Calcitonin gene-related peptide and substance P induce pronounced motor effects in the female rat urethra in vivo

Effects of Calcitonin-Gene-Related-Peptide on Auditory Nerve Activity

Calcitonin-gene-related peptide (CGRP) is a lateral olivocochlear (LOC) efferent neurotransmitter. Depression of sound-driven auditory brainstem response amplitude in CGRP-null mice suggests the potential for endogenous CGRP release to upregulate spontaneous and/or sound-driven auditory nerve (AN) activity. We chronically infused CGRP into the guinea pig cochlea and evaluated changes in AN activity as well as outer hair cell (OHC) function. The amplitude of both round window noise (a measure of ensemble spontaneous activity) and the synchronous whole-nerve response to sound (compound action potential, CAP) were enhanced. Lack of change in both onset adaptation and steady state amplitude of sound-evoked distortion product otoacoustic emission (DPOAE) responses indicated CGRP had no effect on OHCs, suggesting the origin of the observed changes was neural. Combined with results from the CGRP-null mice, these results appear to confirm that endogenous CGRP enhances auditory nerve activity when released by the LOC neurons. However, infusion of the CGRP receptor antagonist CGRP (8–37) did not reliably influence spontaneous or sound-driven AN activity, or OHC function, results that contrast with the decreased ABR amplitude measured in CGRP-null mice.

Neuropeptides in the urinary tract of male sheep lambs

Small ruminants are often presumed to be at a higher risk of developing obstructive urolithiasis after early castration. However, the underlying pathophysiology and histological correlation of this assumption is unknown. This study examines the neuropeptide distribution of the lower urinary tract in male lambs in respect to castration status or a recent history of obstructive urolithiasis. Various tissue samples were taken and examined. The sample consisted of 34 male lambs, aged six months (n = 11 early and n = 11 late castration; n = 12 intact), and 8 rams that had undergone necropsy due to fatal outcome after obstructive urolithiasis. Immunohistochemical stainings for substance P (SP), vasoactive intestinal polypeptide (VIP) and neurofilaments (NF) were performed and compared between the groups. A significant reduction in immunoreactive signals of SP, VIP and NF was evident in the urolithiasis group (SP and NF: P < 0.0001; VIP: P = 0.02). The results of immunohistochemistry suggest that castration had no effect on the content of neuropeptides, as well as the innervation density of the urethra in the male lambs. In the case of. obstructive urolithiasis, the pattern of neuropeptide distribution was severely disturbed and cell damage lead to a reduction in detectable periurethral bundles of nerve fibers. The severe tissue damage was assumed to have a negative impact on the outcome of treatment, leading to complications such as urethral strictures. These, in turn, often result in relapses.

Expression and distribution of phosphodiesterase isoenzymes in the human male urethra

OBJECTIVE

To investigate the expression and distribution of phosphodiesterase (PDE) isoenzymes PDE1A, PDE2A, PDE4A, PDE4B, and PDE5A in human urethral tissue.

METHODS

Specimens of penile urethra were obtained from male subjects who had undergone male-to-female sex reassignment surgery. Using immunohistochemistry (immunofluorescence), the occurrence of PDE1A, PDE2A, PDE4A, PDE4B, and PDE5A, the neuronal nitric oxide synthase, calcitonin gene-related peptide, and vasoactive intestinal polypeptide was examined in urethral sections. Cytosolic supernatants prepared from isolated human urethral tissue were subjected to Western blot analysis using specific anti-PDE antibodies.

RESULTS

Immunosignals specific for PDE1A, 4A, 4B, and 5A were observed in the urethral smooth musculature. The smooth muscle bundles were seen innervated by slender nerve fibers, characterized by the expression of the neuronal nitric oxide synthase, calcitonin gene-related peptide, and vasoactive intestinal polypeptide. The expression of the PDE isoenzymes mentioned was confirmed by Western blotting.

CONCLUSION

The results provide evidence for a significance of both the cyclic adenosine monophosphate and cyclic guanosine monophosphate signaling in the control of human urethral smooth muscle. The selective inhibition of PDE isoenzymes might represent a pharmacologic option to influence the function of smooth musculature in the human outflow region.

