Differential actions of spinal analgesics on mono-versus polysynaptic Adelta-fibre-evoked field potentials in superficial spinal dorsal horn in vitro.
Processing of nociceptive information can be modulated at various levels in spinal cord that may range from changes of neurotransmitter release from primary afferent Adelta- or C-fibres to excitability changes of spinal interneurones or motoneurones. The site and mechanism of action of spinal analgesics has been assessed with a number of in vivo and in vitro methods with sometimes conflicting results. Here, we have used transverse spinal cord slices with attached dorsal roots to simultaneously record mono- and polysynaptic Adelta-fibre-evoked field potentials in superficial spinal dorsal horn. Two classical spinal analgesics, morphine and clonidine, and the metabotropic glutamate receptor agonist (IS,3R)-1-aminocyclopentane-1,3-dicarboxylic acid ((1S,3R)-ACPD) differentially affected mono- and polysynaptic Adelta-fibre-evoked transmission in spinal dorsal horn. Polysynaptic responses were dose-dependently inhibited while the monosynaptic response remained unaffected. These results suggest that spinal analgesics may preferentially affect polysynaptic but not monosynaptic Adelta-fibre-evoked responses in superficial spinal dorsal horn.
Ruscheweyh
Ruth
R
Institute of Physiology and Pathophysiology, Heidelberg University, Im Neuenheimer Feld 326, 69120 Heidelberg, Germany.
Sandkühler
Jürgen
J
D000200:Action Potentials / Q000187:drug effects; D000700:Analgesics / Q000008:administration & dosage* / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D003515:Cycloleucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007278:Injections, Spinal; D009020:Morphine / Q000494:pharmacology; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists; D017981:Receptors, Neurotransmitter / Q000037:antagonists & inhibitors; D013116:Spinal Cord / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects*
D000700:Analgesics; D000701:Analgesics, Opioid; D018094:Receptors, Metabotropic Glutamate; D017981:Receptors, Neurotransmitter; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; D009020:Morphine; D003000:Clonidine