The use of alpha-adrenoceptor antagonists in the pharmacological management of benign prostatic hypertrophy: an overview

Isolated angioedema due to face mask and other cases of isolated angioedema

Isolated angioedema can be divided into two groups as mast cell-mediated angioedema and bradykinin-mediated angioedema according to the known mechanisms of occurrence. However, angioedema can also occur with mechanisms whose cause is unknown. Treatment varies according to the mechanism of angioedema formation. In this prospective study, we present the causes of 80 isolated angioedema cases admitted to our clinic during the pandemic period. We would like to emphasize the causes that we found in our cases but which are rare in the literature. For example: angioedema due to allergy to nickel in the mask used during the pandemic period, T cell-mediated angioedema, alpha adrenergic receptor blocker use, and patients diagnosed with collagen tissue disease presenting with angioedema as the first clinical finding.

Discovery Methodology of Novel Conotoxins from Conus Species

Cone snail venoms provide an ideal resource for neuropharmacological tools and drug candidates discovery, which have become a research hotspot in neuroscience and new drug development. More than 1,000,000 natural peptides are produced by cone snails, but less than 0.1% of the estimated conotoxins has been characterized to date. Hence, the discovery of novel conotoxins from the huge conotoxin resources with high-throughput and sensitive methods becomes a crucial key for the conotoxin-based drug development. In this review, we introduce the discovery methodology of new conotoxins from various Conus species. It focuses on obtaining full N- to C-terminal sequences, regardless of disulfide bond connectivity through crude venom purification, conotoxin precusor gene cloning, venom duct transcriptomics, venom proteomics and multi-omic methods. The protocols, advantages, disadvantages, and developments of different approaches during the last decade are summarized and the promising prospects are discussed as well.

Treatment of Post-Traumatic Stress Disorders with the Alpha-1 Adrenergic Antagonist Prazosin

OBJECTIVE

The present review aims to assess the clinical efficacy and safety of the α-1-adrenergic antagonist prazosin as primary pharmacologic treatment for post-traumatic stress disorder (PTSD).

METHOD

A systematic review was performed using keywords (i.e., prazosin, α-1-adrenergic antagonist, α-1-blocker, post-traumatic stress disorder) in the databases PubMed/Medline (1966-May 2016), Embase (1966-May 2016), ScienceDirect (1823-May 2016), OvidSP (1946-May 2016) and Nature (1845-May 2016). To be considered for inclusion, studies had to test the efficacy of prazosin either alone or added to ongoing treatment in adults with PTSD, use validated tools to assess and monitor the disorders, allow comparisons on the basis of univariate analyses (i.e., p-values of t-tests and effect sizes) and list the identified adverse reactions.

RESULTS

12 studies were included: 5 randomized controlled trials, 4 open-label prospective trials and 3 retrospective file reviews. The evaluation concerned 276 patients exposed to civilian trauma (19%) or war trauma (81%). Prazosin significantly decreases trauma nightmares, avoidance, hypervigilance and improves patient status in all studies. No significant difference of blood pressure was observed at the end of trials.

CONCLUSIONS

Beyond the methodological and clinical biases of these studies, the present review not only confirms the effectiveness and good tolerability of prazosin, but also suggests its possible use as primary pharmacologic treatment for PTSD. Uncertainties remain, however, regarding the prescription modalities and dosages.

Prazosin Reduces Alcohol Intake in an Animal Model of Alcohol Relapse

BACKGROUND

Many alcoholics and heavy drinkers undergo repeated cycles of alcohol abstinence followed by relapse to alcohol drinking; a pattern that contributes to escalated alcohol intake over time. In rodents, alcohol drinking that is interspersed with periods of alcohol deprivation (imposed abstinence) increases alcohol intake during reaccess to alcohol. This is termed the "alcohol deprivation effect" or "ADE" and is a model of alcohol relapse in humans. We have previously reported that prazosin reduces alcohol drinking during both brief and prolonged treatment in rats selectively bred for alcohol preference ("P" rats). This study explores whether prazosin prevents alcohol "relapse" in P rats, as reflected by a reduced or abolished ADE.

METHODS

Adult male P rats were given 24-hour access to food and water and scheduled access to alcohol (15 and 30% v/v solutions presented concurrently) for 2 h/d. After 5 weeks, rats underwent imposed alcohol deprivation for 2 weeks, followed by alcohol reaccess for 2 weeks, and this pattern was repeated for a total of 3 cycles. Rats were injected with prazosin (0, 0.5, 1.0, or 2.0 mg/kg body weight, intraperitoneally) once a day for the first 5 days of each alcohol reaccess cycle.

RESULTS

Alcohol intake increased on the first day of each alcohol reaccess cycle, demonstrating the formation of an ADE. The ADE was short-lived, lasting only 1 day, during each of the 3 cycles. Prazosin, in all doses tested, prevented the expression of an ADE in all 3 alcohol reaccess cycles.

CONCLUSIONS

Prazosin decreases alcohol intake in P rats even in a situation that would be expected to increase alcohol drinking, namely following periods of alcohol deprivation. This suggests that prazosin may be effective in reducing alcohol relapse that often occurs during attempts to achieve permanent alcohol abstinence in treatment-seeking alcoholics and heavy drinkers.

Terazosin for the treatment of trauma-related nightmares: a report of 4 cases

The selective α1-adrenergic antagonist prazosin has been shown in multiple studies to be effective in targeting trauma-related nightmares in posttraumatic stress disorder. There are limited data regarding the effectiveness of another selective α1-adrenergic antagonist terazosin for the treatment of trauma-related nightmares. We present 4 cases in which terazosin was effectively used to treat nightmares as a second-line agent after prazosin failure. Further studies are needed to validate terazosin as an alternative to prazosin for the treatment of posttraumatic stress disorder-related nightmares.

Prazosin reduces alcohol drinking throughout prolonged treatment and blocks the initiation of drinking in rats selectively bred for high alcohol intake

BACKGROUND

This study examined whether prazosin reduces alcohol drinking over the course of prolonged treatment and whether it blocks the initiation of alcohol drinking in rats with a genetic predisposition toward high alcohol drinking, that is alcohol-preferring (P) rats.

METHODS

In study one, alcohol-experienced P rats that had been drinking alcohol for 2 h/d for several months were treated daily with prazosin (0, 0.5, 1.0, or 2.0 mg/kg body weight [BW]) for 7 weeks. In study two, alcohol-naïve P rats were treated daily with prazosin (0, 1.0, or 2.0 mg/kg BW) for 2 weeks prior to, or concomitantly with, the initiation of alcohol access and throughout 3 weeks of alcohol availability. Prazosin treatment and alcohol access were then discontinued for 2 weeks followed by reinstatement of alcohol access without prazosin treatment for 4 weeks, followed by resumption of daily prazosin treatment (2.0 mg/kg BW) for 3 weeks.

RESULTS

Prazosin reduced alcohol drinking throughout 7 weeks of treatment in P rats accustomed to drinking alcohol. Following termination of prazosin treatment, alcohol drinking slowly returned to pretreatment baseline. Reduced alcohol intake was accompanied by increased water intake. In alcohol-naïve P rats, prazosin administration prior to the first opportunity to drink alcohol and throughout 3 weeks of alcohol access retarded acquisition of alcohol drinking and reduced the amount of alcohol consumed. When prazosin was administered concomitantly with the first opportunity to drink alcohol, it abolished acquisition of alcohol drinking. Discontinuation of prazosin treatment allowed expression of a genetic predisposition toward high alcohol drinking to gradually emerge. Prazosin retained the ability to reduce alcohol intake with repeated treatments.

