Activation of a bulbospinal opioidergic projection by pain stimuli in the awake rat.
We examined the expression of preproenkephalin mRNA in pain-modulating regions of the rat's brainstem using in situ hybridization histochemistry. We found that neurones in the Kölliker-Fuse nucleus, which receives projections from spinal nociceptive-specific cells, express enkephalin mRNA, that this expression is increased by noxious pinch applied to the skin of awake animals, and that these enkephalinergic neurones are part of a descending system that terminates in the rostroventral medulla and the spinal cord. These findings show that natural noxious stimuli activate opioidergic bulbospinal neurones that could directly modulate spinal nociceptive transmission.
Blomqvist
A
A
Department of Cell Biology, Faculty of Health Sciences, University of Linköping, Sweden.
Hermanson
O
O
Ericson
H
H
Larhammar
D
D
D000818:Animals; D004558:Electric Stimulation; D004745:Enkephalins / Q000235:genetics*; D017403:In Situ Hybridization; D008297:Male; D008526:Medulla Oblongata / Q000378:metabolism / Q000503:physiopathology*; D009434:Neural Pathways / Q000502:physiology; D010146:Pain / Q000503:physiopathology*; D011498:Protein Precursors / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000378:metabolism / Q000503:physiopathology*
D004745:Enkephalins; D011498:Protein Precursors; D012333:RNA, Messenger; C033660:preproenkephalin