Pharmacodynamic profiles of different calcium channel blockers

The cardiovascular effects of different calcium channel blockers (CCB), exemplified by nifedipine, verapamil and diltiazem, are not identical. Some of these differences in effect may be due to the different CCBs interacting with different calcium channel subtypes in the tissues, and/or that the drug-receptor sites are separate. The drugs also have different abilities to activate the sympathetic nervous system, nifedipine increasing and diltiazem decreasing the baroreflex sensitivity. Verapamil, but not nifedipine and diltiazem, has a postjunctional alpha-adrenoceptor blocking effect, and can also increase the release of noradrenaline from adrenergic nerves by blocking pre-junctional alpha-adrenoceptors. In addition, verapamil may have a reserpine-like action on sympathetic nerves. The vasodilator actions of CCBs are not uniform, but seem to vary between species, different vascular regions, and different agents. Mechanisms other than blockade of influx of calcium from the extracellular medium have been suggested to explain these differences, including inhibition of intracellular calcium release, blockade of postjunctional alpha-adrenoceptors, interaction with calmodulin, inhibition of cyclic AMP phosphodiesterase, stimulation of Na+-, K+-activated ATPase, stimulation of a calcium pump, and a direct interaction with the contractile proteins. The heterogeneity in pharmacodynamic profile characterizing the CCBs is conspicuous, and may be of importance when selecting agents for the treatment of various cardiovascular and non-cardiovascular disorders.

The role of the alpha-adrenergic receptor in the leg vasoconstrictor response to orthostatic stress

AIM

The prompt increase in peripheral vascular resistance, mediated by sympathetic alpha-adrenergic stimulation, is believed to be the key event in blood pressure control during postural stress. However, despite the absence of central sympathetic control of the leg vasculature, postural leg vasoconstriction is preserved in spinal cord-injured individuals (SCI). This study aimed at assessing the contribution of both central and local sympathetically induced alpha-adrenergic leg vasoconstriction to head-up tilt (HUT) by including healthy individuals and SCI, who lack central sympathetic baroreflex control over the leg vascular bed.

METHODS

In 10 controls and nine SCI the femoral artery was cannulated for drug infusion. Upper leg blood flow (LBF) was measured bilaterally using venous occlusion strain gauge plethysmography before and during 30 degrees HUT throughout intra-arterial infusion of saline or the non-selective alpha-adrenergic receptor antagonist phentolamine respectively. Additionally, in six controls the leg vascular response to the cold pressor test was assessed during continued infusion of phentolamine, in order to confirm complete alpha-adrenergic blockade by phentolamine.

RESULTS

During infusion of phentolamine HUT still caused vasoconstriction in both groups: leg vascular resistance (mean arterial pressure/LBF) increased by 10 +/- 2 AU (compared with 12 +/- 2 AU during saline infusion), and 13 +/- 3 AU (compared with 7 +/- 3 AU during saline infusion) in controls and SCI respectively.

CONCLUSION

Effective alpha-adrenergic blockade did not reduce HUT-induced vasoconstriction, regardless of intact baroreflex control of the leg vasculature. Apparently, redundant mechanisms compensate for the absence of sympathetic alpha-adrenoceptor leg vasoconstriction in response to postural stress.

Treatment of benign prostatic hyperplasia at Mater Hospital, Nairobi

OBJECTIVE

To evaluate the use of medical therapy in the management of patients with mild, moderate and severe symptoms of benign prostatic hyperplasia.

DESIGN

Prospective study.

SETTING

Private urology clinic in Mater Hospital, Nairobi between 1995 and 2005.

PATIENTS

Six hundred and eighty patients with benign prostatic hypertrophy aged 50-80 years.

RESULTS

Two hundred and eighty (43.8%) patients benefited from the drug treatment alone and were released from the clinic follow up after five years. Two hundred and seventy (42.2%) cases could not complete the five years follow up on drugs alone due to symptoms recurrence or severity or unavailability of drugs. They were removed from the drugs alone treatment and put on other interventions. Ninety (15.9%) cases were operated on based on their decision and insistence or severity of their symptoms or no drugs response.

CONCLUSIONS

This observational study confirms that medical treatment is beneficial in the management of benign prostatic hyperplasia (BPH) and is cheap and gives better first line option of treatment choice to many patients. It also gives hopes to the surgical risk patients. The quality of life (QOL) of patients and their family disturbance is also improved.

