Activation of serotonin 5-HT2C and 5-HT7 receptors enhances the urethral closure reflex during sneezing in rats

Suzuki T1, Shimizu T2, Kwon J2, Takaoka E2, Satoru Y2, Sumino Y2, Kitta T2, Miyazato M2, Miyake H3, Yoshimura N2

Research Type

Pure and Applied Science / Translational

Abstract Category

Female Stress Urinary Incontinence (SUI)

Abstract 485
Basic Science: Stress Urinary Incontinence and Benign Prostatic Hyperplasia
Scientific Podium Short Oral Session 27
Friday 31st August 2018
09:00 - 09:07
Hall D
Basic Science Incontinence Pharmacology
1. Department of Urology, Hamamatsu University School of Medicine, University of Pittsburgh, 2. University of Pittsburgh, 3. Department of Urology, Hamamatsu University School of Medicine
Presenter
Links

Abstract

Hypothesis / aims of study
The spinal serotonergic pathways have been reported to be involved in the control of urethral continence reflexes.  Previous study demonstrated that serotonin (5-HT) receptor subtypes, 5-HT1A or 5-HT2C, respectively, reduce or enhance the urethral continence reflex during sneezing in rats [1]. However, because there are other multiple excitatory and inhibitory 5-HT receptor subtypes, the overall effects of the 5-HT system or the subtype-specific mechanism in the control of the urethral function remain to be elucidated.  Moreover, 5-HT7 receptors are shown to be expressed in the spinal cord and dorsal root ganglia of rats [2] although the role of 5-HT7 receptors in the urethral continence reflex is not well elucidated. Therefore, in this study, we examined the impacts of 5-HT depletion induced by p-chlorophenylalanine (PCPA) and the effects of activation of 5-HT receptor subtypes such as 5-HT2C and 5-HT7 on urethral baseline activity and reflex contractions during sneezing in PCPA-pretreated rats.
Study design, materials and methods
Sixty adult female Sprague-Dawley rats weighing 228–270 g were used. We measured the amplitude of urethral pressure responses during sneezing (A-URS) and urethral baseline pressure (UBP) using a microtransducer-tipped catheter for 32 rats. We measured sneeze-induced leak point pressure (S-LPP), the lowest pressure value that induced fluid leakage from the urethral orifice for 28 rats.  Pre-drug sneeze-induced responses were measured before intravenous application of a 5-HT2C agonist (CP-809101), a 5-HT2C antagonist (SB-242084), a 5-HT1A antagonist (WAY-100635), a 5-HT7 agonist (LP44), and a 5-HT7 antagonist (SB-269970) in PCPA-pretreated rats. WAY-100635 was administered before LP44 administration to suppress the partial 5-HT1A effect of LP44. Data are expressed as mean ± standard error (SE). Unpaired t-test was used to compare the A-URS, UBP and Pabd between normal and PCPA-pretreated rats. Paired t-test was also used to compare the values before and after CP-809101 administration. One-way analysis of variance followed by Bonferroni’s multiple comparison tests were used to compare before and after administrations of multiple drugs. Statistical significance was set at P values < 0.05.
Results
1)	A-URS and UBP
Two-day pre-treatment of PCPA (n = 5) significantly decreased A-URS from 71.8 ± 7.1 to 36.8 ± 4.3 cmH2O (P < 0.01), and UBP from 31.1 ± 3.0 to 17.8 ± 2.2 cmH2O (P < 0.01) compared to normal rats (n = 6).  In PCPA-pretreated rats, CP-809101 (n = 4) or LP44 with pre-administration of WAY-100635 (5-HT1A antagonist) (n = 7) significantly increased A-URS from 42.1 ± 5.7 to 66.2 ± 6.5 cmH2O (P < 0.01) and 30.0 ± 2.7 to 50.5 ± 5.3 cmH2O (P < 0.01) and UBP from 17.3 ± 1.2 to 32.4 ± 2.7 cmH2O (P < 0.05) and 15.2 ± 1.6 to 26.6 ± 2.1 cmH2O (P < 0.01), respectively (Figure 1). The effects of CP-809101 and LP44 were antagonized by antagonists of each receptor subtype (SB-242084; n-=4 and SB-269970; n=6, respectively). The average values of sneeze-induced increases in Pabd measured by intra-abdominal catheters were not significantly different between normal and PCPA-pretreated rats or after injection of any drugs.
2)	S-LPP
Although SUI was not observed even at the highest intravesical pressure during sneezing of 108.8 ± 5.6 cmH2O in normal rats (n = 6), fluid leakage from the urethra during sneezing was observed with S-LPP values of 40.1 ± 2.5 cmH2O in all PCPA-pretreated rats (n = 6). In these 5-HT-depleted rats, fluid leakage from the urethra was still observed during sneezing after the treatment with CP-809101(n =4) or LP44 (n =6), which, however, significantly increased S-LPP by 28.0 cmH2O; from 39.7 ± 4.5 cmH2O to 67.7 ± 3.1 cmH2O (P < 0.01), and 15.2 cmH2O; from 37.8 ± 1.4 cmH2O to 53.0 ± 3.4 cmH2O (P < 0.01), respectively, compared to rats treated with PCPA alone. The effects of CP-809101 and LP44 were blocked by antagonists of each receptor subtype (n =3 each) (Figure 2).
Interpretation of results
In present study, we first examined the effect of PCPA because systemic pre-treatment of PCPA for 2 days reportedly resulted in 95 % depletion in brain 5-HT content [3]. Using this method, we clarified that PCPA treatment caused SUI during sneezing, indicating that the overall 5-HT system acts to maintain urinary continence. Furthermore, we examined the effects of 5-HT subtype-selective drugs (5-HT2C and 5-HT7) on urethral baseline activity and reflex contractions during sneezing in rats.
Concluding message
The results of this study indicate that activation of 5-HT receptors, as a whole, enhances the active urethral closure reflex during sneezing and that 5-HT2C and 5-HT7 receptors have facilitatory roles in urethral continence mechanisms in rats.
Figure 1
Figure 2
References
  1. Miyazato M, Kaiho Y, Kamo I, Kitta T, Chancellor MB, Sugaya K, Arai Y, de Groat WC, Yoshimura N. Role of spinal serotonergic pathways in sneeze-induced urethral continence reflex in rats. Am J Physiol Renal Physiol 297: F1024–F1031, 2009.
  2. Doly S, Fischer J, Brisorgueil MJ, Vergé D, Conrath M. Pre- and postsynaptic localization of the 5-HT7 receptor in rat dorsal spinal cord: immunocytochemical evidence. J Comp Neurol 26: 256-69, 2005.
  3. Yoshimura M, Hagimoto M, Matsuura T, Ohkubo J, Ohno M, Maruyama T, Ishikura T, Hashimoto H, Kakuma T, Yoshimatsu H, Terawaki K, Uezono Y, Toyohira Y, Yanagihara N, Ueta Y. Effects of food deprivation on the hypothalamic feeding-regulating peptides gene expressions in serotonin depleted rats. J Physiol Sci 64: 97–104, 2014.
Disclosures
Funding NIH R01-DK107450 Clinical Trial No Subjects Animal Species Rat Ethics Committee University of Pittsburgh
20/11/2024 17:29:13