Expression of AMPA-type glutamate receptors in pretectal nuclei of the chick brain

Abstract

The pretectum is involved in the neural integration of visually dependent responses. We studied the occurrence of immunoreactivity for subunits that constitute the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type glutamate receptors in the chick pretectum. Four pretectal nuclei of the chick brain, namely, the nucleus pretectalis, the nucleus spiriformis lateralis, the nucleus spiriformis medialis, and the nucleus lentiformis mesencephali, were included in the study, and they all showed AMPA-positive neurons. GluR1- and GluR2/3-positive neurons and fibers were detected in the pretectal nucleus, with GluR4-positive neurons forming a cap surrounding the main core of that nucleus. The lateral spiriform nucleus showed immunoreactivity only for GluR2/3 and GluR4, and the medial spiriform nucleus showed immunoreactivity only for GluR1 and GluR2/3. GluR1-positive neurons and fibers were found in the nucleus lentiformis mesencephali, but only GluR2/3-positive neurons and GluR4-positive fibers were detected into that nucleus. The different patterns of distribution of GluR subunits within the pretectal nuclei suggest different AMPA-triggered properties among their neurons. This suggests that the four pretectal nuclei exert at least part of their functions under control of excitatory glutamate inputs acting through AMPA-type receptors.