Neurochemical changes after morphine, dizocilpine or riluzole in the ventral posterolateral thalamic nuclei of rats with hyperalgesia.
A number of studies suggest the involvement of glutamate in central hyperalgesia through NMDA receptors in animal models of inflammation. Most studies analyze glutamate effects at the spinal cord level. In this work, the effects of morphine, dizocilpine and riluzole on the hyperalgesia induced by carrageenan administration in the rat paw model were investigated. The effects of morphine and riluzole on the release of glutamate and aspartate and on the concentrations of citrulline and arginine in dialysates of the ventral posterolateral nucleus of the thalamus were also examined. All three drugs decreased hyperalgesia when administered prior to carrageenan injection. Morphine decreased the glutamate concentration in dialysates of the ventral posterolateral nucleus but did not affect the concentrations of the other amino acids. The effect of morphine was observed in the absence of painful stimulation and when pressure applied to the rat paw induced a nociceptive reaction. Riluzole decreased the concentrations of glutamate and aspartate and those of citrulline and arginine in the presence or absence of painful stimulation. These experiments suggest that morphine and riluzole attenuate the hyperalgesia induced by injection of carrageenan in the rat hind paw, at least partly, by decreasing glutamate release in the ventral posterolateral thalamic nucleus.
Abarca
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Department of Pharmacology, Faculty of Biological Sciences, Casilla 160-C, Concepción University, Concepcion, Chile.
Silva
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E
Sepúlveda
M J
MJ
Oliva
P
P
Contreras
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E
D000704:Analysis of Variance; D000818:Animals; D001120:Arginine / Q000187:drug effects / Q000378:metabolism; D001224:Aspartic Acid / Q000187:drug effects / Q000378:metabolism; D002351:Carrageenan / Q000009:adverse effects; D002956:Citrulline / Q000187:drug effects / Q000378:metabolism; D015314:Dialysis Solutions / Q000737:chemistry; D016291:Dizocilpine Maleate / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D018698:Glutamic Acid / Q000187:drug effects / Q000378:metabolism; D006614:Hindlimb; D006930:Hyperalgesia / Q000139:chemically induced / Q000517:prevention & control*; D008297:Male; D017551:Microdialysis; D009020:Morphine / Q000494:pharmacology*; D018696:Neuroprotective Agents / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D019782:Riluzole / Q000494:pharmacology*; D013787:Thalamic Nuclei / Q000737:chemistry / Q000187:drug effects*
D015314:Dialysis Solutions; D018696:Neuroprotective Agents; D002956:Citrulline; D001224:Aspartic Acid; D018698:Glutamic Acid; D016291:Dizocilpine Maleate; D009020:Morphine; D019782:Riluzole; D002351:Carrageenan; D001120:Arginine