Differential distribution of voltage‐gated calcium channel alpha‐2 delta (α2δ) subunit mRNA‐containing cells in the rat central nervous system and the dorsal root ganglia

Abstract Voltage‐gated calcium channels (VGCCs) play an essential role in controlling neurotransmitter release, neuronal excitability, and gene expression in the nervous system. The distribution of cells that contain mRNAs encoding the auxiliary α 2 δ‐1, α 2 δ‐2, and α 2 δ‐3 subunits of the VGCCs in the central nervous system (CNS) and the dorsal root ganglia (DRG) was examined in rats by using in situ hybridization. Specific labeling of α 2 δ‐1, α 2 δ‐2, and α 2 δ‐3 mRNAs appeared to be largely confined to neurons and was widely, although differentially, distributed in the brain, the spinal cord, and the DRG. Importantly, α 2 δ‐2 mRNA was found to be expressed in interneurons in the cortex, the hippocampus, the striatum, and in regions that contain dense cholinergic neurons. Our results suggest that different α 2 δ subunits may exert distinctive functions in the CNS. The α 2 δ‐1 subunit mRNA is localized in brain regions known to be involved in cortical processing, learning and memory, defensive behavior, neuroendocrine secretion, autonomic activation, primary sensory transmission, and general arousal. The α 2 δ‐2 subunit mRNA is present in brain regions known to modulate the overall activities of the cortex, the hippocampus, and the thalamus. The α 2 δ‐2 subunit is also found in brain regions known to be involved in olfaction, somatic motor control, fluid homeostasis, ingestive and defensive behaviors, neuroendocrine functions, and circadian rhythm. In addition to being localized in brain regions that express α 2 δ‐1 and α 2 δ‐2 subunit mRNAs, α 2 δ‐3 subunit mRNA is highly expressed in regions involved in auditory information processing and somatic movement. J. Comp. Neurol. 491:246–269, 2005. © 2005 Wiley‐Liss, Inc.