title: Differentiation between Aδ and C fibre evoked nociceptive reflexes by TTX resistance and opioid sensitivity in the cat.
abstract: The contribution of nociceptive Aδ-fibres and C-fibres of the central pad of the foot to nociceptive spinal flexor reflex pathways (FRA-type) and to nociceptive excitatory reflex pathways to foot extensors (non-FRA type) was investigated in high spinal cats. Persisting effects after complete blocking of A-fibres by tetrodotoxin (TTX) application were thus attributed to nociceptive C-fibres. The results revealed that both Aδ and C-fibre afferents contributed to nociceptive reflexes of a FRA-pattern and of a non-FRA pattern. Thereby, the effects of Aδ-fibres were evoked with a distinctly shorter delay than those of C-fibres. Furthermore, Aδ-fibres partly exerted a significant inhibitory influence on the C-fibre action in FRA and non-FRA pathways. Treatment with different opioid receptor agonists (DAMGO and DSLET) and subsequently with naloxone revealed that a distinct part of the opioid action on nociceptive reflex pathways of the FRA-type and of the non-FRA type was evidently exerted via Aδ-fibres.
authors.affiliation: Institute of Physiology, Georg August University of Göttingen, Waldweg 33, D-37073 Göttingen, Germany. eschomb@gwdg.de
authors.forename: Eike D
authors.initials: ED
authors.lastname: Schomburg
authors.forename: Payam
authors.initials: P
authors.lastname: Dibaj
authors.forename: Heinz
authors.initials: H
authors.lastname: Steffens
mesh_terms: D000700:Analgesics / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D002415:Cats; D004305:Dose-Response Relationship, Drug; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D005260:Female; D005528:Foot / Q000294:innervation; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009413:Nerve Fibers, Myelinated / Q000187:drug effects* / Q000502:physiology; D036421:Nerve Fibers, Unmyelinated / Q000187:drug effects* / Q000502:physiology; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D012018:Reflex / Q000187:drug effects*; D013116:Spinal Cord / Q000166:cytology*; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D000700:Analgesics; D000701:Analgesics, Opioid; D000779:Anesthetics, Local; D009292:Narcotic Antagonists; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009270:Naloxone; D013779:Tetrodotoxin; D004743:Enkephalin, Leucine; C034318:enkephalin, Ser(2), Leu(5), Thr(6)-