Abstracts

RATIONALE:_Despite the important role of NMDA receptor signaling during epilepsy, little is known about NMDA receptors in interneurons. This study characterizes the distribution and development of alpha-actinin-2 (AA2), an actin binding protein implicated in NMDA receptor localization, in hippocampal interneurons. METHODS:_Rat brain sections were used for double immunofluorescence labeling experiments. Light microscopy was used to compare somatic AA2 immunoreactivity with various interneuron markers in the dentate gyrus and CA1. Rats were also examined after fluid percussion injury (FPI) performed under anesthesia as described previously (Toth et al, 1997). RESULTS:_AA2 is expressed throughout the hippocampus with high levels observed in the dendrites of granule cells, CA2 and scattered cells throughout the dentate gyrus and CA1. All the highly AA2 immunoreactive non-principal cells in the dentate gyrus and CA1 are labeled by GAD67 (99%) indicating that they are GABAergic interneurons. The majority of these AA2 immunoreactive neurons are neuropeptide Y-positive. AA2 immunoreactivity is present in the hippocampus at P1, interneuron immunoreactivity appears at P7 and the adult staining pattern is seen by P21. AA2 examined after FPI revealed no differences in the number of highly immunoreactive interneurons between injured and control animals. CONCLUSIONS:_The major finding of this study is that alpha-actinin-2 is present in hippocampal interneurons. The specific expression of AA2 in the neuropeptide Y-positive interneurons indicates a possible role in NMDA receptor signaling.