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Öğe Effects of Cooling on Contractions of Calf Coronary Artery: Role of the Endothelium(2001) Atalık, Kısmet Esra; Şahin, A. S.; Doğan, N.The effects of cooling on vasoconstrictions induced by contractile agents and role of the endothelium in this effect were analyzed in calf coronary artery. Potassium chloride (KCl, 10-3 - 5 × 102 M), 5-hydroxytryptamine (5-HT, 10-9 - 3 × 10-4 M) and carbachol (10-9 - 3 × 10-4 M) induced concentration-dependent contractions at both 37°C and 28°C (cooling). During cooling the sensitivities, but not the maximal responses to KCl, 5-HT and carbachol were significantly lower than at 37°C. Endothelium removal or NG-nitro-L arginine methyl esther (LNAME, 10-5 M) pretreatment did not modify the effect of cooling. These results suggest that cooling-induced responses in calf coronary artery are independent of endothelium (nitric oxide).Öğe Interactions Between Phenylephrine, Clonidine and Xylazine in Rat and Rabbit Aortas(Prous Science, Sa, 2000) Atalık, K. E.; Şahin, A. S.; Doğan, N.The interaction of the a-adrenoceptor agonists clonidine and xylazine with the a-adrenoceptors in the rat and rabbit aortas was investigated. In preparations preconstricted with phenylephrine (10° M), cumulative addition of clonidine and xylazine induced concentration-related vasodilata- tion in the presence of the a-adrenoceptor antagonist yohimbine and the B-blocker propranolol. Neither clonidine nor xylazine treatment inhibited 5-HT- and KCI-induced vasoconstriction. It is concluded that a-agonists have affinity for a-adrenoceptors in rat and rabbit aortas.Öğe Nonadrenergic, Noncholinergic Responses of the Human Colon Smooth Muscle and the Role of K+ Channels in These Responses(PROUS SCIENCE, SA, 2001) Şahin, A. S.; Atalık, K. E.; Günel, E.; Doğan, N.The aim of the present study was to investigate the possible role of notric oxide (NO) as a nonadrenergic, noncholinergic (NANC) mediator in human colon smooth muscle in vitro and to examine its possible interactions with K+ channels. In the presence of atropine (10(-6) M) and guanethidine (10(-5)M).. electrical field stimulation (EFS, 1-10 Hz, 0.3 msec, 50V) for 10 sec induced relaxations which were inhibited by tetrodotoxin (10(-6) M). in the presence of N-G-nitro-L-arginine methyl ester (L-NAME, 10(-4) M), relaxations induced by EFS at 1, 2, 4, 8 and 10 Hz were reduced by 38.7 +/- 4.3, 31.5 +/-3.8, 54.3 +/-5.4, 59.8 +/- 4.5 and 68.6 +/- 5.3% respectively. THe relaxations inhibited by L-NAME were restored by the preincubation of L-argarinine (L-ARG, 10(-3) M) at all frequencies tested. D-Arginine (D-ARG, 10(-3) M) had no effect. Tetraethylammonium (TEA, 10(-4) M) or glibenclamidine (10(-6) M) significantly decreased the relaxations induced induced by EFS. Exogenously applied sodium nitroprusside caused concentration-dependent relaxation with prusside. In conclusion, our data indicate that NO is involved in NANC nerve-mediated relaxation in the human calcium-dependent and ATP-sensitive K+ channels.Öğe Nonadrenergic, Noncholinergic Responses of the Rabbit Detrusor Smooth Muscle and the Role of L-Arginine/Nitric Oxide Pathway in These Responses(Prous Science, Sa, 2000) Şahin, A. S.; Atalık, K. E.; Doğan, N.In the present study, nonadrenergic, noncholinergic (NANC) responses of rabbit detrusor smooth muscle and the possible involvement of the L-arginine/nitric oxide (L-ARG/NO) pathway was investigated. In the presence of atropine (10(-6) M) and guanithidine (10(-5) M), frequency-response curves were obtained by stimulating tissue with 10-sec trains or increasing frequencies (1-10 Hz) with 3-min intervals between stimulations. Electrical field stimulation (EFS) evoked a biphasic response in rabbit detrusor smooth muscle, consisting of an initial contraction followed by relaxation. ATP desensitization significantly inhibited contractions. L-NAME(10(-5) M) increased the contractions by a maximum of 33 +/- 5% at 1 Hz, 37 +/- 5% at 2 Hz, 18 +/- 4% at 4 Hz. 20 +/- 3% at 8 Hz and 15 +/- 4% at 10 Hz. In detrusor preparations, exposure to L-NAME (N-G-nitro-L-arginine methyl ester, 10(-5) M) significantly reduced the maximal relaxation to electrical stimulation to 7 +/- 3% of the control. In the presence of L-ARG (10(-4) M), contractions induced by electrical field stimulation (EFS) at 1, 2, 4, 8 and 10 Hz were reduced by 20 +/- 4, 24 +/- 3, 25 +/- 3, 20 +/- 3 and 30 +/- 5%, respectively. Exposure to L-ARG (10(-4) M) significantly increased the maximal relaxation to electrical stimulation to 52 +/- 5% of the control. Exogenously applied ATP (10(-5)- 10(-2) M) to rabbit detrusor muscle resulted in contractions while sodium nitroprusside (10(-7)-10(-3) M) caused concentration-dependent relaxation. These results suggest that nitric oxide (NO) acts as an inhibitory NANC neurotransmitter in the rabbit detrusor smooth muscle. Additionally, NANC contractions mediated by ATP released from NANC nerves, may be masked by thr L-ARG/NO pathway in this tissue.
