Flip and Flop Variants of AMPA Receptors in the Rat Lumbar Spinal Cord

The expression of eight messenger RNA splice forms encoding the Flip and Flop variants of AMPA receptor subunits GluR‐A to ‐D in the rat lumbar spinal cord was examined by in situ hybridization using specific oligonucleotides. In the dorsal horn (laminae I, II and III) the predominant mRNA was GluR‐B Flip. Much lower levels of GluR‐A Flip were found in lamina I and in superficial parts of lamina II outer. In the ventral horn, motor neurons expressed mainly GluR‐B Flip, GluR‐C Flip and Flop, and GluR‐D Flip. Serial sectioning through large motor neurons indicated that a given cell contained, for example, both GluR‐C Flip and Flop splice types.