Cerebellar stimulation modulates thalamic noxious-evoked responses.
Parafascicular (PF) neurons responding to noxious stimuli and focal electrical stimulation of midbrain, diencephalon, and hypothalamic nuclei, which send projections to PF, modulates the PF spontaneous and noxious-evoked responses. Some cerebellar efferents ascend to PF. This investigation attempted to study the effect of cerebellar stimulation on spontaneous and noxious-evoked PF neuronal activity in rats. It was observed that 26% (73/280) of PF neurons responded to a noxious stimulus. The PF neuronal population exhibits two cell types according to their response pattern following the noxious stimulus. One type of PF neurons were excited (n = 53) and were classified as nociceptive-on cells. The second type of PF neurons responded to noxious stimulus by a decrease in the ongoing firing rate (n = 20) and were classified as nociceptive-off cells. The responses of these two types of nociceptively identified cells were tested following cerebellar lateral nucleus stimulation (Lat.N.S.) utilizing several current intensities. Lat.N.S. with lower intensities (0.1-0.2 mA) elicited suppression of both spontaneous and nociceptive-evoked discharges of the nociceptive-on neurons, although higher intensities (0.4-0.6 mA) elicited excitation on both discharges of this type of neuron. In contrast, Lat.N.S. induced a monophasic intensity-dependent suppression of both the spontaneous and the nociceptive-evoked discharges of the nociceptive-off neurons. The results indicate that Lat.N.S. modulates the nociceptive-evoked responses of PF neurons. The possible role and related pathways of cerebellum in modulating noxious input were discussed.
Liu
F Y
FY
Department of Neurobiology, Shanxi Medical College, Taiyuan, P.R., China.
Qiao
J T
JT
Dafny
N
N
D000818:Animals; D002529:Cerebellar Nuclei / Q000502:physiology*; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006651:Histocytochemistry; D008297:Male; D008839:Microelectrodes; D009474:Neurons / Q000502:physiology; D009619:Nociceptors / Q000502:physiology; D010146:Pain / Q000503:physiopathology; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000502:physiology; D013788:Thalamus / Q000502:physiology*