Effects of stimulation of superior colliculus on nociceptive unit discharges in parafascicular neurons and nocifensive reflex of hind limb in rat.
Effects of stimulation of the superior colliculus (SC) on the spontaneous and nociceptive discharges of parafascicular (PF) neurons were investigated in 43 urethane-anesthetized rats. Two groups of PF cells were sampled according to their responses to noxious stimuli: 59 of them were 'nociceptive-on' and 12 'nociceptive-off'. Following stimulation of the intermediate and deep layers of SC, the firing rate of nociceptive discharge of 'nociceptive-on' cells was inhibited significantly (-76 +/- 5%, P less than 0.01) in 75% cases tested, while the nociceptive response of 'nociceptive-off' cells was disinhibited markedly (79 +/- 9%, P less than 0.01) in 67% cases by the same stimulation. In 30 animals of this series the latency of hind limb withdrawal reflex elicited by noxious skin heating was compared before and after SC stimulation. In 24 cases in which the stimulating electrodes were positioned exactly in intermediate-deep layers of SC, SC stimulation lengthened the latency by 62 +/- 8% (P less than 0.01), while in 6 cases in which the electrodes drifted from these areas, the latency was not changed following the same stimulation.
Zhang
Z H
ZH
Department of Neurobiology, Shanxi Medical College, People's Republic of China.
Xie
Y F
YF
Qiao
J T
JT
D000818:Animals; D004558:Electric Stimulation; D005260:Female; D006614:Hindlimb / Q000294:innervation / Q000502:physiology*; D008297:Male; D009474:Neurons / Q000502:physiology*; D009619:Nociceptors / Q000502:physiology*; D051381:Rats; D011930:Reaction Time; D012018:Reflex / Q000502:physiology*; D013477:Superior Colliculi / Q000166:cytology / Q000502:physiology*