CONCLUSIONS

Prazosin decreased alcohol drinking during prolonged treatment and may be useful for treating alcoholism and alcohol-use disorders. Prazosin may also be useful for deterring the initiation of drinking in individuals with a family history of alcoholism.

Identification and profiling of novel α1A-adrenoceptor-CXC chemokine receptor 2 heteromer

We have provided the first evidence for specific heteromerization between the α(1A)-adrenoceptor (α(1A)AR) and CXC chemokine receptor 2 (CXCR2) in live cells. α(1A)AR and CXCR2 are both expressed in areas such as the stromal smooth muscle layer of the prostate. By utilizing the G protein-coupled receptor (GPCR) heteromer identification technology on the live cell-based bioluminescence resonance energy transfer (BRET) assay platform, our studies in human embryonic kidney 293 cells have identified norepinephrine-dependent β-arrestin recruitment that was in turn dependent upon co-expression of α(1A)AR with CXCR2. These findings have been supported by co-localization observed using confocal microscopy. This norepinephrine-dependent β-arrestin recruitment was inhibited not only by the α(1)AR antagonist Terazosin but also by the CXCR2-specific allosteric inverse agonist SB265610. Furthermore, Labetalol, which is marketed for hypertension as a nonselective β-adrenoceptor antagonist with α(1)AR antagonist properties, was identified as a heteromer-specific-biased agonist exhibiting partial agonism for inositol phosphate production but essentially full agonism for β-arrestin recruitment at the α(1A)AR-CXCR2 heteromer. Finally, bioluminescence resonance energy transfer studies with both receptors tagged suggest that α(1A)AR-CXCR2 heteromerization occurs constitutively and is not modulated by ligand. These findings support the concept of GPCR heteromer complexes exhibiting distinct pharmacology, thereby providing additional mechanisms through which GPCRs can potentially achieve their diverse biological functions. This has important implications for the use and future development of pharmaceuticals targeting these receptors.

Phosphodiesterase (PDE) inhibitors in the treatment of lower urinary tract dysfunction

Several disorders of the human upper and lower urinary tract, such as urinary stone disease, lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia (BPH) and detrusor overactivity, can be therapeutically addressed by influencing the function of the smooth musculature of the ureter, prostate or urinary bladder, respectively. In order to ensure a drug effect without significant adverse events, a certain degree of tissue selectivity is mandatory. The treatment of said conditions aims to focus on orally available drugs acting via intracellular signalling pathways. Specifically, the cyclic nucleotide monophosphate cyclic GMP represents an important mediator in the control of the outflow region (bladder, urethra). The use of phosphodiesterase (PDE) inhibitors, such as sildenafil, tadalafil, vardenafil, avanafil or udenafil, known to restrain the degradation of the second messenger cyclic GMP, offers great opportunities in the treatment of lower urinary tract dysfunction. PDE inhibitors are regarded as efficacious, have a rapid onset of action and favourable effect-to-side-effect ratio. The role of PDE5 inhibitors in the treatment of BPH/LUTS and the overactive bladder has already been addressed in randomized, double-blind, placebo-controlled trials, as well as preliminary open-label studies enrolling either several hundreds or only 20 patients. The purpose of this review is to focus on the potential use and clinical significance of PDE inhibitors in the treatment of storage and voiding dysfunctions of the lower urinary tract. The strategy of modulating the activity of PDE isoenzymes might represent a novel approach in patients with lower urinary tract dysfunction (LUTD).

Molecular modulation of prefrontal cortex: rational development of treatments for psychiatric disorders

Dysfunction of the prefrontal cortex (PFC) is a central feature of many psychiatric disorders, such as attention deficit hyperactivity disorder (ADHD), posttraumatic stress disorder (PTSD), schizophrenia, and bipolar disorder. Thus, understanding molecular influences on PFC function through basic research in animals is essential to rational drug development. In this review, we discuss the molecular signaling events initiated by norepinephrine and dopamine that strengthen working memory function mediated by the dorsolateral PFC under optimal conditions, and weaken working memory function during uncontrollable stress. We also discuss how these intracellular mechanisms can be compromised in psychiatric disorders, and how novel treatments based on these findings may restore a molecular environment conducive to PFC regulation of behavior, thought and emotion. Examples of successful translation from animals to humans include guanfacine for the treatment of ADHD and related PFC disorders, and prazosin for the treatment of PTSD.

Cyclic nucleotide metabolism including nitric oxide and phosphodiesterase-related targets in the lower urinary tract

The clinical data on the use of the orally active phosphodiesterase (PDE) type 5 inhibitors sildenafil (VIAGRA™), vardenafil (LEVITRA™), and tadalafil (CIALIS™) for the treatment of male erectile dysfunction have boosted research activities on the physiology and pharmacology of the organs of the lower urinary tract (LUT). This includes both intracellular signal transduction in the prostate, urinary bladder (detrusor), and urethra, as well as central brain and spinal cord pathways controlling the function of the LUT. Such efforts provided the basis for the development of new therapeutic modalities into the management of dysfunctions/ syndromes of the LUT, some of which are already offered to the patients. The pharmacological treatment of the overactive bladder and the so-called benign prostatic syndrome, including LUT symptomatology and bladder outlet obstruction secondary to benign prostatic enlargement, has primarily focused on selective, orally available drugs acting by influencing intracellular regulatory mechanisms. These agents are regarded efficacious, have a fast onset of drug action in the target tissue and an improved effect-to-side-effect ratio. Better understanding of the functional significance of proteins related to cyclic nucleotide-dependent pathways, such as nitric oxide synthase, cytosolic and membrane-bound guanylyl cyclases, PDE isoenzymes and cyclic AMP- and cyclic GMP-binding protein kinases, the relative distribution in tissues of the LUT, and the consequences for urogenital function, seems to be of particular interest in order to identify new or more selective pharmacological approaches to manage disorders of the LUT. The present review focuses on cyclic nucleotide-related targets involved in the control of the function of the bladder, prostate, and urethra and the significance of those proteins in the process of evolving new pharmacological options for the treatment of LUT symptoms secondary to benign prostatic hyperplasia as well as dysfunctions of the storage and voiding capability of the urinary bladder.

Treatment of erectile dysfunction and lower urinary tract symptoms by phosphodiesterase inhibitors

To date, it is widely accepted that several disorders of the male and female urogenital tract, such as erectile dysfunction, bladder overactivity, urinary stone disease, the benign prostatic syndrome, as well as symptoms of female sexual arousal and orgasmic dysfunctions, can be therapeutically approached by influencing the function of the smooth musculature of the respective organs. To achieve a pronounced drug effect without significant adverse events, a certain degree of tissue selectivity is mandatory. Selective intervention in intracellular pathways regulating smooth muscle tone has become the most promising strategy to modulate tissue and organ function. Since the concept of taking a pill to relieve symptoms of lower urinary tract dysfunction is now widely accepted following the successes of phosphodiesterase 5 (PDE5) inhibitor treatment of erectile dysfunction, the treatment of urological diseases has focused on orally available drugs acting via influencing intracellular signaling pathways, thereby combining a high response rate with the advantage of an on-demand intake. Specifically, the use of isoenzyme-selective PDE inhibitors offers great opportunities in the medical treatment of various genitourinary diseases. These agents are regarded to be safe and to be efficacious, i.e., having a fast onset of drug action and an improved effect-to-side-effect ratio. As experience with this class of compounds and their use in urology is rapidly growing, basic and clinical research in this field will most likely expand the pharmacological armamentarium of innovative treatment options in the next few years. The purpose of this review is to summarize current, as well as potential, upcoming indications for the use of PDE inhibitors in the pharmacotherapy of male erectile dysfunction and lower urinary tract symptoms.

