented. Altogether, we uncover a complex role of CKAMP44 and AMPA receptor desensitization in information processing of dLGN relay neurons in vivo.