Receptor architecture of the macaque lateral geniculate nucleus.

The lateral geniculate nucleus (LGN) is a key thalamic nucleus in the primate visual system that relays visual information from the retina to cortical visual areas. While functional and microanatomical characteristics of the LGN and its layers have been extensively studied, previous investigations on its receptor architecture have been restricted to a small subset of neurotransmitter receptors. To characterise the receptor architecture of the macaque LGN in greater detail, we analysed in vitro autoradiography data to quantify the density of 15 neurotransmitter receptors at the sublayer level, thus improving our understanding of the molecular architecture supporting primate visual function. For comparison, we also determined the densities of these receptors in the primary visual cortex (V1) at a laminar level. Though comparable in shape, the receptor fingeprints of magnocellular layers were larger than those of parvocellular layers. In contrast, receptor fingerprints of cytoarchitectonic layers in V1 differed in both shape and size. Ionotropic/metabotropic and excitatory/inhibitory receptor ratios were significantly larger in V1 than in the LGN, suggesting a greater prominence of inhibitory neurotransmission in the latter region. The nicotinic α4β2 receptor was the only receptor type with a higher density in the LGN compared to V1, highlighting the particular importance of acetylcholine in the modulation of visual stimuli. These findings provide insights into the receptor architecture underlying functions of the LGN, with implications for mechanisms such as visual signal encoding and surround suppression.