Expression and function of G-protein-coupled receptorsin the male reproductive tract

This review focuses on the expression and function of muscarinic acetylcholine receptors (mAChRs), α1-adrenoceptors and relaxin receptors in the male reproductive tract. The localization and differential expression of mAChR and α1-adrenoceptor subtypes in specific compartments of the efferent ductules, epididymis, vas deferens, seminal vesicle and prostate of various species indicate a role for these receptors in the modulation of luminal fluid composition and smooth muscle contraction, including effects on male fertility. Furthermore, the activation of mAChRs induces transactivation of the epidermal growth factor receptor (EGFR) and the Sertoli cell proliferation. The relaxin receptors are present in the testis, RXFP1 in elongated spermatids and Sertoli cells from rat, and RXFP2 in Leydig and germ cells from rat and human, suggesting a role for these receptors in the spermatogenic process. The localization of both receptors in the apical portion of epithelial cells and smooth muscle layers of the vas deferens suggests an involvement of these receptors in the contraction and regulation of secretion.

Erectile dysfunction and lower urinary tract

During the last decades it turned out that the NO/cGMP signaling cascade is one of the most prominent regulators of a variety of physiological and pathophysiological processes in a broad range of mammalian tissues. Thus cGMP is a key second messenger and targeting this pathway by increasing intracellular cGMP levels is a very successful approach in pharmacology as shown for nitrates, PDE5 inhibitors and more recently for stimulators of the guanylate cyclase. Besides the beneficial effects of cGMP elevation in cardiac, vascular, pulmonary, renal or liver disorders the launch of PDE5 inhibitors for the treatment of erectile dysfunction 10 years ago, has directed a lot of attention to the NO/cGMP signaling in the lower urinary tract. Triggered by the use of PDE5 inhibitors in ED it turned out that cGMP is a common regulatory mechanism for lower urinary tract function also beyond ED. In recent years intense research and development efforts were undertaken to elucidate the role of the NO/cGMP and to fully exploit the therapeutic implications of cGMP elevation in urological disorders in ED and beyond. Therefore we have summarized the effects of cGMP elevation for treatment of erectile dysfunction in males and in females. We have also reviewed the recent pre-clinical and clinical lines of evidence for treatment options of benign prostatic hyperplasia and lower urinary tract symptoms in male patients and overactive bladder and urinary incontinence in female patients. In addition we also touch more speculative concepts using cGMP elevating drugs for the treatment of premature ejaculation, peyornies disease and stone disease.

A pilot trial of the alpha-1 adrenergic antagonist, prazosin, for alcohol dependence

BACKGROUND

Current medications for alcohol dependence (AD) show only modest efficacy. None target brain noradrenergic pathways. Theory and preclinical evidence suggest that noradrenergic circuits may be involved in alcohol reinforcement and relapse. We therefore tested the alpha-1 adrenergic receptor antagonist, prazosin, as a pharmacotherapy for AD.

METHODS

We randomized 24 participants with AD but without posttraumatic stress disorder to receive either prazosin or placebo in a 6-week, double-blind pilot study. Medication was titrated to a target dose of 4 mg QAM, 4 mg QPM, and 8 mg QHS by the end of week 2. Participants received 5 medical management treatment sessions. Participants were reminded 3 times each day via a text pager to take medications and to call a telephone monitoring system once daily to provide self-reports of alcohol consumption and craving, the primary outcome measures. Results were analyzed using mixed linear regression adjusted for drinking days per week at baseline and week number.

RESULTS

Twenty of the 24 (83%) subjects completed. Among the completers, the prazosin group reported fewer drinking days per week than the placebo group during the final 3 weeks of the study. Since only 1 woman was randomized to placebo and only three women completed the trial, the following results focus on the 17 male completers. The prazosin group reported fewer drinking days per week and fewer drinks per week during the final 3 weeks of the study; average total number of drinking days for the placebo group 5.7 (SEM 1.9) versus 0.9 (SEM 0.5) for the prazosin group, and average total number of drinks 20.8 (SEM 6.5) for the placebo group versus 2.6 (SEM 1.3) for the prazosin group. Rates of adverse events were equivalent across conditions.

CONCLUSIONS

Prazosin holds promise as a pharmacologic treatment for AD and deserves further evaluation in a larger controlled trial.

Nonnightmare distressed awakenings in veterans with posttraumatic stress disorder: response to prazosin

Twenty-two veterans with posttraumatic stress disorder (PTSD) were assessed for trauma-related nightmares and nonnightmare distressed awakenings (NNDA) before and after treatment with the alpha-1 adrenoreceptor antagonist prazosin at an average bedtime dose of 9.6 mg/day. Ratings combining frequency and intensity dimensions of trauma-related nightmares decreased from 3.6 to 2.2, NNDA from 5.2 to 2.1, and sleep difficulty from 7.2 to 4.1 per week. These results suggest that increased brain adrenergic activity may contribute to the pathophysiology of both trauma-related nightmares and NNDA in PTSD.

Uroflowmetric assessment of acute effects of sildenafil on the voiding of men with erectile dysfunction and symptomatic benign prostatic hyperplasia

PURPOSE

To evaluate the acute effects of sildenafil (50 mg) on the micturation of men with erectile dysfunction (ED) and concomitant benign prostatic hyperplasia (BPH) with lower urinary tract symptoms (LUTS) using uroflowmetric parameters.

MATERIALS AND METHODS

A total of 68 male patients randomized into two groups (36 treatment, 32 control groups) with International Prostate Symptom Score (IPSS) greater than 7 and International Index of Erectile Dysfunction-erectile function domain score lower than 26 were enrolled in the study. Patients in the treatment group received a single dose of 50 mg of oral sildenafil. Patients in the control group received no treatment. Prevoiding urine volumes determined ultrasonographically and voided urine volumes were also recorded. Statistical comparisons were made with the use of analysis of variance (ANOVA).

RESULTS

Mean ages were similar between treatment and control groups (60.4 +/- 9.8 and 58.6 +/- 8.3 years, respectively, P = 0.430). In the treatment group the maximum and average flow rates increased significantly (Q (max) from 15.6 +/- 6.8 cc/s to 19.3 +/- 7.2 cc/s, P < 0.0001; Q (avg) from 7.3 +/- 3.0 cc/s to 9.1 +/- 3.0 cc/s, P < 0.0001) with sildenafil administration, while other parameters studied remained unchanged.

CONCLUSION

Despite the limitations of variations of uroflowmetry, this study showed that sildenafil improves Q (max) and Q (avg) in patients suffering from ED with concomitant BPH-LUTS. Long-term studies are needed to evaluate the effects on IPSS, side effects, and drug interactions.

