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

Abstract

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.