title: A possible correlation between oxytocin-induced and angiotensin IV-induced anti-hyperalgesia at the spinal level in rats.
abstract: In our previous study, we showed that intrathecal (i.t.) administration of angiotensin IV (Ang IV), an insulin-regulated aminopeptidase (IRAP) inhibitor, attenuated inflammatory hyperalgesia in rats. Using the plantar test in rats with carrageenan-induced paw inflammation, we investigated the possible mechanism(s) of this effect. Because i.t. oxytocin was reported to produce a dose-dependent anti-hyperalgesia in rats with inflammation, we speculate that there is a possible correlation between oxytocin-induced and Ang IV-induced anti-hyperalgesia. Using i.t. co-administered atosiban (oxytocin receptor antagonist), the anti-hyperalgesia by Ang IV was completely abolished. This indicated that oxytocin could be the major IRAP substrate responsible for the anti-hyperalgesia by Ang IV. When Ang IV was co-administered with a low dose of oxytocin, there was a significant enhancing effect of Ang IV on oxytocin-induced anti-hyperalgesia. In recent reports, electrical stimulation on the paraventricular hypothalamic nucleus (PVN) was proved to increase oxytocin release at the spinal cord. Our results also showed that Ang IV could prolong the anti-hyperalgesia induced by PVN stimulation. This suggests a possible protective effect of Ang IV on endogenous oxytocin degradation/dysfunctioning. Moreover, we examined the local effect of intraplantarly injected Ang IV in the same model. Our results showed no effect of local Ang IV on hyperalgesia and paw edema, indicating that Ang IV may not regulate the peripheral inflammatory process. Overall, our study suggests that Ang IV may act through the inhibition of the activity of IRAP to reduce the degradation of oxytocin at the spinal cord, thereby leading to anti-hyperalgesia in rats with inflammation.
authors.affiliation: Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Lok-Hi
authors.initials: LH
authors.lastname: Chow
authors.forename: Pao-Luh
authors.initials: PL
authors.lastname: Tao
authors.forename: Jin-Chung
authors.initials: JC
authors.lastname: Chen
authors.forename: Ruey-Ming
authors.initials: RM
authors.lastname: Liao
authors.forename: En-Pei
authors.initials: EP
authors.lastname: Chang
authors.forename: Eagle Yi-Kung
authors.initials: EY
authors.lastname: Huang
mesh_terms: D000804:Angiotensin II / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000502:physiology; D000818:Animals; D002351:Carrageenan; D010122:Cystinyl Aminopeptidase / Q000378:metabolism; D004487:Edema / Q000139:chemically induced / Q000503:physiopathology; D004558:Electric Stimulation; D005528:Foot / Q000473:pathology; D006930:Hyperalgesia / Q000139:chemically induced / Q000503:physiopathology*; D007278:Injections, Spinal; D008297:Male; D010121:Oxytocin / Q000494:pharmacology / Q000502:physiology*; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018045:Receptors, Oxytocin / Q000037:antagonists & inhibitors / Q000378:metabolism; D013116:Spinal Cord / Q000187:drug effects / Q000503:physiopathology; D014668:Vasotocin / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D018045:Receptors, Oxytocin; C047046:atosiban; D000804:Angiotensin II; C012877:angiotensin II, des-Asp(1)-des-Arg(2)-Ile(5)-; D010121:Oxytocin; D002351:Carrageenan; D010122:Cystinyl Aminopeptidase; C105964:leucyl-cystinyl aminopeptidase; D014668:Vasotocin