Morphine-induced Modulation of Nociceptive Spinal Dorsal Horn Neuronal Activities after Formalin-induced Inflammatory Pain

• 영문명: Morphine-induced Modulation of Nociceptive Spinal Dorsal Horn Neuronal Activities after Formalin-induced Inflammatory Pain
• 발행기관: 대한생리학회-대한약리학회
• 저자명: Joo Min Park Kang Wu Li Sung Jun Jung Jun Kim Sang Jeong Kim
• 간행물 정보: 『The Korean Journal of Physiology & Pharmacology』제9권 제2호, 77~86쪽, 전체 10쪽
• 주제분류: 의약학 > 의학일반
• 파일형태: PDF
• 발행일자: 2005.01.01

영문 초록

In this study, we examined the morphine-induced modulation of the nociceptive spinal dorsal horn neuronal activities before and after formalin-induced inflammatory pain. Intradermal injection of formalin induced time-dependent changes in the spontaneous activity of nociceptive dorsal horn neurons. In naïve cats before the injection of formalin, iontophoretically applied morphine attenuated the naturally and electrically evoked neuronal responses of dorsal horn neurons. However, neuronal responses after the formalin-induced inflammation were significantly increased by morphine. Bicuculline, GABA_A antagonist, increased the naturally and electrically evoked neuronal responses of dorsal horn neurons. This increase in neuronal responses due to bicuculline after the formalin-induced inflammation was larger than that in the naïve state, suggesting that basal GABA_A tone increased after the formalin injection. Muscimol, GABA_A agonist, reduced the neuronal responses before the treatment with formalin, but not after formalin treatment, again indicating an increase in the GABAergic basal tone after the formalin injection which saturated the neuronal responses to GABA agonist. Morphine-induced increase in the spinal nociceptive responses after formalin treatment was inhibited by co-application of muscimol. These data suggest that formalin-induced inflammation increases GABA_A basal tone and the inhibition of this augmented GABA_A basal tone by morphine results in a paradoxical morphine- induced increase in the spinal nociceptive neuronal responses after the formalin-induced inflammation.

키워드

Nociceptive dorsal horn neurons Morphine spinal cord GABA_A basal tone Subacute inflammatory state