Alteration of GABAergic and glycinergic mechanisms by lidocaine injection in the rostral ventromedial medulla of neuropathic rats

Nayef E. Saadé, Hassen Al Amin, Sima Tchachaghian, Suhayl J. Jabbur, Samir F. Atweh

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Attenuation of neuropathic manifestations in experimental animals, by lidocaine injection in the rostral ventro-medial medulla (RVM), has been traditionally attributed to selective block of a descending pain facilitatory system. However, the presence of descending fibers carrying this effect and the selective action of lidocaine on the facilitatory neurons, have not been supported by convincing experimental evidence. The present study aimed to investigate the mechanisms underlying the hypoalgesic action of lidocaine injection in the brainstem. Several groups of rats were subjected to mononeuropathy on their left hind paws, according to the model of spared nerve injury, and were subsequently implanted with guide cannulae in the RVM. After recovery, rats received injections of lidocaine, GABA and glycine agonists or antagonists and their effects were assessed on behavioral tests of allodynia and hyperalgesia. Injections of lidocaine at doses ranging between 0.05% and 2% produced attenuation at high doses and no effects or increasing hyperalgesia at low doses. GABA and glycine agonists increased neuropathic manifestations while their antagonists elicited the opposite effects. A combined injection of GABA agonist or glycine with lidocaine (0.5%) prevented the inhibitory effects of lidocaine injection alone. Our results are in line with the abundant documentation on the alteration of the function of inhibitory neurons by lidocaine and reveal a possible action of the injected high doses on the GABAergic and glycinergic neurons in the RVM. The resulting block of the inhibitory tone exerted by these neurons can lead to a release of the descending pain inhibitory systems.

Original languageEnglish
Pages (from-to)89-99
Number of pages11
JournalPain
Volume149
Issue number1
DOIs
Publication statusPublished - Apr 2010
Externally publishedYes

Fingerprint

Lidocaine
Injections
GABA Agonists
Hyperalgesia
Glycine
Neurons
Mononeuropathies
GABA Antagonists
Pain
GABAergic Neurons
Documentation
Brain Stem
Wounds and Injuries

Keywords

  • Allodynia
  • Descending inhibition
  • Hyperalgesia
  • Lidocaine-neurotoxicity
  • Pain modulation

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine
  • Clinical Neurology
  • Neurology
  • Pharmacology

Cite this

Alteration of GABAergic and glycinergic mechanisms by lidocaine injection in the rostral ventromedial medulla of neuropathic rats. / Saadé, Nayef E.; Al Amin, Hassen; Tchachaghian, Sima; Jabbur, Suhayl J.; Atweh, Samir F.

In: Pain, Vol. 149, No. 1, 04.2010, p. 89-99.

Research output: Contribution to journalArticle

Saadé, Nayef E. ; Al Amin, Hassen ; Tchachaghian, Sima ; Jabbur, Suhayl J. ; Atweh, Samir F. / Alteration of GABAergic and glycinergic mechanisms by lidocaine injection in the rostral ventromedial medulla of neuropathic rats. In: Pain. 2010 ; Vol. 149, No. 1. pp. 89-99.
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