Functional, biochemical and anatomical changes in the rat urinary bladder induced by perigangliar injection of colchicine

Effects of early intravesical administration of resiniferatoxin to spinal cord-injured rats in neurogenic detrusor overactivity

OBJECTIVES

To investigate if intravesical administration during spinal shock of resiniferatoxin (RTX), an ultrapotent desensitizing agonist of transient receptor potential vanilloid-1 (TRPV1), would silence TRPV1-expressing bladder afferents at an early stage of disease progression and modulate neurogenic detrusor overactivity (NDO) emergence.

MATERIALS AND METHODS

Rats submitted to largely incomplete spinal cord transection at T8/9 spinal segment were treated with intravesical RTX (50 nM) or its vehicle during spinal shock. Four weeks after spinal lesion, bladder-reflex activity was evaluated by cystometry under urethane anesthesia, after which the bladder, spinal cord, and dorsal root ganglia were collected and processed.

RESULTS

We found improvements on bladder function several weeks after early intravesical RTX administration, including a marked decrease of intravesical pressures and amplitude of bladder contractions. Such strong long-lasting urodynamic effects resulted from the very potent desensitizing activity of RTX on peripheral terminals of sensory afferents, an effect restricted to the bladder.

CONCLUSION

Our results support that an early intervention with RTX could potentially attenuate NDO development and ensuing urinary incontinence, with a dramatic impact on the quality of life of spinal cord injury patients.

Sonic hedgehog, apoptosis, and the penis

INTRODUCTION

Smooth muscle apoptosis in the penis is common in prostatectomy patients and animal models of erectile dysfunction (ED). A critical regulator of smooth muscle apoptosis in the penis is the secreted protein Sonic hedgehog (SHH). Since SHH protein treatment of the penis prevents cavernous nerve (CN) injury-induced apoptosis, SHH has the potential to treat post-prostatectomy apoptosis. However, little is known about how SHH signaling is regulated in the adult penis.

AIM

The goal of this review is to examine what is known about SHH signaling in the penis, to offer insight as to how SHH inhibition induces apoptosis in penile smooth muscle, and to define the role of the SHH pathway in maintaining CN integrity.

METHODS

Information presented in this review was derived from a literature search using the National Library of Medicine PubMed Services. Search terms included SHH, apoptosis, smooth muscle, penis, ED, pelvic ganglia, corpora cavernosa, CN, regeneration, Schwann cell, neural activity, and transport.

RESULTS

In this review, we have discussed the role of the CN in regulation of SHH abundance and apoptosis induction in the penis, and have examined the function and localization of SHH signaling in the CN.

CONCLUSION

There is substantial potential to develop SHH for delivery to the penis of prostatectomy patients at the time of surgery in order to prevent apoptosis induction and long-term ED development. Studies are in progress that will identify if SHH may be used as a regenerative therapy to speed CN regeneration.

Neural influences on sonic hedgehog and apoptosis in the rat penis

The role of sonic hedgehog (SHH) in maintaining corpora cavernosal morphology in the adult penis has been established; however, the mechanism of how SHH itself is regulated remains unclear. Since decreased SHH protein is a cause of smooth muscle apoptosis and erectile dysfunction (ED) in the penis, and SHH treatment can suppress cavernous nerve (CN) injury-induced apoptosis, the question of how SHH signaling is regulated is significant. It is likely that neural input is involved in this process since two models of neuropathy-induced ED exhibit decreased SHH protein and increased apoptosis in the penis. We propose the hypothesis that SHH abundance in the corpora cavernosa is regulated by SHH signaling in the pelvic ganglia, neural activity, or neural transport of a trophic factor from the pelvic ganglia to the corpora. We have examined each of these potential mechanisms. SHH inhibition in the penis shows a 12-fold increase in smooth muscle apoptosis. SHH inhibition in the pelvic ganglia causes significantly increased apoptosis (1.3-fold) and decreased SHH protein (1.1-fold) in the corpora cavernosa. SHH protein is not transported by the CN. Colchicine treatment of the CN resulted in significantly increased smooth muscle apoptosis (1.2-fold) and decreased SHH protein (1.3-fold) in the penis. Lidocaine treatment of the CN caused a similar increase in apoptosis (1.6-fold) and decrease in SHH protein (1.3-fold) in the penis. These results show that neural activity and a trophic factor from the pelvic ganglia/CN are necessary to regulate SHH protein and smooth muscle abundance in the penis.

Neuropeptide Y inhibits axonal transport of particles in neurites of cultured adult mouse dorsal root ganglion cells

Neuropeptide Y (NPY) plays a modulatory role in processing nociceptive information. The present study investigated the effects of NPY on axonal transport of particles in neurites of cultured adult dorsal root ganglion (DRG) cells using video-enhanced microscopy. Application of NPY decreased the number of particles transported in both the anterograde and retrograde directions. This effect was persistently observed during NPY application and was reversed after washout. The inhibitory effect of NPY was concentration dependent between 10(-9) M and 10(-6) M. The instantaneous velocity of individual particles moving in anterograde and retrograde directions was also reduced by NPY. Both the NPY Y1 receptor agonist [Leu31,Pro34]-NPY and NPY Y2 receptor agonist NPY(13-36) mimicked the effect of NPY on the number of transported particles. An immunocytochemical study using an antiserum against the NPY Y1 receptor protein revealed that the Y1 receptor was expressed in the majority (85.9 %) of cultured adult mouse DRG cells. Pre-treatment of cells with pertussis toxin, a GTP-binding protein (G protein) inhibitor, completely blocked the inhibitory effect of NPY. Each application of SQ-22536, an adenylate cyclase inhibitor, and H-89, a protein kinase A inhibitor, mimicked and occluded the effect of NPY. In contrast, dibutyryl cAMP (dbcAMP), a membrane permeable cAMP analogue, and forskolin, an activator of adenylate cyclase, produced a transient increase in axonal transport. The application of dbcAMP and forskolin in combination with NPY negated the effect of NPY alone. These results suggest that NPY, acting at Y1 and Y2 receptors, inhibits axonal transport of particles in sensory neurones. The effect seems to be mediated by a pertussis toxin-sensitive G protein, adenylate cyclase, and protein kinase A pathway. Therefore, NPY may be a modulatory factor for axonal transport in sensory neurones.