Dynorphin A (1-13) potentiates dynorphin A (1-17) on loss of the tail-flick reflex after intrathecal injection in the rat.
Dynorphin A (1-13) or dynorphin A (1-17) administered intrathecally to rats induces a dose-dependent loss of the tail-flick reflex and a reversible hindlimb paralysis. Although their potency is comparable, dynorphin A (1-17) is less efficacious in producing loss of the tail-flick reflex. These data suggest that dynorphin A (1-17) acts as a partial agonist or exerts its neurotoxic effect in the presence of an endogenous non-competitive inhibitor. To determine whether these substances act at similar sites we performed isobolographic analysis. This analysis revealed that dose-additivity exists for paralysis whereas deviation from dose-additivity exists for loss of the tail-flick reflex.
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Department of Pharmacology, University of Illinois College of Medicine, Chicago 60612.
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D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004399:Dynorphins / Q000008:administration & dosage / Q000494:pharmacology*; D007278:Injections, Spinal; D008297:Male; D010147:Pain Measurement / Q000187:drug effects; D010243:Paralysis / Q000139:chemically induced; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology*; D004856:Postural Balance / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects
D000700:Analgesics; D010446:Peptide Fragments; C026843:dynorphin (1-13); D004399:Dynorphins