Failure of ES 52, a highly potent enkephalinase inhibitor, to affect nociceptive transmission by rat dorsal horn convergent neurones.
The effects of ES 52, a highly potent derivative of the enkephalinase (enkephalin-dipeptidylcarboxypeptidase) inhibitor thiorphan, were studied on nociceptive activities of dorsal horn convergent neurones in the anaesthetized rat. Neither the C-fibre component of the responses elicited by supramaximal electrical stimulation of the hindpaw excitatory receptive fields nor diffuse noxious inhibitory controls triggered by immersion of the tail in 46-48 degrees C waterbaths, were affected by ES 52. Thus we conclude that, in our experimental conditions, modulations of the transmission of nociceptive messages at the spinal level are not greatly modified by specifically blocking the degradation of enkephalins. If a major role for enkephalinase (vs aminopeptidase) in the catabolism of enkephalins at the spinal level can be confirmed, then comparison of the present data with our previous results obtained using the opioid antagonist naloxone, might suggest a predominant role for proenkephalin B products (i.e. dynorphins and/or alpha-neo-endorphin) in modulating nociceptive transmission in the spinal cord.
Villanueva
L
L
Cadden
S
S
Chitour
D
D
Le Bars
D
D
D000603:Amino Acids, Sulfur / Q000494:pharmacology*; D000818:Animals; D004745:Enkephalins / Q000502:physiology*; D008297:Male; D009619:Nociceptors / Q000187:drug effects*; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D013116:Spinal Cord / Q000187:drug effects / Q000503:physiopathology*; D009435:Synaptic Transmission / Q000187:drug effects; D015244:Thiorphan / Q000031:analogs & derivatives*; D008625:Tiopronin / Q000031:analogs & derivatives / Q000494:pharmacology*
D000603:Amino Acids, Sulfur; D004745:Enkephalins; C040246:ES 52; D015244:Thiorphan; D008625:Tiopronin