Effects of phosphodiesterase inhibitors on tension induced by norepinephrine and accumulation of cyclic nucleotides in isolated human prostatic tissue

OBJECTIVES

To further evaluate the mechanism of action of phosphodiesterase (PDE) inhibitors on the human prostate, the effects of PDE4 and PDE5 inhibitors on the tension induced by norepinephrine (NE) and on the intracellular levels of cyclic nucleotides in isolated human prostatic tissue were investigated.

METHODS

Using the organ bath technique, the effects of increasing concentrations (1 nM to 10 microM) of the PDE5 inhibitors sildenafil, tadalafil, and vardenafil and the PDE4 inhibitors rolipram and RP 73401 on the tension induced by NE (40 microM) of prostate strip preparations were investigated. The accumulation of cyclic guanosine monophosphate and cyclic adenosine monophosphate in response to drug exposure was determined by radioimmunoassays.

RESULTS

The tension induced by NE was dose dependently reversed by the drugs with the following rank order of efficacy: tadalafil greater than RP 73401 greater than rolipram greater than or equal to vardenafil greater than sildenafil. The maximal reversion of tension values ranged from 52.3% (tadalafil) to 17% (sildenafil). Of the PDE inhibitors, only tadalafil induced a 50% reversion of the initial tension. The most prominent enhancement in tissue cyclic adenosine monophosphate was registered in response to RP 73401 (11-fold), and cyclic guanosine monophosphate levels were significantly elevated by tadalafil, vardenafil, and sildenafil (28-fold, 12-fold, and 3-fold, respectively).

CONCLUSIONS

Our results have demonstrated that drugs interfering with the cyclic nucleotide-mediated pathways can reverse the tension induced by NE in isolated prostatic tissue and elevate cyclic adenosine monophosphate and cyclic guanosine monophosphate. Our findings serve to explain how PDE inhibitors can affect symptoms of lower urinary tract symptoms and benign prostatic hyperplasia.

Immunolocalization of alpha(1A)-adrenoceptors in rat and human epididymis

Immunohistochemistry was conducted to analyze the cellular localization of alpha(1A)-adrenoceptors along rat and human epididymis. ADR-A, a polyclonal antibody that recognizes the specific C-terminal region of alpha(1A)-adrenoceptors, immunostained this adrenoceptor subtype in smooth muscle cells surrounding the epididymal tubules and interstitial blood vessels and in subpopulations of epithelial cells from adult rat and human caput and cauda epididymidis. The same cell types from rat epididymidis were immunostained by ADR-1, a polyclonal antibody that recognizes a common region of the three alpha(1)-adrenoceptor subtypes, alpha(1A), alpha(1B), and alpha(1D). Immunostaining with both antibodies was also conducted in adult rat and human vas deferens and seminal vesicle used as positive controls because of the abundance of alpha(1A)-adrenoceptors in these tissues. ADR-A- and ADR-1-positive immunostaining was differentially distributed depending on the antibody, method of tissue fixation (Bouin-fixed and fresh frozen tissues), species (rat and human), tissue (caput and cauda epididymidis), and age (immature and adult rats) analyzed. This is the first report immunolocalizing alpha(1A)-adrenoceptor along rat and human epididymis. The presence of this adrenoceptor subtype in epididymal smooth muscle and epithelial cells indicates their contribution to smooth muscle contractile responses and a possible role in the absorptive and/or secretory activities of the epithelium lining the epididymal duct. Taken together, our results should contribute to a better understanding of the physiological role of alpha(1)-adrenoceptors in the epididymidis and the importance of the sympathetic nervous system for male (in)fertility.

K+ channel modulation of slow wave activity in the guinea-pig prostate

BACKGROUND AND PURPOSE

The aim of this study was to investigate the role of different K(+) channel populations and the inhibitory effect of various exogenously applied K(+) channel openers in the regulation of slow wave activity in the guinea-pig prostate.

EXPERIMENTAL APPROACH

Recordings of membrane potential were made using intracellular microelectrodes.

KEY RESULTS

Tetraethylammonium (TEA 300 micro M and 1 mM), iberiotoxin (150 nM) and 4-aminopyridine (4-AP 1 mM) increased the frequency of slow wave discharge. Apamin (1-200 nM) and glibenclamide (1 micro M) had no effect on slow wave activity. Lemakalim (1 micro M) and PCO-400 (1 micro M) abolished the slow waves, as did sodium nitroprusside (SNP 10 micro M) and calcitonin gene-related peptide (CGRP 100 nM). The inhibitory effect of these agents was independent of a significant change in membrane potential. In the presence of 4-AP (1 mM), TEA (1 mM) or glibenclamide (1 micro M) the inhibitory actions of SNP (10 micro M) were attenuated. The inhibitory actions of CGRP (100 nM) were also reversed by glibenclamide (1 micro M). In contrast, isoprenaline (1 micro M) did not alter the frequency of slow wave discharge.

CONCLUSIONS AND IMPLICATIONS

These results demonstrate that BK(Ca) and 4-AP-sensitive K(+) channels regulate the frequency of prostatic slow wave discharge. SNP and CGRP abolish slow waves in a hyperpolarisation-independent manner, partially via opening of K(ATP) channels. BK(Ca) and 4-AP-sensitive K(+) channels also play an important role in the SNP-induced inhibition of slow wave activity. The lack of membrane hyperpolarisation associated with the SNP- and CGRP-induced inhibition implies that the channels involved in this action are not predominantly located on the smooth muscle cells.

A parallel group placebo controlled study of prazosin for trauma nightmares and sleep disturbance in combat veterans with post-traumatic stress disorder

BACKGROUND

Excessive brain responsiveness to norepinephrine appears to contribute to post-traumatic stress disorder (PTSD), particularly at night. Prazosin, a brain active alpha-1 adrenergic receptor antagonist, significantly reduced trauma nightmares and sleep disturbance in 10 Vietnam War combat veterans in a previous placebo-controlled crossover study. The current parallel group trial in a larger sample of veterans evaluated prazosin effects on trauma nightmares, sleep quality, global clinical status, dream characteristics, and comorbid depression.

METHODS

Forty veterans (mean age 56 +/- 9) with chronic PTSD and distressing trauma nightmares and sleep disturbance were randomized to evening prazosin (13.3 +/- 3 mg/day) or placebo for 8 weeks.

RESULTS

In the evaluable sample (n = 34), primary outcome measures demonstrated that prazosin was significantly superior to placebo for reducing trauma nightmares and improving sleep quality and global clinical status with large effect sizes. Prazosin shifted dream characteristics from those typical of trauma-related nightmares toward those typical of normal dreams. Blood pressure changes from baseline to end study did not differ significantly between prazosin and placebo.

CONCLUSIONS

Prazosin is an effective and well-tolerated treatment for trauma nightmares, sleep disturbance and global clinical status in veterans with chronic PTSD.

