Inhibitory effects of retigabine, a Kv7 channel activator, on mechanosensitive primary bladder afferent activities and nociceptive behaviors in rats.

AIMS: Kv7 voltage-gated potassium channels have been suggested to modulate mechano-afferent transduction and nociception in the bladder. We investigated the effects of retigabine, a Kv7 channel activator, on rhythmic bladder contractions (RBCs), and single-unit afferent activities (SAAs) of the primary bladder mechanosensitive afferent nerve fibers in urethane-anesthetized rats. In addition, the effects of pretreatment with retigabine on the nociceptive behaviors provoked by an intravesical instillation of resiniferatoxin (RTX) were evaluated in the conscious condition. METHODS: Female Sprague-Dawley rats were used. Under urethane anesthesia, saline was instilled into the bladder until RBCs were induced reproducibly. Then, the effects of intravenous, cumulative administrations of retigabine (0.1-3 mg/kg) or vehicle (saline) on RBCs were assessed. In separate animals, SAAs of Aδ- and C-fibers were identified by electrical stimulation of the pelvic nerve and by bladder distention with saline. After baseline recording, vehicle or retigabine (0.01-1 mg/kg) was administered intravenously and further recordings were performed. Under pretreatment with vehicle or retigabine (3 mg/kg intraperitoneally), the frequencies of lower abdominal licking and freezing were counted and scored as the bladder nociceptive behaviors induced by intravesical RTX instillation (3 µM, 0.3 ml). RESULTS: Retigabine dose-dependently decreased both the frequency and the amplitude of RBCs and SAAs of both Aδ- and C-fibers. The effect on RBCs was more potent on the frequency than the amplitude. Retigabine inhibited the RTX-induced abdominal licking, but not freezing. CONCLUSION: Kv7 channels are likely to be implicated in inhibition of bladder mechano- and nociceptive sensory transduction. Neurourol. Urodynam. 36:280-285, 2017. © 2015 Wiley Periodicals, Inc.

Neuromedin B Restores Erectile Function by Protecting the Cavernous Body and the Nitrergic Nerves from Injury in a Diabetic Rat Model.

Erectile dysfunction (ED) is a major health problem worldwide and affects approximately 75% of diabetic patients, likely due to severely damaged cavernous body. While screening for cytokines produced by adipose tissue-derived stem cells, we detected neuromedin B (NMB). To explore a potential treatment option for ED, we examined whether NMB was capable of restoring erectile function. We also examined the potential mechanism by which NMB could restore erectile function. Male Wistar rats were injected with streptozotocin (STZ) to induce diabetes. An adenovirus expressing NMB (AdNMB) was injected into the penis 6 weeks after STZ administration. Four weeks after the injection of AdNMB, erectile function, penile histology, and protein expression were analyzed. As assessed by the measurement of intracavernous pressure, AdNMB injection significantly restored erectile function compared with the injection of an adenovirus expressing green fluorescent protein. This restoration was associated with conservation of the cavernous body structure and neural nitric oxide synthase (nNOS)-expressing nerves, together with recovery of α-smooth muscle actin, vascular endothelial-cadherin, and nNOS expression. Furthermore, NMB significantly stimulated the survival of SH-SY5Y cells derived from human neuroblastoma tissue with characteristics similar to neurons. Collectively, these results suggested that NMB restored erectile function via protection of the cavernous body from injury and stimulation of the survival of the associated nerves. NMB may be useful to treat ED patients with a severely damaged cavernous body.

Senescent Cells Impair Erectile Function through Induction of Endothelial Dysfunction and Nerve Injury in Mice.

