KA1-like kainate receptor subunit immunoreactivity in neurons and glia using a novel anti-peptide antibody

Functional kainate receptors can be formed by various combinations of subun its with low (GluR5, GluR6 and GluR7) or high affinity (KA1 and KA2) for ka inate. The precise contribution of each subunit to native receptors, as wel l as their distribution within the central nervous system (CNS) is still un clear. Here, we describe the presence of KA1-like immunoreactivity in both neurons and glial cells of the CNS, using a newly developed antiserum to a specific carboxy terminus epitope of the KA1 subunit. Intense immunoreactiv ity was observed in the CA3 area of the rat hippocampus. Electron microscop y revealed that immunostaining was present in dendritic structures postsyna ptic to commissural-associational fibers, rather than in those contacted by mossy fiber terminals. We also observed immunostaining of CA1 pyramidal ce ll apical dendrites. In the cerebral cortex, KA1-like immunostaining was ob served in many pyramidal neuron somata, mainly in layer V, and along their apical dendrites. A subset of gamma-amino-butyric acidic cells were also in tensely stained. In the cerebellum, the antiserum selectively stained Purki nje cell somata and their dendrites as well as Bergmann glial processes. Ot her types of macroglia were also labeled by the KA1 antiserum. Thus, optic nerve oligodendrocytes both in vitro and in situ and cultured astrocytes we re densely stained. Our results indicate that KA1-type subunits are more wi dely distributed throughout the CNS than previously thought. This newly dev eloped antiserum may help to clarify the properties of kainate recepters co ntaining KA1 or KA1-type subunits within the normal and pathological brain. (C) 2000 Elsevier Science BN. All rights reserved.