Morphine inhibits antidromic vasodilatation without affecting the excitability of C-polymodal nociceptors in the skin of the rat.
The effect of morphine was examined under identical conditions on (a) antidromic vasodilatation, an 'efferent' function of C-nociceptors in the skin, and (b) afferent responses to heat and pressure of C-polymodal nociceptors. Morphine caused a large, naloxone-reversible, fall in peak antidromic vasodilatation (ADV). However it caused no significant change in heat or mechanical excitability of C-polymodal nociceptors in normal or mildly inflamed skin. The mechanisms by which morphine might affect efferent, but not afferent, functions of C-nociceptors are discussed.
Shakhanbeh
J
J
Department of Physiology, University College London, UK.
Lynn
B
B
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003872:Dermatitis / Q000503:physiopathology; D004558:Electric Stimulation; D008297:Male; D009020:Morphine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009412:Nerve Fibers / Q000187:drug effects*; D009619:Nociceptors / Q000187:drug effects*; D017288:Pain Threshold / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000502:physiology; D012867:Skin / Q000098:blood supply / Q000294:innervation*; D014664:Vasodilation / Q000187:drug effects*
D009270:Naloxone; D009020:Morphine