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Effects of intrathecal injection of a hyperpolarization‐activated channel (I h ) inhibitor ZD7288 on bladder function in urethane‐anesthetized rats
Author(s) -
Masuda Noriyuki,
Masuda Hitoshi,
Matsuyoshi Hiroko,
Chancellor Michael B.,
de Groat William C.,
Yoshimura Naoki
Publication year - 2008
Publication title -
neurourology and urodynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 90
eISSN - 1520-6777
pISSN - 0733-2467
DOI - 10.1002/nau.20563
Subject(s) - cystometry , medicine , urination , isovolumetric contraction , spinal cord , anesthesia , decerebration , hcn channel , urinary bladder , reflex , urology , blood pressure , urinary system , diastole , receptor , ion channel , psychiatry
Aims The role of I h channels at the spinal level in the control of bladder function was examined in urethane anesthetized female rats. Methods Bladder activity was recorded via a transurethral catheter under isovolumetric conditions or via an intravesical catheter during continuous infusion cystometry. ZD7288, a selective I h channel inhibitor, was administered intrathecally at L6–S1 segmental levels of the spinal cord. Results Under isovolumetric conditions, intrathecal 0.3 µg of ZD7288 was inactive, whereas 1 and 3 µg abolished bladder activity for 5.6 ± 1.8 and 20.7 ± 3.9 min, respectively. Three micrograms also tended to decrease the amplitude of the contractions when they reappeared. During continuous cystometry, an intrathecal injection of ZD7288 at 0.3–3 µg dose‐dependently increased the intercontraction intervals by 7.5%, 33.1%, and 57.5% from pre‐drug values. A higher dose of ZD7288 (3 µg) tended to increase the pressure threshold for inducing micturition by 16.6% and the maximum voiding pressure by 11.1%. On the other hand, cardiovascular parameters such as heart rate and mean blood pressure were not affected by 0.3–3 µg of intrathecal ZD7288. Conclusions These results indicate that I h channels play an important role in the control of micturition. Because I h channel inhibition in the lumbosacral spinal cord reduced the frequency of the micturition reflex without significantly affecting the amplitude of reflex bladder contraction, I h channels might preferentially be involved in afferent processing in the spinal cord to control the micturition reflex. Neurourol. Urodynam. 27:838–844, 2008, © 2008 Wiley‐Liss, Inc.