title: Dual effects of Rho-kinase inhibitors on a rat model of inflammatory pain.
abstract: BACKGROUND
  Rho-kinases (ROCKs), a family of small GTP-dependent enzymes, are involved in a range of pain models, and their inhibition typically leads to antinociceptive effects.
  
  
  OBJECTIVE
  To study the effects of inhibiting ROCKs using two known inhibitors, Y27632 and HA1077 (fasudil), administered locally, on nociception and paw edema in rats.
  
  
  METHODS
  A range of doses of Y27632 or HA1077 (2.5 μg to 1000 μg) were injected locally into rat paws alone or in combination with carrageenan, a known proinflammatory stimulus. Nociceptive responses to mechanical stimuli and increased paw volume, reflecting edema formation, were measured at 2 h and 3 h, using a Randall-Selitto apparatus and a hydroplethysmometer, respectively.
  
  
  RESULTS
  Animals treated with either ROCK inhibitor showed biphasic nociceptive effects, with lower doses being associated with pronociceptive, and higher doses with antinociceptive responses. In contrast, a monophasic dose-dependent increase in edema was observed in the same animals. Local injection of 8-bromo-cyclic (c)GMP, an activator of the nitric oxide⁄cGMP⁄protein kinase G pathway, also produced biphasic effects on nociceptive responses in rat paws; however, low doses were antinociceptive and high doses were pronociceptive. Local administration of cytochalasin B, an inhibitor of actin polymerization and a downstream mediator of ROCK activity, reversed the antinociceptive effect of Y27632.
  
  
  CONCLUSIONS
  The results of the present study suggest that ROCKs participate in the local mechanisms associated with nociception⁄antinociception and inflammation, with a possible involvement of the nitric oxide⁄cGMP⁄protein kinase G pathway. Also, drug effects following local administration may differ markedly from the effects following systemic administration. Finally, separate treatment of pain and edema may be needed to maximize clinical benefit in inflammatory pain.
authors.forename: Patricia
authors.initials: P
authors.lastname: Paiva-Lima
authors.forename: Y S
authors.initials: YS
authors.lastname: Bakhle
authors.forename: Janetti Nogueira
authors.initials: JN
authors.lastname: Francischi
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000577:Amides / Q000494:pharmacology*; D000818:Animals; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007249:Inflammation; D008297:Male; D059225:Nociception / Q000187:drug effects*; D059226:Nociceptive Pain / Q000201:enzymology*; D017288:Pain Threshold / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors*
chemical_list: D000577:Amides; D004791:Enzyme Inhibitors; D011725:Pyridines; C108830:Y 27632; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D054460:rho-Associated Kinases; C049347:fasudil