Activity-induced plasticity in brain stem pain modulatory circuitry after inflammation.
Brain stem descending pathways modulate spinal nociceptive transmission. In a lightly anesthetized rat preparation, we present evidence that such descending modulation undergoes time-dependent changes following persistent hindpaw inflammation. There was an initial decrease and a subsequent increase in the excitability of neurons in the rostral ventromedial medulla (RVM) involving facilitation and inhibition. These changes were most robust after stimulation of the inflamed paw although similar findings were seen on the non-inflamed paw and tail. The enhanced descending modulation appeared to be mediated by changes in the activation of the NMDA excitatory amino acid receptor. These findings demonstrate the dynamic plasticity of the pain modulating pathways in response to persistent tissue injury.
Terayama
R
R
Department of Oral and Craniofacial Biological Sciences, Dental School, University of Maryland, Baltimore 21201-1586, USA.
Guan
Y
Y
Dubner
R
R
Ren
K
K
D000818:Animals; D001522:Behavior, Animal; D004525:Efferent Pathways / Q000503:physiopathology; D004558:Electric Stimulation; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D006358:Hot Temperature; D007249:Inflammation / Q000503:physiopathology*; D008297:Male; D008526:Medulla Oblongata / Q000503:physiopathology*; D016202:N-Methylaspartate / Q000494:pharmacology; D009433:Neural Inhibition; D009473:Neuronal Plasticity; D009619:Nociceptors / Q000503:physiopathology; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time; D017470:Receptors, Glutamate / Q000502:physiology; D013268:Stimulation, Chemical; D009435:Synaptic Transmission / Q000187:drug effects
D018690:Excitatory Amino Acid Agonists; D017470:Receptors, Glutamate; D016202:N-Methylaspartate