Intrathecal [Nphe1]nociceptin( 1-13)NH2 selectively reduces the spinal inhibitory effect of nociceptin.
The effects of intrathecal (i.t.) application of the proposed nociceptin receptor antagonist [Nphe1]nociceptin(1-13)NH2 on the flexor reflex was evaluated in spinalized rats. I.t. [Nphe1]nociceptin (1-13)NH2 dose-dependently facilitated the flexor reflex with no depression. Pretreatment with 16.5 nmol of [Nphe1]nociceptin(1-13)NH2 prevented the development of reflex depression following 0.55 nmol i.t. nociceptin, but strongly enhance the initial excitatory effect of nociceptin. The reflex depressive effect of i.t. endomorphine-2 was not blocked by [Nphe1]nociceptin(1-13)NH2 pretreatment. It is concluded that [Nphe1]nociceptin(1-13)NH2 is a selective antagonist of the spinal receptor mediating the inhibitory action of nociceptin. It can be further suggested that the spinal inhibitory effect of nociceptin may be tonically active.
Xu
Isabella S
IS
Department of Medical Laboratory Sciences and Technology, Karolinska Institutet, Huddinge University Hospital, Sweden.
Grass
Stefan
S
Calo
Girolamo
G
Guerrini
Remo
R
Wiesenfeld-Hallin
Zsuzsanna
Z
Xu
Xiao-Jun
XJ
D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D007278:Injections, Spinal; D009842:Oligopeptides / Q000494:pharmacology; D018847:Opioid Peptides / Q000008:administration & dosage / Q000494:pharmacology*; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex / Q000187:drug effects; D013116:Spinal Cord / Q000187:drug effects* / Q000502:physiology; D000097629:Nociceptin
D000700:Analgesics; D009842:Oligopeptides; D018847:Opioid Peptides; D010446:Peptide Fragments; D000097629:Nociceptin; C403776:nociceptin-(1-13)-NH2, NPhe(1)-; C105294:endomorphin 2