“Phenotypic” pharmacology: The influence of cellular environment on G protein-coupled receptor antagonist and inverse agonist pharmacology

A central dogma of G protein-coupled receptor (GPCR) pharmacology has been the concept that unlike agonists, antagonist ligands display equivalent affinities for a given receptor, regardless of the cellular environment in which the affinity is assayed. Indeed, the widespread use of antagonist pharmacology in the classification of receptor expression profiles in vivo has relied upon this 'antagonist assumption'. However, emerging evidence suggests that the same gene-product may exhibit different antagonist pharmacological profiles, depending upon the cellular context in which it is expressed-so-called 'phenotypic' profiles. In this commentary, we review the evidence relating to some specific examples, focusing on adrenergic and muscarinic acetylcholine receptor systems, where GPCR antagonist/inverse agonist pharmacology has been demonstrated to be cell- or tissue-dependent, before going on to examine some of the ways in which the cellular environment might modulate receptor pharmacology. In the majority of cases, the cellular factors responsible for generating phenotypic profiles are unknown, but there is substantial evidence that factors, including post-transcriptional modifications, receptor oligomerization and constitutive receptor activity, can influence GPCR pharmacology and these concepts are discussed in relation to antagonist phenotypic profiles. A better molecular understanding of the impact of cell background on GPCR antagonist pharmacology is likely to provide previously unrealized opportunities to achieve greater specificity in new drug discovery candidates.

Alfuzosin: an alpha1-receptor blocker for the treatment of lower urinary tract symptoms associated with benign prostatic hyperplasia

Alpha1-receptor blockers have become first-line therapy for the medical management of lower urinary tract symptoms associated with benign prostatic hyperplasia. However, adverse effects such as cardiovascular intolerance can limit their use. This article focuses on alfuzosin, a clinically uroselective, alpha1-adrenergic antagonist that is available as a novel once-daily formulation that does not require dose titration. Alfuzosin is less vasoactive than other non-subtype selective alpha1-receptor blockers. In addition to effects on lower urinary tract symptoms, it is also used as an adjunct to urethral catheterisation in patients with acute urinary retention related to benign prostatic hyperplasia, and can improve sexual function and health-related quality of life in benign prostatic hyperplasia sufferers.

Spontaneous electrical activity in the prostate gland

The cellular mechanisms that underlie the initiation, maintenance and propagation of electrical activity in the prostate gland remain little understood. Intracellular microelectrode recordings have identified at least two distinct electrical waveforms: pacemaker potentials and slow wave activity. By analogy with the intestine, we have proposed that pacemaker activity arises from a morphologically distinct group of c-Kit positive interstitial cells that lie mainly between the glandular epithelium and smooth muscle layers. We speculate that pacemaker activity arising from the prostatic interstitial cells (PICs) is likely to propagate and initiate slow wave activity in the smooth muscle cells resulting in contraction of the stromal smooth muscle wall. While spontaneous electrical activity in the prostate gland is myogenic in origin, it is clear that nerve-mediated agents are able to modulate this activity. Excitatory agents such as histamine, phenylephrine and a raised potassium saline all increase slow wave discharge. In contrast, nitric oxide donors reduce or abolish the spontaneous electrical events. However, the cellular mechanisms underlying the action of various endogenously released agents remain to be elucidated.

In vitro functional responses of isolated normal human prostatic tissue to compounds interacting with the cyclic guanosine monophosphate pathway

OBJECTIVES

To examine the effects of some nitric oxide-donating agents, as well as the C-type natriuretic peptide (CNP), on isolated human prostatic tissue. To date, guanylyl cyclases and cyclic guanosine monophosphate (cGMP)-degrading phosphodiesterases represent important target proteins for the development of new drugs for the treatment of lower urinary tract symptoms and benign prostatic hyperplasia.

METHODS

Using the organ bath technique, the effects of sodium nitroprusside, S-nitrosoglutathione, S-nitrosocysteine, linsidomine, and CNP (1 nM to 1.0/10 microM) on the tension induced by norepinephrine of prostatic tissue strips were investigated. The tissue was also exposed to three different concentrations of the drugs, and the production of cGMP and cyclic adenosine monophosphate (cAMP) was determined.

RESULTS

The tension induced by 40 microM norepinephrine of the isolated prostatic tissue was dose dependently reversed by the drugs. The rank order of potency was sodium nitroprusside more than S-nitrosoglutathione more than linsidomine more than S-nitrosocysteine, which was equal to CNP (1 microM). The reversal of tension induced by the greatest drug concentrations ranged from 50% relaxation with sodium nitroprusside to 42% relaxation with CNP. The relaxing effects of the drugs were paralleled by a 2-fold to 40-fold and 2-fold to 45-fold increase in tissue levels of cAMP and cGMP, respectively.

CONCLUSIONS

Our results provide further evidence that cGMP and cAMP are involved in the control of the normal function of human prostatic smooth muscle. Our findings may provide new strategies for future therapeutics used in the treatment of lower urinary tract symptoms and bladder outlet obstruction secondary to benign prostatic hyperplasia.

Immunohistochemical Distribution of cAMP- and cGMP-Phosphodiesterase (PDE) Isoenzymes in the Human Prostate

OBJECTIVES

With the introduction of sildenafil citrate (Viagra), the concept of phosphodiesterase (PDE) inhibition has gained tremendous interest in the field of urology. Cyclic nucleotide second messengers cGMP and cAMP have been assumed to be involved in the control of the normal function of the prostate. The aim of the present study was to evaluate by means of immunohistochemistry the expression and distribution of some cAMP- and cGMP-PDE isoenzymes in the prostate.

MATERIAL & METHODS

Cryostat sections (10 microM) of formaldehyde-fixated tissue segments excised from the transition zone of human prostates were incubated with primary antibodies directed against the PDE isoenzymes 3, 4, 5, and 11. Then, sections were exposed to either fluorescein isothiocyanate- (FITC) or Texas Red- (TR) labeled secondary antibodies and visualization was commenced by means of laser fluorescence microscopy.

RESULTS

TR-immunofluorescence indicating the presence of PDE4 (cAMP-PDE) was abundantly observed in the fibromuscular stroma as well as in glandular structures of the transition zone. In contrast to the distribution of PDE4, immunoactivity indicating PDE5 (cGMP-PDE) and 11 (dual substrate PDE) was mainly observed in glandular and subglandular areas. No immunostaining for PDE3 (cGMP-inhibited PDE) was detected.

CONCLUSION

Our results confirm the presence of PDE isoenzymes 4, 5 and 11 in the transition zone of the human prostate and present evidence that these isoenzymes are not evenly distributed. These findings are in support of the hypothesis that there might be a rationale for the use of PDE inhibitors in the pharmacotherapy of BPH and LUTS.

Effect of D-004, a lipid extract from the Cuban royal palm fruit, on in vitro and in vivo effects mediated by alpha-adrenoceptors in rats

BACKGROUND

Benign prostatic hyperplasia (BPH) is the non-malignant, uncontrolled growth of glandular and stromal elements of the prostate gland. Lipid extracts from Saw palmetto (Arecaceae) fruits are widely used to treat BPH. The Cuban royal palm (Roystonea regia) is a member of the same family. Previous studies have found that D-004, a lipid extract from the R. regia fruit, administered orally at 200-800 mg/day for 14 days, prevented testosterone- but not dihydrotestosterone-induced prostate hyperplasia in rats.

OBJECTIVE

To determine whether D-004 can inhibit noradrenaline (NA) [norepinephrine]- and acetylcholine (ACh)-induced smooth muscle contraction in rat vas deferens and to investigate the in vivo effects of D-004 on NA pressure-elevating effects in rats, an effect mediated by vascular alpha1-adrenoceptors.

