Knockdown of the type 2 and 3 inositol 1,4,5-trisphosphate receptors suppresses muscarinic antinociception in mice

Abstract

Several literature reports indicate that supraspinal cholinergic antinociception induced both directly, through muscarinic agonists, and indirectly, by enhancing ACh extracellular levels through cholinesterase inhibitors, is mediated by M 1 receptor stimulation, indicating that M 1 muscarinic receptor subtype plays an essential role in the modulation of pain perception (Bartolini et al., 1992;Iwamoto and Marion, 1993;Ghelardini et al., 1996;Naguib and Yaksh, 1997;Ghelardini et al., 2000). More recently, intracellular mechanisms involved in supraspinal muscarinic antinociception in a condition of acute thermal nociception in normal animals have been investigated. M 1 muscarinic receptors typically couple via the ␣ subunits of the G q/11 family to activate phospholipase C (PLC) (Caulfield and Birdsall, 1998), and the activation of PLC results in hydrolysis of phosphatidyl 4,5-bisphosphate and production of inositol-1,4,5 trisphosphate (IP 3 ) and diacylglycerol (DAG). The main effect of DAG is to activate protein kinase C; IP 3 mediates the release of calcium from intracellular stores by binding to its receptors (Berridge, 1993). The involvement of receptor-mediated activation of the PLC-IP 3 pathway in the increase in pain threshold produced by administration of cholinomimetics was directly demonstrated. The inhibition of the IP 3 synthesis by pretreatment with LiCl, and the blockade of IP 3 receptors (IP 3 R) by administration of the IP 3 R antagonist heparin, dose dependently prevented physostigmine and oxotremorine antinociception (Galeotti et al., 2003).The receptor that recognizes IP 3 was first characterized as a protein called P400 that was enriched in normal cerebella (Mikoshiba et al., 1997); two other types of IP 3 receptors were then cloned. The original IP 3 receptor was named type 1 IP 3 receptor (IP 3 R1), whereas the others were named type 2 IP 3 receptor (IP 3 R2) and type 3 IP 3 receptor (IP 3 R3) (Patel et al., 1999). IP 3 Rs are recognized as a protein family of tetrameric ligand-gated Ca 2ϩ channels that allow mobilization of intracellular Ca 2ϩ stores in response to activation of cell surface receptors linked to IP 3 generation (Berridge, 1993). IP 3 R monomers are large proteins with a calculated molecular mass of about 300 kDa and all three isoforms of IP 3 R share 60 -70% amino acid similarity (Taylor et al., 1999).The aim of the present study was to investigate the role of type 1, 2 and 3 IP 3 Rs in the intracellular mechanism of muscarinic antinociception at a supraspinal level. To this purpose, we inhibited the expression of each IP 3 receptor subtype by using antisense oligonucleotides targeting IP 3 R mRNA sequences that are unique in the mouse genome and therefore assured stringent target selectivity.

An antidepressant behaviour in mice carrying a gene-specific InsP3R1, InsP3R2 and InsP3R3 protein knockdown

“…This observation ruled out the possibility that the antidepressant behaviour showed by InsP3R knockdown animals may have resulted from a sequence-independent action on cerebral structures. The immunoblotting results are in agreement with recent data obtained in our laboratory which demonstrated a widespread cerebral reduction of InsP3R subtypes in knockdown mice (Galeotti et al, 2007). Present results showed that a cortical and hippocampal selective reduction of InsP3R isoforms can be obtained with a aODN concentration at least three times lower than that previously used by us.…”

A Novel Manganese Complex Effective as Superoxide Anion Scavenger and Therapeutic Agent against Cell and Tissue Oxidative Injury

“…15 min before acetic acid injection. Morphine-like analgesic activities of compounds were determined on a hot-plate test . [MnL4] or H 2 L4, dissolved in saline at the same doses, were administered i.p.…”

“…Morphine-like analgesic activities of compounds were determined on a hot-plate test. 45 [MnL4] or H 2 L4, dissolved in saline at the same doses, were administered i.p. 15 min before testing mice reaction time (s) on a hot plate (52.5 °C).…”