Cellular localization of serotonin(2A) (5HT(2A)) receptors in the rat brain.

The serotonin(2A) (5HT(2A)) receptors have been shown to play an important role in several psychiatric disorders, including depression, schizophrenia, and alcoholism. This immunohistochemical study examined the cellular localization of 5HT(2A) receptors in various rat brain structures (olfactory, striatum, cortex, hippocampus, and amygdala). The colocalization of 5HT(2A) receptors in astrocytes was performed by double-immunofluorescence staining of 5HT(2A) receptors and of glial fibrillary acidic protein (GFAP) using confocal laser microscopy. 5HT(2A) receptor immunolabeling was observed in olfactory bulbs, neostriatum, hippocampus, amygdala, and neocortex. Somata and dendrites of pyramidal cells in the frontal cortex (layer V) were densely labeled with 5HT(2A) receptors. In several other brain structures (hippocampus, amygdala, striatum, olfactory structures), 5HT(2A) receptor immunolabeling was found in cell bodies and processes of neurons. 5HT(2A) receptor immunolabeling was also observed in GFAP-positive cells of the various brain structures we investigated (layers I/VI of the neocortex, corpus callosum, hippocampal fissure and hilus, and amygdala). These results indicate that 5HT(2A) receptors are expressed in neurons and astrocytes and suggest the possibility that not only neuronal but also glial 5HT(2A) receptors have functional implications in psychiatric disorders.