METHODS

In vitro effects were investigated by adding D-004 (125-500 microg/mL) to preparations of rat vas deferens suspended in an organ bath containing Tyrode's solution, in which in vitro contractions were induced by NA or ACh. Negative and positive controls containing Tyrode's solution alone or with Saw palmetto extracts (125-500 microg/mL), respectively, were included. To assess the in vivo effects of D-004 on arterial blood pressure, rats were randomly distributed to one of five groups (ten rats/group): these consisted of a negative control group receiving the vehicle, two groups treated with D-004 (400 and 800 mg/kg) and two other groups treated with Saw palmetto (400 and 800 mg/kg). All treatments were orally administered. Rats were anaesthetised with sodium thiopental. Heart rate and blood pressure were registered in baseline conditions. Immediately afterwards, rats were injected intravenously over 5 seconds with successive doses of NA (1, 2 and 4 microg/kg) [0.1mL/100g], with 5 minutes' interval between doses.

RESULTS

D-004 and Saw palmetto (125-500 microg/mL) significantly (p < 0.05) and dose dependently inhibited contractions induced by NA in rat vas deferens versus control. D-004 was more effective in inhibiting NA-induced contractions than Saw palmetto. The contractions induced by NA in preparations with D-004 (500 microg/mL) were weaker (p < 0.05) than in preparations containing Saw palmetto (500 microg/mL). At 125 microg/mL, D-004 inhibited the contractions induced by NA 1 and 32 x 10(-6) mol/L by 70.8% and 28.5%, respectively, and Saw palmetto by 56.2% and 10.7%, respectively. At 500 microg/mL, D-004 inhibited these contractions by 100.0% and 71.3%, and Saw palmetto by 80.0% and 42.7%, respectively. The inhibitory concentrations of 50% (IC50) for NA contractions were 148.34 (D-004) and 188.38 (Saw palmetto) microg/mL. D-004 and Saw palmetto significantly (p < 0.05) and to a similar extent inhibited ACh-induced contractions, but less effectively than contractions induced by NA, since at 125 microg/mL they were ineffective. At a dose of 800 mg/kg, but not at 400 mg/kg, D-004 and Saw palmetto inhibited the pressure-elevating effects induced with low (1 microg/kg) but not with high doses (2 and 4 microg/kg) of NA.

CONCLUSIONS

D-004 and Saw palmetto extracts inhibited in vitro the contractile responses to NA and ACh in rat vas deferens, and were more effective in inhibiting NA than ACh contractions. The in vivo effects of D-004 and Saw palmetto on the hypertensive response induced by NA were significant but modest. These results are preliminary as the relevance of the effects of D-004 on alpha1-adrenoceptors deserves further investigation, including comparative studies versus specific defined alpha1-adrenoceptor antagonists.

Synthesis and development of new 2-substituted 1-[3-(4-arylpiperazin-1-yl)propyl]-pyrrolidin-2-one derivatives with antiarrhythmic, hypotensive, and α-adrenolytic activity

A series of new 1-[3-(4-arylpiperazinyl-1-yl)-2-(N-alkylcarbamoyloxy)propyl]-pyrrolidin-2-one derivatives (4a-12a) were synthesised and tested for their electrocardiographic, antiarrhythmic and antihypertensive activity, as well as for the alpha1- and alpha2-adrenoceptor binding affinities. Of the newly synthesised derivatives, 1-{2-(N-2-methylethylcarbamoiloxy)-3-[4-(2-methoxyphenyl)piperazin-1-yl)]propyl}pyrrolidin-2-one dihydrochloride (10a) was the most active in prophylactic antiarrhythmic tests, its ED50 value equalling 2.7 mg kg(-1), and the therapeutic index being 75.2; moreover, compound 10a was also found to possess hypotensive activity. A preliminary molecular modelling study suggested that the selected alpha1-AR antagonist distances and angles between pharmacophoric features, estimated for the tested compounds, were in good agreement with the parameters evaluated for ligands.

Alpha-adrenoreceptor blockade with phenoxybenzamine does not affect the ability of the nose to condition air

The primary function of the nose is to warm and humidify air. We have previously shown that raising nasal mucosal temperature by immersing feet in warm water increases the amount of water evaporated by the nose as air passes through it (nasal conditioning capacity; Abbott D, Baroody F, Naureckas E, and Naclerio R. Am J Rhinol 15: 41-45, 2001). To investigate further the effect of nasal mucosal temperature on nasal conditioning capacity, we raised the temperature through alpha-adrenoreceptor blockade by intranasally administering phenoxybenzamine. We hypothesized that blocking alpha-adrenoreceptors during inhalation of cold, dry air would lead to an increase in nasal blood flow, surface temperature, and nasal conditioning capacity, as measured by the water gradient. After appropriate pilot studies, we performed a double-blind, placebo-controlled, two-way crossover study in nine nonatopic, healthy subjects by studying the effect of treatment with intranasal phenoxybenzamine. Nasal mucosal temperature increased significantly after administration of phenoxybenzamine and was associated with a significantly smaller net decrease in nasal mucosal temperature after exposure to cold, dry air (P < 0.05). However, there were no significant differences in nasal conditioning capacity between treatments (P > 0.05). Phenoxybenzamine decreased the symptom of rhinorrhea after exposure to cold, dry air (P < 0.05), but congestion was not different between individuals given phenoxybenzamine and placebo (P > 0.05). Our data demonstrate that phenoxybenzamine, despite raising mucosal temperature and not affecting nasal volume, did not affect the ability of the nose to warm and humidify air.

Recent advances in the identification of a 1- and a 2-adrenoceptor subtypes: therapeutic implications

The cloning of multiple subtypes of both alpha1- and alpha2-adrenoceptors has renewed interest in the therapeutic application of agents interacting with these receptors. Effort has primarily been directed towards the design of uroselective alpha1-adrenoceptor antagonists for the treatment of benign prostatic hyperplasia (BPH). Evidence is accumulating for the involvement of a novel alpha1-adrenoceptor, designated as alpha1L-adrenoceptor, in alpha1-adrenoceptor-mediated smooth muscle contraction in prostatic and other urogenital tissues. While several antagonists showing a high degree of uroselectivity in animal models have been identified, their clinical superiority over the currently available alpha1-adrenoceptor antagonists has not yet been demonstrated. It is possible that the interaction with alpha1-adrenoceptors, as yet uncharacterised subtypes, at non-prostatic sites contributes to the therapeutic activity of this drug class in BPH. The alpha1-adrenoceptor subtypes involved in the control of vascular tone are currently being evaluated, and the profile of interaction with the various alpha1-adrenoceptor subtypes may play a key role in the efficacy of cardiovascular drugs such as carvedilol. Alpha2-adrenoceptor agonists are now being employed for a variety of therapeutic applications, most involving actions on receptors within the central nervous system (CNS). These agents are useful in the treatment of hypertension, glaucoma, opiate withdrawal and attention deficit hyperactivity disorder (ADHD), and as analgesics and adjuncts to general anaesthesia. While subtype selectivity has not yet been applied to the design of new alpha2-adrenoceptor agonists for these applications, recent gene mutation/knock-out experiments have identified the alpha2-subtypes involved in some of these actions, and optimisation of a therapeutic profile may be possible. Furthermore, the design of agents combining affinities for multiple adrenoceptor subtypes, or the combination of a specific adrenoceptor affinity profile with another pharmacological action, may offer advantages over molecules selective for an individual adrenoceptor subtype.

