Antinociceptive effects of morphine injected into the nucleus parafascicularis thalami of the rat.
The antinociceptive action of morphine microinjected into the nucleus parafascicularis thalami (nPf) on pain behaviors organized at different levels of the neuraxis was examined in the rat. Behaviors organized at spinal (spinal motor reflexes, SMRs), medullary (vocalizations during shock, VDSs), and forebrain (vocalization afterdischarges, VADs) levels were elicited by noxious tailshock. Morphine administered into nPf generated dose-dependent increases in thresholds of VDS and VAD, but failed to elevate SMR thresholds. Increases in vocalization thresholds were reversed in a dose-dependent manner by the microinjection of the mu-opiate receptor antagonist, methylnaloxonium, into nPf. Results are discussed in terms of the relative influence of nPf-administered morphine on nociceptive processing at spinal versus supraspinal levels of the neuraxis.
Harte
S E
SE
Department of Psychology, Wayne State University, 71 W. Warren Avenue, Detroit, MI 48202, USA.
Lagman
A L
AL
Borszcz
G S
GS
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D004056:Differential Threshold / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004597:Electroshock; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology; D008845:Microinjections; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009619:Nociceptors / Q000187:drug effects*; D016548:Prosencephalon / Q000502:physiology; D000644:Quaternary Ammonium Compounds; D051381:Rats; D020318:Rats, Long-Evans; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors; D013116:Spinal Cord / Q000502:physiology; D013787:Thalamic Nuclei / Q000187:drug effects / Q000502:physiology*; D014828:Vocalization, Animal / Q000187:drug effects / Q000502:physiology
D000701:Analgesics, Opioid; D000644:Quaternary Ammonium Compounds; D017450:Receptors, Opioid, mu; D009270:Naloxone; C041269:N-methylnaloxone; D009020:Morphine