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Inhibitory effects of stimulation of periaqueductal grey and raphe nucleus magnus on nociceptive responses in cat's spinal dorsal horn neurons

Zhao Zhiqi, Yang Zhenquan, Yang Huanqiao

Shanghai Brain Research Institute, Academia Sinica. Shanghai, China；Shanghai Medical College for Sinica. Shanghai, China

Abstract

1. Inhibitory effects of conditioning stimuli applied to the periaqueductal grey (PAG) and nucleus raphe magnus (NRM) on the nociceptive and non-nociceptive responses of spinal dorsal horn neurones was studied in chloralose-anaesthetized cats. 2. Single dorsal horn neurone was recorded extracellularly in the lumbar spinal cord. According to the pattern of their responses to stimuli, the neurones were classified as non-nociceptive low-threshold, wide dynamic range (WDR), nociceptive heat sensitive and inhibition of spontaneous discharges elicited by stimulation of high-threshold afferents. 3. The majority of dorsal horn neurones tested were markedly inhibited by PAG and NRM stimuli. 4. NRM-induced inhibition was more powerful than PAG-induced one and was antagonized by naloxone (ix.). Nociceptive response was preferentially inhibited by PAG stimulation and both the nociceptive and non-nociceptive response were inhibited by NRM stimulation. 5. The results suggest the involvement of the different neural machnisms in inhibitory effects of PAG and NRM descending on the activity of spinal dorsal horn.

Key words: Periaqueductal grey;Nucleus raphe magnus;Spinal dorsal horn neuron;Inhibition of nociceptive response

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Citing This Article：

Zhao Zhiqi, Yang Zhenquan, Yang Huanqiao. Inhibitory effects of stimulation of periaqueductal grey and raphe nucleus magnus on nociceptive responses in cat's spinal dorsal horn neurons. Acta Physiol Sin 1986; 38 (3): (in Chinese with English abstract).