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Title: Effect of K<sub>ATP</sub> channel openers on myogenic and neurogenic responses in goat urinary bladder
Authors: Vijayakumar, C
Kathirvel, K
Sardar, K K
Parija, S C
Keywords: Electrical field stimulation
Goat urinary bladder
K<sub>ATP</sub> channels openers
Issue Date: Feb-2007
Publisher: CSIR
Abstract: Isolated goat detrusor muscle exhibited spontaneous contractility with an irregular amplitude and frequency. The spontaneity of detrusor muscle exhibited a mean amplitude as 11.99 ± 0.83 mm and frequency as 1.37 ± 0.16/min. K<sub>ATP</sub>-channel openers namely, cromakalim or pinacidil (10<sup>-7</sup>-10<sup>-4 </sup>M) added cumulatively, elicited a concentration-related inhibition of both amplitude and rate of spontaneous contractions. The mean IC<sub>50 </sub>values for both amplitude and frequency for cromakalim were 3.3 × 10<sup>-6 </sup><i style="">M</i> and 2.9 × 10<sup>-6 </sup><i style="">M</i>, respectively; and for pinacidil were 2.0 × 10<sup>-5 </sup><i style="">M</i> and 1.5 × 10<sup>-5 </sup><i style="">M</i>, respectively. Glibenclamide, a K<sub>ATP</sub>-channel blocker inhibited the cromakalim-induced concentration-related relaxation of spontaneous contractions with a significant increase in its mean IC<sub>50</sub>. ACh -induced concentration-related contractile response was inhibited in the presence of either cromakalim (10<sup>-4 </sup><i style="">M</i>) or pinacidil (10<sup>-4 </sup><i style="">M</i>). The mean EC<sub>50 </sub>value of ACh, in the presence of cromakalim (2.5 × 10<sup>-3 </sup><i style="">M</i>) was significantly increased as compared to the control (1.2 × 10<sup>-6 </sup><i style="">M</i>). In the presence of glibenclamide (10<sup>-5 </sup><i style="">M</i>) the inhibitory effect of cromakalim was significantly reduced with consequent decrease in the EC<sub>50</sub> value (1.9 × 10<sup>-5 </sup><i style="">M</i>). Application of EFS (30 V and 5 ms) on goat urinary bladder strips at 1, 2, 5, 10, 20 and 30 Hz elicited frequency-related contractile responses. Both cromakalim and pinacidil caused a rightward shift in the frequency-related contractile response curve with significant increase in the mean EF<sub>25</sub> and EF<sub>50 </sub>values, respectively. In the presence of glibenclamide (10<sup>-4</sup><i style="">M</i>), the frequency-related inhibitory response curve was shifted to left with significant (P <0.001) increase in the mean EF<sub>25</sub>,<sub> </sub>EF<sub>50</sub> and EF<sub>75. </sub>The present results suggest that in the goat detrusor muscle, agonist and EFS-induced contractile responses were more potently inhibited by cromakalim than pinacidil with activation of glibenclamide sensitive K<sub>ATP </sub>channels.
Description: 185-193
ISSN: 0975-1009 (Online); 0019-5189 (Print)
Appears in Collections:IJEB Vol.45(02) [February 2007]

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