Effects of microinjection of kainic acid into nucleus raphe dorsalis on electr()-acupuncture, morphine and stress analgesia

The purpose of this investigation was to observe the changes of electro-acupunc-ture, morphine and stress analgesia in the same rat after microinjection of kainic acid (KA) 0.75 Ul/0.75 Ug into nucleus rapne dorsalis (DR). The morphological structure, fluorescence histochemistry, neurobiochemistry were associated with the behavior of rats to clarify the role of the serotonergic neurons in DR on 3 different analgesia. After the microinjection the rats became violen t and restless. There was a significant reduction in the contents of 5-HT and 5-HIAA in telencephalon and diencephalon. A marked loss of neuronal perikarya together with gliosis was seen in the injected area of DR. The fluorescerice of 5-HT-containing cells in DR significantly decreased. No marked change in the baseline pain thresholdo was observed. But the electro-acupuncture and stress analgesia were significantly diminished while the morphine analgesia was not. These results show that l) The serotonergic neurons in DR can be damaged by KA; 2) The serotonergic neurons in DR play an important role in electro-acupuncture and stress analgesia. The morphine analgesia has no close relationship with serotonergic neurons in DR.