Spinal antiallodynia action of glycine transporter inhibitors in neuropathic pain models in mice.

Abstract

Neuropathic pain is refractory against conventional analgesics, and thus novel medicaments are desired for the treatment. Glycinergic neurons are localized in specific brain regions, including the spinal cord, where they play an important role in the regulation of pain signal transduction. Glycine transporter (GlyT)1, present in glial cells, and GlyT2, located in neurons, play roles in modulating glycinergic neurotransmission by clearing synaptically released glycine or supplying glycine to the neurons and thus could modify pain signal transmission in the spinal cord. In this study, we demonstrated that i.v. or intrathecal administration of GlyT1 inhibitors, cis-N-methyl-N-(6-methoxy-1-phenyl-1,2,3,4-tetrahydronaphthalen-2-yl methyl)amino methylcarboxylic acid (ORG25935) or sarcosine, and GlyT2 inhibitors, 4-benzyloxy-3,5-dimethoxy-N-[1-(dimethylaminocyclopently)-methyl]benzamide (ORG25543) and (O-[(2-benzyloxyphenyl-3-fluorophenyl)methyl]-L-serine) (ALX1393), or knockdown of spinal GlyTs by small interfering RNA of GlyTs mRNA produced a profound antiallodynia effect in a partial peripheral nerve ligation model and other neuropathic pain models in mice. The antiallodynia effect is mediated through spinal glycine receptor alpha3. These results established GlyTs as the target molecules for the development of medicaments for neuropathic pain. However, these manipulations to stimulate glycinergic neuronal activity were without effect during the 4 days after nerve injury, whereas manipulations to inhibit glycinergic neuronal activity protected against the development of allodynia in this phase. The results implied that the timing of medication with their inhibitors should be considered, because glycinergic control of pain was reversed in the critical period of 3 to 4 days after surgery. This may also provide important information for understanding the underlying molecular mechanisms of the development of neuropathic pain.

• Authors: Katsuya Morita, Naoyo Motoyama, Tomoya Kitayama, Norimitsu Morioka, Koki Kifune, Toshihiro Dohi
• Journal: The Journal of pharmacology and experimental therapeutics (J Pharmacol Exp Ther) Vol. 326 Issue 2 Pg. 633-45 (Aug 2008) ISSN: 1521-0103 [Electronic] United States
• PMID: 18448867 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• 4-benzyloxy-3,5-dimethoxy-N-(1-(dimethylaminocyclopently)methyl)benzamide
• Analgesics
• Benzamides
• Glycine Plasma Membrane Transport Proteins
• Receptors, Glycine
• Slc6a5 protein, mouse
• Slc6a9 protein, mouse
• glycine receptor alpha3 subunit

Topics

• Analgesics (chemistry, pharmacology, therapeutic use)
• Animals
• Behavior, Animal (drug effects)
• Benzamides (pharmacology)
• Blotting, Western
• Diabetes Mellitus, Experimental (complications, physiopathology)
• Diabetic Neuropathies (drug therapy, etiology, metabolism, physiopathology)
• Disease Models, Animal
• Glycine Plasma Membrane Transport Proteins (antagonists & inhibitors, biosynthesis)
• Hyperalgesia (drug therapy, etiology, metabolism)
• Male
• Mice
• Mice, Inbred Strains
• Receptors, Glycine (antagonists & inhibitors, biosynthesis)
• Sciatic Neuropathy (drug therapy, metabolism, physiopathology)
• Spinal Cord (drug effects, metabolism)