Antinociceptive interactions between intrathecal gabapentin and MK801 or NBQX in rat formalin test.
Antagonists for spinal N-methyl-D-aspartate (NMDA) and amino-hydroxy-methtyl-isoxazolepropionate (AMPA) receptors are effective in attenuating acute nociception or injury-induced hyperalgesia. The antinociception of spinal gabapentin is developed in injury-induced hyperalgesia without affecting acute nociception. The authors evaluated the effects of intrathecal gabapentin, NMDA antagonist (MK801) and AMPA antagonist (NBQX) in the formalin test which shows injury-induced hyperalgesia as well as acute pain. We further assessed the interactions between gabapentin and either MK801 or NBQX. Male Sprague-Dawley rats were implanted with intrathecal catheters. To evoke pain, 50 microL of 5% formalin solution was injected into the hindpaw. The interaction was investigated by a fixed dose analysis or an isobolographic analysis. MK801 and NBQX suppressed flinching responses during phase 1 of the formalin test, while gabapentin had little effect on phase 1. All three agents decreased the phase 2 flinching response. A fixed dose analysis in phase 1 showed that gabapentin potentiated the antinociceptive effect of MK801 and NBQX. Isobolographic analysis in phase 2 revealed a synergistic interaction after coadministration of gabapentin-MK801 or gabapentin-NBQX. Correspondingly, spinal gabapentin with NMDA or AMPA antagonist may be useful in managing acute pain and injury-induced hyperalgesia.
Yoon
Myung Ha
MH
Department of Anesthesiology and Pain Medicine, Chonnam National University, Medical School, Gwangju 501-757, Korea. mhyoon@chonnam.ac.kr
Bae
Hong Beom
HB
Choi
Jeong Il
JI
D000588:Amines / Q000008:administration & dosage / Q000494:pharmacology*; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D003509:Cyclohexanecarboxylic Acids / Q000008:administration & dosage / Q000494:pharmacology*; D016291:Dizocilpine Maleate / Q000494:pharmacology*; D004347:Drug Interactions; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D000077206:Gabapentin; D006930:Hyperalgesia / Q000188:drug therapy; D007278:Injections, Spinal; D008297:Male; D011810:Quinoxalines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000187:drug effects / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000008:administration & dosage / Q000494:pharmacology*
D000588:Amines; D000700:Analgesics; D003509:Cyclohexanecarboxylic Acids; D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin; D016291:Dizocilpine Maleate