Nociceptive responses in nucleus parafascicularis thalami are modulated by dorsal raphe stimulation and microiontophoretic application of morphine and serotonin.
Single-cell experiments were undertaken to examine the hypothesis that serotonin (5-HT) and morphine participate in ascending pain suppression phenomena. The observations demonstrate that: 1) dorsal raphe stimulation (DRS) modulates the spontaneous activity and the noxious-evoked responses of parafasciculus (PF) neurons, and the modulating effects of DRS are altered by either naloxone or methysergide; 2) morphine ejection into the PF alters the spontaneous activity and the noxious-evoked responses of PF neurons, and naloxone prevents morphine effects; and 3) serotonin ejection into the PF alters the spontaneous activity and the noxious-evoked responses of PF neurons and methysergide prevents the serotonin effects. These findings support the hypothesis that opioid and serotonin participate, at least in part, in the control of ascending pain mechanisms.
Reyes-Vazquez
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C
Department of Neurobiology and Anatomy, University of Texas Medical School, Houston 77025.
Qiao
J T
JT
Dafny
N
N
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D011903:Raphe Nuclei / Q000378:metabolism / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000494:pharmacology*; D013787:Thalamic Nuclei / Q000187:drug effects / Q000503:physiopathology*
D012701:Serotonin; D009270:Naloxone; D009020:Morphine; D008784:Methysergide