Role of the newer alpha, -adrenergic-receptor antagonistsin the treatment of benign prostatic hyperplasia-related lower urinary tract symptoms

BACKGROUND

Although initially introduced for the management of hypertension, alpha(1)-adrenergic-receptor antagonists (alpha1-blockers) have become the standard of care for the medical management of benign prostatic hyperplasia (BPH)-related lower urinary tract symptoms (LUTS). However, these agents have the potential to produce orthostatic hypotension and other blood pressure-related adverse effects in normotensive patients and in those receiving concurrent treatment with other antihypertensive agents. As a result, more "uroselective," less vasoactive alpha(1)-blockers have been developed.

OBJECTIVE

This article reviews current information on the role of alpha(1)-blockers in the treatment of BPH-related LUTS. The focus is on tamsulosin and alfuzosin, newer "uroselective" agents in this class that have a decreased potential for cardiovascular adverse effects.

METHODS

Relevant articles were identified through a search of the English-language literature indexed on MEDLINE and the proceedings of scientific meetings from 1976 to 2003. The search terms were benign prostatic hyperplasia treatment, alpha(1)-adrenergic-receptor blocker, uroselectivity, lower urinary tract symptoms, complications, and cardiovascular.

RESULTS

Tamsulosin has selectivity for the a alpha(1) and alpha(1d) receptor subtypes. Alfuzosin, although not receptor subtype selective, is clinically "uroselective" and does not significantly affect vascular alpha-adrenergic receptors. Both agents are efficacious in relieving LUTS and have a decreased potential for such cardiovascular adverse effects as postural hypotension. Common adverse events with these agents include dizziness and asthenia.

CONCLUSION

Based on the available data, "uroselective" alpha(1)-blockers should be considered over older, more vasoactive agents for the medical management of LUTS, particularly in patients with BPH and hypertension.

Prazosin reduces trauma-related nightmares in older men with chronic posttraumatic stress disorder

Trauma-related nightmares in posttraumatic stress disorder (PTSD) rarely respond to pharmacologic treatment. Neurobiologic data suggest that enhanced brain responsiveness to adrenergic stimulation may contribute to the pathophysiology of trauma-related nightmares in PTSD. Nine older men with chronic PTSD secondary to military or Holocaust trauma were prescribed the lipophilic alpha-1 adrenergic antagonist prazosin for treatment-resistant trauma-related nightmares. Prazosin 2 mg to 4 mg 1 hour before bedtime substantially reduced nightmares and moderately or markedly reduced overall PTSD severity in 8 of 9 subjects. Prazosin was well tolerated. These open-label results are consistent with demonstrated therapeutic efficacy of prazosin for PTSD nightmares and sleep disturbance in a recent placebo-controlled trial in Vietnam veterans.

Alpha 1-adrenoceptor effects mediated by protein kinase C alpha in human cultured prostatic stromal cells

1 We have investigated the effects of alpha(1)-adrenoceptor stimulation upon contractility, Ca(2+) influx, inositol phosphate production, and protein kinase C (PKC) translocation in human cultured prostatic stromal cells (HCPSC). 2 The alpha(1)-adrenoceptor selective agonist phenylephrine elicited contractile responses of HCPSC, i.e. a maximal cell shortening of 45+/-6% of initial cell length, with an EC(50) of 1.6+/-0.1 microM. The alpha(1)-adrenoceptor selective antagonists prazosin (1 microM) and terazosin (1 microM) both blocked contractions to phenylephrine (10 microM). The L-type calcium channel blocker nifedipine (10 microM), and the PKC inhibitors Gö 6976 (1 microM) and bisindolylmaleimide (1 microM) also inhibited phenylephrine-induced contractions. 3 Phenylephrine caused a concentration dependent increase in inositol phosphate production (EC(50) 119+/-67 nM). This response was blocked by terazosin (1 microM). 4 Phenylephrine caused the translocation of the PKC alpha isoform, but not the beta, delta, gamma, epsilon or lambda isoforms, from the cytosolic to the particulate fraction of HCPSC, with an EC(50) of 5.7+/-0.5 microM. 5 In FURA-2AM (5 microM) loaded cells, phenylephrine elicited concentration dependent increases in [Ca(2+)](i), with an EC(50) of 3.9+/-0.4 microM. The response to phenylephrine (10 microM) was blocked by prazosin (1 microM), bisindolymaleimide (1 microM), and nifedipine (10 microM). 6 In conclusion, this study has shown that HCPSC express functional alpha(1)-adrenoceptors, and that the intracellular pathways responsible for contractility may be largely dependent upon protein kinase C activation and subsequent opening of L-type calcium channels.

Lysophosphatidic acid stimulates proliferation of cultured smooth muscle cells from human BPH tissue: sildenafil and papaverin generate inhibition

BACKGROUND

The endogenous substance lysophosphatidic acid (LPA) has been found to generate proliferation of cultured smooth muscle cells (SMC). Therefore, the effect of LPA on human benign prostate hyperplasia (BPH) could be of interest.

METHODS

The proliferative effect of LPA on cultured human prostatic SMC from specimens obtained at trans-urethral resection of the prostate (TURP) because of BPH, was analyzed by [3H]-thymidine and [35S]-methionine incorporation. In addition, LPA stimulated BPH SMC were treated with papaverin, forskolin, sildenafil or zaprinast, well known to increase the intracellular level of cAMP or cGMP.

RESULTS

LPA produced a dose-dependent increase in BPH SMC, both regarding DNA- and protein-synthesis with EC50 values of 3 and 10 microM, respectively. Furthermore, both papaverin, a general phosphodiesterase inhibitor regarding cAMP hydrolyzes, and forskolin, an adenylyl cyclase stimulating agent, inhibited the LPA-stimulated DNA replication in a dose dependent manner with IC50 = 2.5, and 0.35 microM, respectively. cGMP increasing agents, such as the NO-donors SIN-1 and SNAP, produced a weak anti-proliferative response. However, both phosphodiesterase 5 inhibitors sildenafil (Viagra) and zaprinast efficiently blocked DNA replication. In addition, when the protein synthesis was examined, we found that the LPA response was significantly inhibited by forskolin and papaverin.

CONCLUSIONS

The major conclusion of this investigation is that the endogenous serum component LPA, is able to promote human BPH SMC growth. In addition, our study indicates that cyclic nucleotides can inhibit this effect. Future clinical studies will be needed to determine if different specific phosphodiesterase inhibitors per se or in combination could represent a new therapeutic possibility for the treatment of BPH.

Effect of KMD-3213, an alpha1A-adrenoceptor antagonist, on the prostatic urethral pressure and blood pressure in male decerebrate dogs

BACKGROUND

KMD-3213 is an alpha1A-adrenoceptor-selective antagonist currently being developed for the treatment of urinary outlet obstruction in patients with benign prostatic hyperplasia. In the present study, the uroselectivity of KMD-3213 was evaluated and compared with that of prazosin and tamsulosin in a decerebrate dog model.

METHODS

Intercollicular decerebration was carried out in male mongrel dogs under anesthesia. The inhibitory effects of intravenously and intraduodenally administered compounds on the increase in intraurethral pressure (IUP) induced by electrical stimulation of the hypogastric nerve were estimated. Systemic blood pressure was measured simultaneously.

