Effects of K^+ Channel Modulators on Oscillatory Contractions in Sinoaortic Denervated Rat Aortas(Pharmacology)

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Sinoaortic denervated (SAD) rats present arterial pressure lability without sustained hypertension. We investigated the relation between sinoaortic denervation and the occurrence of oscillatory contractions in SAD rat aortas, as well as the effect of various K^+ channel modulators on these oscillations. Aortas were removed and concentration-effect curves to phenylephrine (0.01 to 10μM) were constructed in arteries from SAD and Sham-operated rats in order to verify the occurrence of oscillations. We also evaluated the effects of various K^+ channel modulators on these oscillations. Only SAD rat aortas exhibited oscillatory contractions. Tetraethylammonium increased the frequency (28.5±3.5 to 41.5±4.5 counts/5 min) and amplitude (0.435±0.07 to 0.630±0.09g) of the oscillations. Apamin and 4-aminopyridine did not alter the oscillations. Barium chloride converted the oscillatory contractions to a tonic contraction. Pinacidil rapidly blocked the oscillatory contractions and glibenclamide evoked reduction in amplitude from 0.410±0.07 to 0.180±0.06g. Iberiotoxin increased the frequency of oscillatory contractions (from 28.0±3.5 to 51.5±7.5 counts/5 min) but decreased the amplitude (from 0.410±0.08 to 0.195±0.2g). Our results demonstrate that SAD rat aortas exhibit oscillatory contractions and K^+ channels, mainly K_<ATP> and BK_<Ca>, play a dominant role in these oscillations.
2007-11-01