Exogenously administered bombesin and gastrin releasing peptide contract the female rat urethra in vivo and in vitro

BACKGROUND

Bombesin (BOM) and gastrin releasing peptide (GRP) have been located to the lower urinary tract. However, there is a paucity of data demonstrating the impact of these neuropeptides.

OBJECTIVES

The present study investigates the impact of BOM and GRP in the female Sprague-Dawley rats 225  g b.w. n = 37 urethras in vitro and in vivo. Intraurethral pressure was recorded by a catheter placed at the maximum pressure zone corresponding to the intrinsic urethral spincter.

MEASUREMENTS

In vitro, the intraurethral pressure was measured in response to the administration of BOM and GRP and noradrenaline from perfused intact urethral/bladder preparations. In vivo, changes in intraurethral pressure were conducted in anesthetized subjects and compared with the basal intraurethral pressure and sham controls.

RESULTS

In vitro, the increase in intraurethral pressure induced by BOM was 23.6 ± 3.2  cmH(2) O, exceeding the pressure evoked with NA by 10.7  cmH(2) O whereas GRP induced 10.7 ± 1.6  cmH(2) O, an increase of 3.3 cmH(2) O but less than the NA evoked intraurethral pressure by 2.2  cmH(2) O. Incubation with scopolamine (1 µM), phentolamine (1  µM), pancuronium (1  µM), and indomethacin (1  µM) did not produce any significant difference in the contractile responses to BOM or GRP. In vivo, the mean basal pressure was 22.9 ± 1.4  cmH(2) O. The intraurethral pressure evoked by BOM was 29.7  cmH(2) O (21.3  ±  1.3 to 51.0  ±  1.6  cmH(2) O), and for GRP, the evoked intraurethral pressure was 33.8  cmH(2) O (22.3  ±  1.9 to 56.2  ±  30  cmH(2) O).

CONCLUSIONS

BOM and GRP may contribute to the control of continence by their contractile action on the sphincters of the lower urinary tract outflow region.

Role of central calcitonin gene-related peptide (CGRP) in locomotor and anxiety- and depression-like behaviors in two mouse strains exhibiting a CGRP-dependent difference in thermal pain sensitivity

We have previously shown that, in AKR and C57BL/6 mice, a genetic polymorphism results in differential expression of the peptide, calcitonin gene-related polypeptide (CGRP), explaining a strain difference in thermal pain sensitivity. Although CGRP is widely distributed in the brain, little is known about the effects of supraspinal CGRP. We used AKR and C57BL/6 mice as a model to explore the effects of centrally (intracerebroventricular) injected CGRP and the CGRP receptor antagonists, CGRP(8-37) and BIBN4096BS, in a series of behavioral assays. Locomotor activity was significantly increased in C57BL/6 mice following the injection of BIBN4096BS and in both strains after the administration of CGRP(8-37) into the third ventricle. CGRP increased paw-withdrawal latencies in C57BL/6 mice only, while decreasing depression-like behaviors in both strains in the forced-swimming test. CGRP and CGRP receptor antagonists failed to modulate activity in the elevated plus maze, a model of anxiety. Taken together, these results suggest a complex role for supraspinal CGRP systems in the regulation of locomotion, nociception, and depression-like behaviors.

Abnormal urethral motor function is common in female stress, mixed, and urge incontinence

AIM

To investigate the urethral motor function in incontinent women.

MATERIALS AND METHODS

The intraurethral pressure was measured continuously in the high-pressure zone of the urethra at rest and during repeated short squeezes around the microtip transducer catheter in a group of 205 women with clinically manifest urinary incontinence (severe), and compared with the findings of investigations in 87 middle-aged women (53-63 years) with treatment naïve incontinence (mild-to-moderate) and healthy controls.

