The Phospholipase C-IP3 Pathway is Involved in Muscarinic Antinociception

Abstract

The cellular events involved in muscarinic analgesia were investigated in the mouse hot-plate test. Intracerebroventricular (i.c.v.) pretreatment with antisense oligonucleotides (aODNs) against the a subunit of G q and G 11 proteins prevented the analgesia induced by physostigmine and oxotremorine. Furthermore, administration of the phospholipase C (PLC) inhibitor U-73122, as well as the injection of an aODN complementary to the sequence of PLCb 1 , antagonized the increase of the pain threshold induced by both cholinomimetic drugs. In mice undergoing treatment with LiCl, which impairs phosphatidylinositol synthesis, or treatment with heparin, an IP 3 receptor antagonist, the antinociception induced by physostigmine and oxotremorine was dose-dependently antagonized. I.c.v. pretreatment with TMB-8, a blocker of Ca 2+ release from intracellular stores, prevented the increase of pain threshold induced by the investigated cholinomimetic drugs. Coadministration of Ca 2+ restored the muscarinic analgesia in LiCl, heparin, and TMB-8-preatreated mice. On the other hand, i.c.v. pretreatment with the selective protein kinase C (PKC) inhibitor calphostin C, resulted in a dose-dependent enhancement of physostigmine-and oxotremorine-induced antinociception. The administration of PKC activators, such as PMA and PDBu, dose dependently prevented the cholinomimetic drug-induced increase of pain threshold. Neither aODNs nor pharmacological treatments employed produced any behavioral impairment of mice as revealed by the rota-rod and hole-board tests. These results indicate a role for the PLC-IP 3 pathway in central muscarinic analgesia in mice. Furthermore, activation of PKC by cholinomimetic drugs may represent a pathway of negative modulation of muscarinic antinociception.

Ryanodine receptors are involved in muscarinic antinociception in mice

“…The involvement of InsP 3 R in the mechanism of analgesic action of cholinomimetics has already been observed [9]. Since both receptor subtypes are involved in intracellular calcium mobilization, in the present study the role played by RyRs in muscarinic antinociception was investigated.…”

“…It has been reported that muscarinic antinociception requires the activation of the PLC-InsP 3 pathway. In particular, pretreatment with compounds that inhibit the increase of intracellular Ca 2+ levels through a blockade of InsP 3 R-mediated pathway prevented muscarinic antinociception in mice [9]. However, it should also be taken into account the important role-played by RyRs in the modulation of the intracellular calcium levels.…”

Reversal of NO-induced nociceptive hypersensitivity by St. John’s wort and hypericin: NF-κB, CREB and STAT1 as molecular targets

“…or calphostin C administered 3 h after NO donors and protein expression detected 4 or 6 h after GNT/ SNP. Doses and administration schedules were chosen on the basis of time-course and dose-response curves performed in our laboratory (Galeotti et al 2003).…”

Role of intracellular calcium in acute thermal pain perception

“…administration of heparin, a potent InsP 3 -receptor antagonist (Jonas et al, 1997), produced a dose-dependent hyperalgesic effect indicating the importance of InsP 3 R in the modulation of pain perception. This hypothesis is supported by data indicating that the blockade of InsP 3 R by heparin, as well as the inhibition of InsP 3 production by LiCl, prevented the analgesic effect of cholinomimetic drugs (Galeotti et al, 2003) and delta opioid agonists (Narita et al, 2000). Heparin must be injected into cells or perfused onto permeabilized cells because of its high molecular weight (12 000-13 000 Da) and lack of membrane permeability.…”

“…Antinociception produced by cholinomimetic drugs is prevented by i.c.v. pretreatment with compounds that inhibit the increase of intracellular Ca 2+ levels (Galeotti et al, 2003).…”