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IJEB Vol.45(02) [February 2007] >


Title: Effect of KATP 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
KATP 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. KATP-channel openers namely, cromakalim or pinacidil (10-7-10-4 M) added cumulatively, elicited a concentration-related inhibition of both amplitude and rate of spontaneous contractions. The mean IC50 values for both amplitude and frequency for cromakalim were 3.3 × 10-6 M and 2.9 × 10-6 M, respectively; and for pinacidil were 2.0 × 10-5 M and 1.5 × 10-5 M, respectively. Glibenclamide, a KATP-channel blocker inhibited the cromakalim-induced concentration-related relaxation of spontaneous contractions with a significant increase in its mean IC50. ACh -induced concentration-related contractile response was inhibited in the presence of either cromakalim (10-4 M) or pinacidil (10-4 M). The mean EC50 value of ACh, in the presence of cromakalim (2.5 × 10-3 M) was significantly increased as compared to the control (1.2 × 10-6 M). In the presence of glibenclamide (10-5 M) the inhibitory effect of cromakalim was significantly reduced with consequent decrease in the EC50 value (1.9 × 10-5 M). 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 EF25 and EF50 values, respectively. In the presence of glibenclamide (10-4M), the frequency-related inhibitory response curve was shifted to left with significant (P <0.001) increase in the mean EF25, EF50 and EF75. 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 KATP channels.
Page(s): 185-193
ISSN: 0975-1009 (Online); 0019-5189 (Print)
Source:IJEB Vol.45(02) [February 2007]

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