Patterns of GABABR1a,b receptor gene expression in monkey and human visual cortex

Abstract

In situ hybridization histochemistry and immunocytochemistry were used to examine GABABR1a,b receptor mRNA and protein expression in areas 17 and 18 of the visual cortex of normal macaque monkeys and of monkeys that had been deprived of vision in one eye. In addition, the normal patterns of GABABR1a,b protein expression were immunocytochemically studied in the human visual cortex. Overall levels of GABABR1a,b transcript were higher in area 17 than in area 18. In area 17 GABABR1a,b mRNA levels were highest in layers IVC and VI, moderate in layers II-IVA and low in layers I, IVB and V. In area 18 GABABR1a,b transcript expression was high in layers II and III, moderate in layers IV and VI and low in layers I and V. Immunocytochemistry revealed nearly identical patterns of GABABR1a,b protein expression in areas 17 and 18 in monkey and human. Both pyramidal and non-pyramidal neurons were GABABR1a,b immunoreactive. The majority of intensely immunoreactive neurons in layers II, III, V and VI were pyramidal cells. Numerous non-pyramidal cells were intensely immunoreactive in layer IV of area 17 but layer IV cells were only lightly immunoreactive in area 18. Following 10 day periods of monocular deprivation, induced by intravitreal injections of tetrodotoxin, levels of GABABR1a,b mRNA and protein were decreased in the deprived eye dominance columns of layers IVC and VI.