Alternative Splicing in the Synaptic Protein Interaction Site of Rat Ca v 2.2 (α 1B ) Calcium Channels: Changes Induced by Chronic Inflammatory Pain Sareh Asadi & Mohammad Javan & Abolhassan Ahmadiani & Mohammad Hossein Sanati Received: 1 October 2008 / Accepted: 27 October 2008 # Humana Press 2008 Abstract Voltage-gated N-type Ca 2+ channels play a central role in regulation of neurotransmitter release. The II–III linker of N-type calcium channel α 1B subunit (exons 17–21 in rats) contains synaptic protein interaction (synprint) site, which plays a pivotal role in efficient neurotransmission. Using RT-PCR analysis of rat hippocampus and lumbar spinal cord transcripts, the expressions of Ca v 2.2 exon 18a and a novel Ca v 2.2 splice variant, which were detected in this study, have been investigated, and they showed tissue- specific pattern. The new variant contains a large deletion in II–III linker that produces a stop codon, which is predicted to produce a two-domain-truncated channel. To study the effect of inflammatory pain on the expression pattern of these variants, animals were treated with intraplantar formalin, and the amount of splice variants in lumbar spinal cord was measured. The results showed that chronic inflammatory pain increases the Ca v 2.2 mRNA levels lacking exon 18a and decreases the amount of full-length variants, which do not have any deletion. Determining different Ca v 2.2 splice variants in rat nervous system and the impact of inflamma- tory pain on the splicing pattern suggest a possible regulatory role for calcium channel alternative splicing. Keywords Ca 2+ channels . Alternative splicing . Pain . Spinal cord . Hippocampus . Rat Introduction Voltage-gated calcium channels mediate rapid and voltage- dependent entry of calcium into many types of neural, muscle, and endocrine cells. Calcium entry contributes to a number of physiological functions, including neurotrans- mitter and hormone secretion, muscle contraction, and release of and modulation of other membrane ion channels (Reuter 1983; Tsien 1983). Electrophysiological analysis categorizes native calcium currents into two major classes that differ in their voltage activation properties: high-voltage-activated calcium chan- nels (L-, N-, P/Q- and R-types) and low-voltage-activated calcium channels (T-type; Hofmann et al. 1994). An individual channel is composed of multiple subunits (α 1 , β, α 2 /δ, γ). The α 1 subunit, known as the main pore- forming subunit, determines the major functional properties of the channel (Dunlap et al. 1995). The pore-forming α 1 subunit contains as a basic motif a tetrameric association of four domains each containing a series of six transmembrane α-helical segments, numbered S1–S6, which are connected by both intra- and extracellular loops (Dubel et al. 1992). Ten genes encoding Ca 2+ channel α 1 subunits have been J Mol Neurosci DOI 10.1007/s12031-008-9159-2 Funding: This research was funded by the Neuroscience Research Center, Shahid Beheshti University (M.C.), Tehran, Iran. S. Asadi : A. Ahmadiani Neuroscience Research Center, Shahid Beheshti University (M.C.), Tehran, Iran S. Asadi e-mail: sareh_213@yahoo.com A. Ahmadiani e-mail: aahmadiani@yahoo.com S. Asadi : M. H. Sanati (*) Department of Medical Genetics, National Institute for Genetics Engineering and Biotechnology, P.O. Box 14155-6343, Tehran, Iran e-mail: mhsanati@yahoo.com M. Javan (*) Department of Physiology, School of Medical Sciences, Tarbiat Modares University, P.O. Box 14115-331, Tehran, Iran e-mail: mjavan@modares.ac.ir