Central deficiency of norepinephrine synthesis and norepinephrinergic neurotransmission contributes to seizure-induced respiratory arrest.

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of mortality in patients with intractable epilepsy. However, the pathogenesis of SUDEP seems to be poorly understood. Our previous findings showed that the incidence of seizure-induced respiratory arrest (S-IRA) was markedly reduced by atomoxetine in a murine SUDEP model. Because the central norepinephrine α-1 receptor (NEα-1R) plays a vital role in regulating respiratory function, we hypothesized that the suppression of S-IRA by atomoxetine was mediated by NE/NEα-1R interactions that can be reversed by NEα-1R antagonism. We examined whether atomoxetine-mediated suppression of S-IRA evoked by either acoustic stimulation or pentylenetetrazole (PTZ) in DBA/1 mice can be reversed by intraperitoneal (IP) and intracerebroventricular (ICV) administration of prazosin, a selective antagonist of NEα-1R. The content and activity of tyrosine hydroxylase (TH), a rate-limiting enzyme for NE synthesis, in the lower brainstem was measured by ELISA. Electroencephalograms (EEG) were obtained from using the PTZ-evoked SUDEP model. In our models, atomoxetine-mediated suppression of S-IRA evoked by either acoustic stimulation or PTZ was significantly reversed by low doses of IP and ICV prazosin. Neither repetitive acoustic stimulation nor S-IRA reduced TH levels in lower brainstem. However, the enzyme activity of TH levels in lower brainstem was significantly increased by mechanical ventilation with DBA/1 mice, which makes the dying DBA/1 mice suffering from S-IRA and SUDEP recover. EEG data showed that although the protective effect of atomoxetine was reversed by prazosin, neither drug suppressed EEG activity. These data suggest that deficient synthesis of NE and norepinephrinergic neurotransmission contributed to S-IRA and that the NEα-1R is a potential therapeutic target for the prevention of SUDEP.

The α1-adrenoceptor inhibitor ρ-TIA facilitates net hunting in piscivorous Conus tulipa.

Cone snails use separately evolved venoms for prey capture and defence. While most use a harpoon for prey capture, the Gastridium clade that includes the well-studied Conus geographus and Conus tulipa, have developed a net hunting strategy to catch fish. This unique feeding behaviour requires secretion of "nirvana cabal" peptides to dampen the escape response of targeted fish allowing for their capture directly by mouth. However, the active components of the nirvana cabal remain poorly defined. In this study, we evaluated the behavioural effects of likely nirvana cabal peptides on the teleost model, Danio rerio (zebrafish). Surprisingly, the conantokins (NMDA receptor antagonists) and/or conopressins (vasopressin receptor agonists and antagonists) found in C. geographus and C. tulipa venom failed to produce a nirvana cabal-like effect in zebrafish. In contrast, low concentrations of the non-competitive adrenoceptor antagonist ρ-TIA found in C. tulipa venom (EC50 = 190 nM) dramatically reduced the escape response of zebrafish larvae when added directly to aquarium water. ρ-TIA inhibited the zebrafish α1-adrenoceptor, confirming ρ-TIA has the potential to reverse the known stimulating effects of norepinephrine on fish behaviour. ρ-TIA may act alone and not as part of a cabal, since it did not synergise with conopressins and/or conantokins. This study highlights the importance of using ecologically relevant animal behaviour models to decipher the complex neurobiology underlying the prey capture and defensive strategies of cone snails.

Evolution in the Risk of Cataract Surgical Complications among Patients Exposed to Tamsulosin: A Population-Based Study.