Erectile dysfunction (ED) is a major health problem, particularly in the elderly population, which is rapidly increasing. It is necessary to elucidate the mechanism by which ED occurs in the elderly. Cellular senescence is commonly detected in old tissues, and it is well known that senescent cells not only withdraw from the cell cycle but also remain viable and actively produce a variety of cytokines. We examined the effect of senescent cells on erectile function after injection of senescent cells into the penises of mice. Human umbilical vein endothelial cells were infected with an adenovirus expressing a constitutively active mutant of Ras to induce senescence, and were injected into the penises of nude mice. These senescent cells expressed proinflammatory cytokines such as interleukin-1ß (IL-1ß). Injection of senescent cells impaired erectile function, as assessed by the measurement of intracavernous pressure. Although the structure of the cavernous body did not remarkably change, expression of the catalytically active form of endothelial nitric oxide synthase and that of total neural nitric oxide synthase significantly decreased after injection. The penises injected with the senescent cells expressed human IL-1ß and subsequently endogenous proinflammatory cytokines such as mouse IL-1ß and tumor necrosis factor-α. These results suggested that senescent cells impaired erectile function through induction of endothelial dysfunction and nerve injury. These effects may be mediated by proinflammatory cytokines produced by senescent cells.

Changes in the function and expression of T-type and N-type calcium channels in the rat bladder after bladder outlet obstruction.

PURPOSE: We evaluated possible changes in the function and expression of T-type and N-type Ca(2+) channels in the bladder of rats with bladder outlet obstruction. MATERIALS AND METHODS: Female Sprague Dawley® rats were divided into a group with bladder outlet obstruction created by partial urethral ligation and a sham operated group. Six weeks postoperatively we determined the mRNA expression of T-type and N-type Ca(2+) channels in the bladder, dorsal root ganglion and spinal cord. We also cystometrically investigated expression by intravenous administration of the T-Ca blocker RQ-00311610 or the N-type Ca(2+) channel blocker ω-conotoxin GVIA. We then performed in vitro functional studies of detrusor strips using these blockers. RESULTS: mRNA expression of T-type Ca(2+) channels in the bladder detrusor and mucosa layers, and the spinal cord dorsal horn, and N-type Ca(2+) channels in the whole bladder and detrusor layer, and the spinal cord dorsal horn was greater in the obstructed group than the sham operated group. In obstructed rats bladder capacity and voided volume increased after RQ-00311610 administration but the number of nonvoiding contractions decreased after ω-conotoxin GVIA administration. Detrusor strips from obstructed rats showed weaker contractile responses to electrical field stimulation, particularly in regard to the purinergic component. ω-Conotoxin GVIA suppressed electrical field stimulation induced contractions only in the detrusor of obstructed rats, especially the cholinergic component. CONCLUSIONS: Blocking T-type Ca(2+) channels increased bladder capacity while N-type Ca(2+) channel blockade inhibited nonvoiding contractions in rats with bladder outlet obstruction. Decreased bladder efferent neurotransmission occurred after bladder outlet obstruction, predominantly in its purinergic component and detrusor contractions via cholinergic neurotransmission were activated in a compensatory manner, probably via N-type Ca(2+) channel up-regulation.

Prenatal stress induces anxiety-like behavior together with the disruption of central serotonin neurons in mice.

Most pregnant women are at risk of showing some emotional abnormality, since some biological functions such as hormonal systems may dramatically change in pregnancy. Some of them may be exposed to strong stress as hesitation of positive drug therapies because of worries regarding adverse effects on the embryo. A growing body of evidence suggests that prenatal stress increases the vulnerability to neuropsychiatric disorders, including depression and anxiety. However, the mechanisms involved are still unknown. To clarify the influence of exposure to prenatal stress on emotional development, we examined behavioral responses in offspring exposed to weak- or strong-prenatal restraint stress. We found that offspring that had been exposed to strong stress displayed anxiety-like behavior as determined by the elevated plus-maze test. It has been widely accepted that central serotonin (5-hydroxytryptamine; 5-HT) neurons play a critical role in emotional behaviors. Immunohistochemical studies showed that exposure to strong-prenatal restraint stress increased the expression of 5-HT-positive cells in the dorsal raphe nuclei in mice. Moreover, under these conditions, tryptophan hydroxylase-like immunoreactivities were also dramatically increased. In contrast, these behavioral and neurochemical abnormalities were not observed in offspring that had been exposed to weak-prenatal restraint stress. These findings indicate that exposure to excessive prenatal stress induces anxiety-like behavior together with disruption of the development of 5-HT neurons in mice.