RESULTS

Women with established incontinence significantly (P < 0.001) more often (66%) had a pressure fall during or immediately following squeeze than women with treatment naïve incontinence (35%) or asymptomatic women (25%). The acceleration of urinary flow and the maximal flow rate were significantly (P < 0.01) increased in patients with incontinence: acceleration was 13 +/- 2.2 (17.8), 20 +/- 2.8 (18.9), and 32 +/- 4.9 (24.9) degrees (mean +/- SEM; SD) for incontinence, naïve incontinence and no incontinence, respectively; maximum urinary flow rate was 23, 22, and 16 ml/sec. No statistical differences in any of these measures were seen when stress and urge incontinence were compared.

CONCLUSION

Women with stress, urge, and mixed urinary incontinence seem to have a primary neuromuscular disorder in the urethra, which presents itself as an overactive opening mechanism with a urethral pressure fall instead of a pressure increase on provocation during the filling phase of the bladder, and during bladder emptying a more efficient opening of the bladder outlet than in normal women. We suggest that one and the same pathophysiological mechanism participates in female stress, urge, and mixed incontinence.

Tachykinins and tachykinin receptors: effects in the genitourinary tract

Tachykinins (TKs) are a family of peptides involved in the central and peripheral regulation of urogenital functions through the stimulation of TK NK1, NK2 and NK3 receptors. At the urinary system level, TKs locally stimulate smooth muscle tone, ureteric peristalsis and bladder contractions, initiate neurogenic inflammation and trigger local and spinal reflexes aimed to maintain organ functions in emergency conditions. At the genital level, TKs are involved in smooth muscle contraction, in inflammation and in the modulation of steroid secretion by the testes and ovaries. TKs produce vasodilatation of maternal and fetal placental vascular beds and appear to be involved in reproductive function, stress-induced abortion, and pre-eclampsia. The current data suggest that the genitourinary tract is a primary site of action of the tachykininergic system.

Inhibitory actions of calcitonin gene-related peptide and capsaicin: evidence for local axonal reflexes in the bladder wall

OBJECTIVES

To explore the actions of capsaicin and the neurotransmitters released by capsaicin (substance P and calcitonin gene-related peptide, CGRP) on the phasic contractile activity generated in the whole isolated guinea pig bladder by muscarinic stimulation, and to examine the hypothesis that collateral fibres of sensory axons contribute to a local reflex in the bladder wall.

MATERIALS AND METHODS

All experiments used whole isolated bladders from female guinea pigs (270-300 g). Bladders were cannulated via the urethra to measure intravesical pressure and suspended in a heated chamber containing oxygenated Tyrode's solution at 33-35 degrees C. All drugs were added to the solution bathing the abluminal surface.

RESULTS

Application of capsaicin (10 micromol/L) to the whole isolated bladder resulted in complex changes in the frequency and amplitude of phasic activity generated by muscarinic stimulation; an initial burst of activity involving a rise in frequency, a second phase of reduced amplitude and frequency and a third phase where the amplitude of the transients recovered and the frequency increased. Capsaicin had no effect on the phasic activity generated by the nicotinic ligand lobeline (30 micromol/L). As capsaicin releases the neurotransmitter content of the sensory nerves, experiments explored the actions of CGRP and substance P on the muscarinic-induced activity. CGRP (3-30 nmol/L) reduced the amplitude and slowed the frequency of the phasic activity. On washing off CGRP the amplitude and frequency of the transient activity recovered and there was a transient increase in frequency above the levels before stimulation. There was also evidence of a desensitization to CGRP on repeated application. In contrast, substance P (100-300 nmol/L) increased the frequency of the transients, while on removing it there was an inhibition of both amplitude and frequency.

CONCLUSIONS

These results suggest that neurotransmitters released from sensory nerve endings in the guinea pig bladder wall affect phasic activity. The direct application of CGRP inhibited phasic activity while substance P was excitatory, indicating the specific contributions of these neurotransmitters. The excitation after stimulation with CGRP and inhibition with substance P may indicate that these neurotransmitters feed back on the sensory nerves to induce transmitter release. Taken together, these observations suggest the presence of a local reflex in the bladder wall, where axon collaterals of afferent sensory fibres innervate the pacemaker mechanism in the bladder wall responsible for generating phasic activity. The possible importance of this reflex in the physiology and pathophysiology of the bladder is discussed.