A role of intravesical capsaicin instillation in benign prostatic hyperplasia with overactive bladder symptoms: the first reported study in the literature

OBJECTIVE

To study the treatment efficacy of capsaicin, in the cases of benign prostatic hyperplasia with overactive bladder symptoms.

MATERIAL AND METHOD

A prospective study of 20 benign prostatic hyperplasia patients whose overactive bladder symptoms were not improved by alpha1 blockers. All of them underwent intravesical capsaicin instillation at the Faculty of Medicine Siriraj Hospital, Bangkok, between 2004 and 2006. Both clinical and urodynamic data were evaluated before and after treatment.

RESULTS

Mean urgency decreased from 6.7 +/- 5.1 at baseline to 2.0 +/- 2.3 (p < 0.005), 1.4 +/- 2.4 (p < 0.005), and 1.3 +/- 2.2 (p < 0.005) at 1, 3, and 6 months. Mean urge incontinence decreaseD from 1.7 +/- 3.5 at baseline to 0.5 +/- 1.3 (p = 0.148), 0.4 +/- 1.2 (p = 0.114), and 0.3 +/- 1.1 (p = 0.085) at 1, 3, and 6 months. Mean urinary frequency decreased from 13.7 +/- 3.3 at baseline to 10.5 +/- 2.8 (p < 0.005), 9.6 +/- 2.0 (p < 0.005), and 9.5 +/- 2.6 (p < 0.005) at 1, 3, and 6 months. Mean nocturia decreased from 4.7 +/- 2.4 at baseline to 3.1 +/- 2.2 (p < 0.005), 2.7 +/- 1.2 (p < 0.005), and 2.9 +/- 1.6 (p < 0.005) at 1, 3, and 6 months. Mean first desire to void increased from 172.5 +/- 100.4 ml at baseline to 210.6 +/- 99.5 ml (p = 0.016) at 1 month. Mean maximal cystometric capacity increased from 350.3 +/- 165.9 ml at baseline to 397.4 +/- 165.7 ml (p = 0.012) at 1 month. Peak flow rate, detrusor pressure, and post void residual urine were not affected No serious adverse effect occurred in this study.

CONCLUSION

Intravesical capsaicin instillation is an effective treatment for overactive bladder symptoms in benign prostatic hyperplasia patients.

The Emerging Epidemic of Methamphetamine-Induced Aortic Dissections

The clinical presentation, treatment, and outcomes of six consecutive patients presenting with acute aortic dissection secondary to hypertensive crises from methamphetamine use is described. Data were obtained prospectively from the expanded STS clinical database of the division of cardiothoracic surgery at the University of Washington, but reviewed in a retrospective fashion. These patients represent 5.5% of all patients diagnosed and treated for aortic dissection in the same time period (6/109) and 20% of all patients with aortic dissection under the age of 50 years (6/30). We conclude that young patients (<age 50 years old) presenting with acute aortic dissections should be routinely tested for methamphetamine. Positive urine tests should be confirmed with chromatography-mass spectrometry (GC-MS). Beta and alpha blockers should be used instead of the more typical beta blockade alone. We recommend the addition and documentation of intense, long-term drug rehabilitation program along with routine periodic clinical and radiographic follow-up to prevent secondary aneurysmal dilation of remaining pathological aorta.

Effect of Sildenafil and Rolipram on Adrenergic Responses in Isolated Human and Monkey Corpus Cavernosum

OBJECTIVE

Evaluate and compare effects of phosphodiesterase inhibitors (PDEIs), sildenafil and rolipram, on adrenergic contractile responses of human and monkey cavernosal smooth muscle.

METHODS

Human penises were obtained from patients undergoing gender reassignment surgery. Isolated human and monkey corpus cavernosum (CC) strips were suspended in tissue bath chambers for isometric tension experiments. The effects of the drugs on precontracted monkey and human CC and neurogenic contractions in human CC were investigated.

RESULTS

Both sildenafil and rolipram induced concentration-dependent relaxations of human and monkey CC strips precontracted with noradrenaline (NA). The IC(50) values, determined by reverse regression for nitroglycerin (NTG), isoprenaline, and sildenafil in monkey CC, were, respectively, 1.5+/-0.9x10(-7) M, 3.7+/-0.6x10(-6) M, and 1.7+/-0.7x10(-5) M. Similarly, in human CC muscle, sildenafil was weaker than NTG as a muscle relaxant. Sildenafil, 1.5 microM, reduced neurogenic contractions in human CC due to stimulation of predominantly adrenergic nerves. The suppressant effect of sildenafil on adrenergic transmission was attenuated in CC strips pretreated with N omega-nitro-L-arginine and overcome with a higher stimulus frequency or tetraethylammonium. Rolipram partially inhibited adrenergic excitatory response but without significantly affecting NA-induced contraction.