PURPOSE: Tamsulosin is associated with intraoperative floppy iris syndrome (IFIS), an important risk factor for complications during cataract surgery. Significant efforts have been made to increase awareness of the risks associated with tamsulosin, and educational initiatives have fostered the uptake of technical adjustments to decrease adverse event rates among tamsulosin-exposed patients. However, the effectiveness of these efforts at the population level has not been studied. DESIGN: Population-based study to evaluate cataract surgical adverse event rates over time among patients exposed to tamsulosin and those not exposed to this drug. PARTICIPANTS: All male patients 66 years of age and older undergoing cataract surgery in Ontario, Canada, between January 1, 2003, and December 31, 2013, were included in the study. METHODS: Linked healthcare databases were used to study the evolution in the risk of cataract surgical adverse events over time among tamsulosin-exposed and non-tamsulosin-exposed patients adjusting for patient-, surgeon-, and institution-level covariates. The study timeframe incorporated periods before and after the first reports of tamsulosin-associated IFIS. MAIN OUTCOME MEASURES: Four important cataract surgical adverse events were evaluated: posterior capsule rupture, dropped lens fragments, retinal detachment, and suspected endophthalmitis. RESULTS: Among patients exposed to tamsulosin, the risk of surgical adverse events decreased over time (odds ratio, 0.95 per year; 95% confidence interval, 0.91-0.99 per year). This trend was observed across patient age strata. Among patients not recently exposed to tamsulosin, the risk of surgical adverse events also decreased over time (odds ratio, 0.96 per year; 95% confidence interval, 0.95-0.98 per year). CONCLUSIONS: The risk of cataract surgical complications among both tamsulosin-exposed and non-tamsulosin-exposed patients declined between 2003 and 2013. Tamsulosin remains an important risk factor for cataract surgical adverse events, and ongoing efforts will be needed to develop and disseminate surgical approaches that mitigate the risks posed by tamsulosin.

In vivo metabolic investigation of silodosin using UHPLC-QTOF-MS/MS and in silico toxicological screening of its metabolites.

Silodosin (SLD) is a novel α1-adrenoceptor antagonist which has shown promising clinical efficacy and safety in patients with benign prostatic hyperplasia (BPH). However, lack of information about metabolism of SLD prompted us to investigate metabolic fate of SLD in rats. To identify in vivo metabolites of SLD, urine, feces and plasma were collected from Sprague-Dawley rats after its oral administration. The samples were prepared using an optimized sample preparation approach involving protein precipitation followed by solid-phase extraction and then subjected to LC/HR-MS/MS analysis. A total of 13 phase I and six phase II metabolites of SLD have been identified in rat urine which includes hydroxylated, N-dealkylated, dehydrogenated, oxidative, glucosylated, glucuronide and N-sulphated metabolites, which are also observed in feces. In plasma, only dehydrogenated, N-dealkylated and unchanged SLD are observed. The structure elucidation of metabolites was done by fragmentation in MS/MS in combination with HRMS data. The potential toxicity profile of SLD and its metabolites were predicted using TOPKAT software and most of the metabolites were proposed to show a certain degree of skin sensitization and occular irritancy. Copyright © 2016 John Wiley & Sons, Ltd.

Terazosin-induced alterations in catalase expression and lipid peroxidation in the rat seminal vesicles.

Previous studies have shown that alpha1-adrenergic receptor antagonists may alter seminal vesicle contractility and impair fertility in male rats. This study was designed to investigate the effects of terazosin on the catalase expression in the seminal vesicles and the lipid peroxidation of the seminal fluid in normal adult rats. Wistar rats were treated with terazosin (1.2 mg kg(-1) body weight, given orally every second day) for 120 days. Catalase expression was assessed immunohistochemically in tissue sections of the seminal vesicles, and lipid peroxidation was estimated by measuring the malondialdehyde (MDA) levels in the seminal vesicles' fluid. The seminal vesicles in terazosin-treated rats were particularly distended in comparison with those of controls, and their secreting epithelium was suppressed. Cytoplasmic catalase expression in the secreting epithelial cells (% of cells) was increased in terazosin-treated specimens in comparison with controls (76.1 ± 17.1 versus 51.3 ± 25.1, P = 0.005). MDA levels (µm) were also higher in samples from treated subjects in comparison with controls (2.67 ± 1.19 versus 1.39 ± 0.19, P = 0.01). Although the direct effect of terazosin treatment on the seminal vesicles is that of impaired contractility, an indirect effect is that on fertility by increasing lipid peroxidation in the seminal fluid and/or through degrading of hydrogen peroxide that is essential for sperm capacitation.