Morphine differentially modulates nociceptive input in the superficial versus the deeper dorsal horn of the medulla (trigeminal nucleus caudalis) in the rat.
Morphine enhanced the noxious thermal stimulus-evoked responses in 4/13 (31%) selectively nocireceptive neurons in the superficial dorsal horn, inhibited the responses in 4/13 (31%) neurons and produced a biphasic effect in 2/13 (17%) neurons. Naloxone antagonized these effects in 7/7 neurons. In contrast, morphine produced a naloxone reversible reduction in the nociceptive responses of 4/4 (100%) multireceptive neurons in the deeper dorsal horn of the medulla. The data are interpreted to indicate that opiates may differentially modulate nociceptive input in the superficial versus the deeper dorsal horn.
Mokha
S S
SS
Department of Physiology, Meharry Medical College, Nashville, TN 37208.
D000818:Animals; D009020:Morphine / Q000494:pharmacology*; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014279:Trigeminal Nucleus, Spinal / Q000187:drug effects*
D009020:Morphine