128ROCK ACTIVITY ON THE TEMPERATURE-DEPENDENT RESPONSES OF CALF CARDIAC VEINAt present very little is known about the role of Rho-kinase (ROCK) activity in the effects of temperature on vascular reactivity. To evaluate the role of ROCK activity in the cooling (28 ˚C)- and warming (41˚C)-induced effects on vascular reactivity, isolated calf cardiac vein rings were studied. Rings obtained from calf hearts were suspended in organ baths containing 25 ml of Krebs-Henseleit solution, maintained at 37 ˚C, continuously gassed with 95% O2-5% CO2. At the end of the resting period, the preparations were contracted with carbachol (10-6 M), serotonin (5-HT, 10-6 M), U46619 (10-7 M), PGF2α (10-6 M), or endothelin-1 (ET-1, 10-8 M) at 37˚C in different preparations. The same protocol was repeated at 28 ˚C and 41˚C after the preparations were allowed to equilibrate at this temperature for 60 min. In order to analyze the role of ROCK activity in the cooling- and warming-induced vascular response, each contractile agent was applied in the presence of fasudil (10-6 M) or Y-27632 (10-6 M). Carbachol, 5-HT, U46619, PGF2α and ET-1 produced reproducible contractions. Cooling decreased the contractions to carbachol, 5-HT, U46619, PGF2α and ET-1 and warming enhanced significantly. Treatment with fasudil and Y-27632 at both 28 and 41˚C decreased the responses to carbachol, 5-HT, U46619, PGF2α and ET-1. The results of this study suggests a role for ROCK signalling in the temperature-induced changes of calf cardiac vein.esraatalik@hotmail.comResearch622016Cardiovascular activity,Hypothermia,Rho kinase,HyperthermiaNurullahoğlu-Atalık KEDepartment of Pharmacology, Faculty of Meram Medicine, University of Necmettin Erbakan, Konya, 42080, Turkey