Lack of effect by substance P at sites in the substantia gelatinosa where Met-enkephalin reduces the transmission of nociceptive impulses.
In alpha-chloralose anaesthetized spinal cats, Met-enkephalin amide (M-ENKA) and substance P were administered electrophoretically in the substantia gelatinosa while studying the excitation of deeper spinal neurones by noxious and non-noxious cutaneous stimuli. At sites where Met-enkephalin selectively reduced excitation by noxious skin stimuli, substance P was without effect. This result does not support the hypothesis that enkephalins are released at axo-axonic synapses on the terminals of substance P releasing primary afferent fibres.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002415:Cats; D004723:Endorphins / Q000494:pharmacology*; D004745:Enkephalins / Q000494:pharmacology*; D006197:Hair / Q000187:drug effects; D006358:Hot Temperature; D009270:Naloxone / Q000494:pharmacology; D009619:Nociceptors / Q000502:physiology*; D012867:Skin / Q000187:drug effects; D012879:Skin Physiological Phenomena; D013116:Spinal Cord / Q000502:physiology*; D013373:Substance P / Q000494:pharmacology*; D013376:Substantia Gelatinosa / Q000187:drug effects / Q000502:physiology*
D004723:Endorphins; D004745:Enkephalins; D013373:Substance P; D009270:Naloxone