The Effect Of Morphine On Spinal Dorsal Horn Projection Neurons In Rats

Part IRole of Spinal GABAergic and Glycinergic Tone in the Effect of Morphine on Deep Dorsal Horn Projection Neurons in Neuropathic Pain RatObjective To study the inhibitory effect of spinal topical morphine on the dorsal horn projection neurons in nerve-injured rat; To explore the role of GABAergic and glycinergic tone in the inhibitory effect of morphine on deep dorsal horn projection neurons in nerve-injured rat. Methods Single-unit activity of dorsal horn projection neurons was recorded in anesthetized L₅/L₆ nerve-ligated rats. Allodynia was determined by behavior test in sham and nerve-injured rats. Thirty-three SD rats were allocated into four groups. Mu receptor antagonist group (group A, n = 7), the evoked firing activity was recorded as control after 5 min of baseline recording. The effect of spinal topical application of 10 μM morphine was tested 10 min after each of the four repeated doses of morphine. Before the forth morphine, 1 μM of specific μ receptor antagonist CTAP was applied spinally. In normal control group (groupC, n = 10), sham operation control group (group S, n = 6) and nerve-injured group (group I, n = 10), the evoked firing activity was recorded as control after 5 min of baseline recording. The evoked...