RESULTS

The alpha1-antagonists tested produced a dose-dependent inhibition of the induced IUP response and decreased mean blood pressure (MBP). The ID50 of KMD-3213, tamsulosin and prazosin for IUP (dose required to inhibit the increase in IUP by 50%) was 3.15, 1.73 and 11.8 microg/kg i.v., respectively, and the ED20 for the hypotensive effect (dose required to reduce MBP by 20%) was 8.03, 0.59 and 2.46 microg/kg i.v., respectively. The data indicate that uroselectivity (ED20/ID50) of KMD-3213 is 12- and 7.5-fold higher than that of prazosin and tamsulosin, respectively. When the drugs were administered intraduodenally, KMD-3213 was sufficiently absorbed from the digestive tract and continued to demonstrate at least 3.8-fold higher uroselectivity than tamsulosin.

CONCLUSION

Based on these findings, KMD-3213 appears to be an effective orally active compound for decreasing urethral resistance during micturition that does not induce any negative cardiovascular effects in patients with benign prostatic hyperplasia.

Role of the 5-HT(2A)receptor and alpha(1)-adrenoceptor in the contractile response of rat pulmonary artery to 5-HT in the presence and absence of nitric oxide

This study investigated the role of 5-HT(2A)receptors and alpha(1)-adrenoceptors in the contractile response to 5-HT in the first branch pulmonary artery of the rat and their interaction with endogenous nitric oxide. 5-HT and phenylephrine induced concentration-dependent contractions. The alpha(1)-adrenoceptor antagonists prazosin, HV723 and phentolamine produced concentration-dependent rightward shifts of the 5-HT concentration-response curves (CRC) consistent with an action at alpha(1)-adrenoceptors. The 5-HT(2)receptor antagonists ritanserin, ketanserin and methysergide produced rightward shifts that were less than would have been predicted for an action solely at 5-HT(2A)receptors. 5-HT and phenylephrine CRCs were shifted to the left by l -NAME. Endothelium denudation also increased the tissue sensitivity to 5-HT. In the presence of l -NAME, ketanserin produced greater antagonism of the 5-HT CRC but not the phenylephrine CRC. Ketanserin also produced greater antagonism of the 5-HT CRC in endothelium denuded rings compared with endothelium intact rings. These findings indicate (a) that both the alpha(1)-adrenoceptor class and the 5-HT(2A)receptor is involved in the contractile response to 5-HT; (b) in the presence of endogenous nitric oxide the contractile response to 5-HT is mediated predominently by alpha(1)-adrenoceptors; (c) inhibition of endogenous nitric oxide potentiates the 5-HT(2A)receptor-mediated component of the contraction.

Alpha 1-adrenergic receptor regulation: basic science and clinical implications

Adrenergic receptors (ARs) are members of the G-protein-coupled receptor family, which includes alpha 1ARs, alpha 2ARs, beta 1ARs, beta 2ARs, beta 3ARs, adenosine, muscarinic, angiotensin, endothelin receptors, and many others that are responsible for a large variety of physiologic effects through G-protein coupling. This review focuses on alpha 1ARs and their regulation at both the mRNA and protein levels. Currently, three alpha 1AR subtypes have been characterized both pharmacologically and at the gene level: alpha 1aAR, alpha 1bAR, and alpha 1dAR. These are expressed in a species- and tissue-dependent manner. Mutagenesis approaches have been extremely valuable in the identification of key residues that govern alpha 1AR ligand binding and signaling. These studies reveal that alpha 1ARs have evolved an exquisitely sensitive regulation of their activity in which any disruption of the native structure has profound effects on subsequent function and effector coupling. Significant advances have also been made in the elucidation of signaling pathway components, resulting in the identification of novel pathways that can lead to pathologic conditions. Specific topics include mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and G-protein-coupled receptor cross-talk pathways. Within this context, recent studies identifying underlying transcriptional mechanisms involved in the regulation of the alpha 1AR subtypes are also discussed. Finally, given the potentially important role of alpha 1ARs in the vasculature, as well as in the pathology of many diseases, such as myocardial hypertrophy and benign prostatic hyperplasia, the clinical relevance of alpha 1AR distribution, pharmacology, and therapeutic intervention is reviewed.

Species differences in the actions of sensory neuropeptides on contractility of the smooth muscle of the rat and guinea-pig prostate

1. The present review describes the actions of sensory neuropeptides on the contractility of the rat and guinea-pig prostate gland and discusses the differences in sensitivity of the smooth muscle of the prostates taken from these species to these neuropeptides. 2. Nerve fibres immunoreactive for the tachykinins substance P and neurokinin A, as well as for the sensory neuropeptide calcitonin gene-related peptide (CGRP), are sparsely distributed throughout the fibromuscular stroma of the prostate gland in both the rat and guinea-pig. 3. In functional experiments, tachykinin agonists potentiate electrical field stimulation-induced contractile responses of prostates taken from guinea-pigs, but have no effect on those taken from rats. This potentiation is through stimulation of tachykinin NK1-receptors. 4. Conversely, CGRP inhibits electrical field stimulation-induced contractile responses of prostates taken from rats, but has no effect on those taken from guinea-pigs. 5. It is concluded that although the sensory innervation to the prostate glands of the rat and guinea-pig appears similar, the nature and sensitivity of the contractile response of the prostatic smooth muscle to applied sensory neuropeptides is vastly different in the two species.

Calcitonin gene-related peptide (CGRP) inhibits contractions of the prostatic stroma of the rat but not the guinea-pig

This study investigated the presence and effects of calcitonin gene-related peptide (CGRP) within the rat and guinea-pig prostate glands. Immunohistochemical studies demonstrated that CGRP immunoreactive nerve fibres are sparsely distributed throughout the prostatic fibromuscular stroma in both species. These CGRP immunopositive nerve fibres shared a similar distribution profile but were not colocalized with tyrosine hydroxylase immunopositive nerve fibres which also innervate the prostatic stroma of these species. Nerve terminals within rat and guinea-pig prostatic tissues were electrically field stimulated (60 V, 0.5 ms, 10 Hz, 20 pulses every 60 s). In guinea-pig preparations, application of human alpha-CGRP, rat adrenomedullin or rat amylin (0.1 nM-1 microM) had no effect on responses to field stimulation. In contrast, both rat and human alpha-CGRP (10 pM-300 nM), rat adrenomedullin (0.3 nM-1 microM) and rat amylin (3 nM-1 microM) concentration-dependently inhibited electrically evoked contractile responses in the rat prostate. The relative order of potency was rat alpha-CGRP=human alpha-CGRP>rat adrenomedullin>rat amylin. The inhibition by rat alpha-CGRP of field stimulation-induced contractions in the rat prostate was competitively antagonized by human CGRP((8-37)) (1, 3 and 10 microM) with a pA(2) of 6.20+/-0.13. Rat alpha-CGRP (10 nM) attenuated contractile responses of the rat prostate to exogenously added noradrenaline (1-100 microM). Inhibitory concentration-response curves to rat alpha-CGRP in rat prostates were unaffected by preincubation in either glibenclamide (10-100 microM), N-nitro-L-arginine methyl ester (L-NAME) (10 microM), bestatin (10 microM), captopril (10 microM) or phosphoramidon (3 microM). Our results indicate that CGRP-induced inhibition of electrically evoked contractions in the rat prostate occurs through activation of postjunctional CGRP(2) receptors which act independently of a K(ATP) channel or nitrergic mechanisms. Degradation of rat alpha-CGRP via peptidases does not appear to occur in the rat prostate.