Spinal R-phenyl-isopropyl adenosine inhibits spinal dorsal horn neurons responding to noxious heat stimulation in the absence and presence of sensitization.
The effects of spinally administered R(-)N6-(2-phenylisopropyl) adenosine (R-PIA) on spinal dorsal horn neurons were investigated in anesthetized rats. Extracellular, single-unit recordings were measured during noxious heating of receptive fields on the hind paw. Three series of experiments were carried out to characterize the effects of R-PIA on spinal dorsal horn neuronal activity. In the first set of experiments, R-PIA dose-dependently suppressed noxiously evoked activity of spinal dorsal horn neurons. In the second set of experiments, R-PIA suppressed noxiously evoked activity in neurons sensitized by the topical application of mustard oil to a region of skin adjacent to their receptive fields. In the third set of experiments, R-PIA prevented mustard oil induced sensitization of dorsal horn neurons. In all cases, the adenosine receptor antagonist theophylline reversed the action of R-PIA. The results of these investigations indicate the involvement of spinal adenosine receptors in spinal pathways of central sensitization and in the modulation of somatically induced noxious pain.
Sumida
T
T
Department of Anesthesiology, Yale University School of Medicine, New Haven, CT 06510, USA.
Smith
M A
MA
Maehara
Y
Y
Collins
J G
JG
Kitahata
L M
LM
D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D006358:Hot Temperature; D008297:Male; D009149:Mustard Plant; D009475:Neurons, Afferent / Q000187:drug effects* / Q000502:physiology; D009619:Nociceptors / Q000187:drug effects* / Q000502:physiology; D017288:Pain Threshold / Q000187:drug effects; D010936:Plant Extracts / Q000494:pharmacology; D010938:Plant Oils; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000166:cytology*; D013806:Theophylline / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*
D010936:Plant Extracts; D010938:Plant Oils; D014665:Vasodilator Agents; C047235:N-(1-methyl-2-phenylethyl)adenosine; D013806:Theophylline; D000241:Adenosine; C027793:mustard oil