CONCLUSIONS

Sildenafil and rolipram induced concentration-dependent reversal of human and monkey CC tone mediated by NA. Both PDEIs attenuated contractile adrenergic response of human CC to electrical stimulation. The results also underline the importance of the cyclic adenosine monophosphate-dependent signalling pathway in regulating the tone. PDE4 inhibition in CC is an additional mechanism for erection and potential therapeutic adjunct.

JP-1302: a new tool to shed light on the roles of alpha2C-adrenoceptors in brain

The discovery of JP-1302 as a selective, high affinity antagonist at the alpha2C-adrenoceptor will enable researchers to probe the functional role and address the therapeutic utility of this potentially highly important adrenoceptor subtype.

Frequency and pattern dependence of adrenergic and purinergic vasoconstriction in rat skeletal muscle arteries

Sympathetic nerves fire in bursts followed by brief periods of quiescence. Periods of quiescence may be a valuable part of coding for different neurotransmitters. We compared adrenergic- and non-adrenergic-mediated vasoconstriction with repeating burst patterns versus constant frequency stimulation. Seventeen rats were killed, and the femoral arteries dissected out and mounted in organ tissue baths at 37 degrees C and pH 7.4. Field stimulation was applied to artery rings from five rats at constant frequencies of 2-6 Hz for 144 impulses. In 12 rats, artery rings were stimulated with two burst pattern protocols consisting of repeating pairs, triplets, quadruplets or sextuplets performed using either 8 or 30 Hz as the instantaneous frequency for a total of 144 impulses. All protocols were repeated with the P2 purinergic antagonist pyridoxal-phosphate-6-azophenyl-2'4'-disulphonic acid (PPADs; 0.42 m) or the alpha(1)-antagonist prazosin (1.59 microM). Tension was decreased by the addition of the P2 antagonist PPADs (P < 0.05). Prazosin abolished tension at all constant frequencies (P < 0.05). P2 and alpha(1)-antagonism decreased tension with 8 and 30 Hz burst pattern field stimulation. However, the magnitude of decrease in tension with prazosin was less with burst patterns compared to the same average constant frequencies (P < 0.05). It appears that P2X receptors and alpha(1)-receptors in the femoral artery are sensitive to frequency and patterns of electrical stimulation.

Antidepressant-like activity of n-hexane extract of nutmeg (Myristica fragrans) seeds in mice

The present study was undertaken to investigate the effect of an n-hexane extract of Myristica fragrans seeds on depression in mice by using the forced swim test (FST) and the tail suspension test (TST). M. fragrans extract (5, 10, and 20 mg/kg) was administered orally for 3 successive days to different groups of Swiss male young albino mice. M. fragrans extract significantly decreased immobility periods of mice in both the FST and the TST. The 10 mg/kg dose was found to be most potent, as indicated by the greatest decrease in the immobility period compared with the control. Furthermore, this dose of the extract was found to have comparable potency to imipramine (15 mg/kg i.p.) and fluoxetine (20 mg/kg i.p.). The extract did not have a significant effect on locomotor activity of mice. Prazosin (62.5 microg/kg i.p.; an alpha (1)-adrenoceptor antagonist), sulpiride (50 mg/kg i.p.; a selective D(2) receptor antagonist), and p-chlorophenylalanine (100 mg/kg i.p.; an inhibitor of serotonin synthesis) significantly attenuated the M. fragrans extract-induced antidepressant-like effect in the TST. Thus, extract of M. fragrans elicited a significant antidepressant-like effect in mice, when assessed in both the TST and the FST. The antidepressant-like effect of the extract seems to be mediated by interaction with the adrenergic, dopaminergic, and serotonergic systems.

Are generic formulations of carvedilol of inferior pharmaceutical quality compared with the branded formulation?

INTRODUCTION

Carvedilol is a comprehensive beta(1)-, beta(2)-, and alpha(1)-adrenoreceptor blocker marketed as Dilatrend by F. Hoffmann-La Roche Ltd. (Roche) and as Coreg by GlaxoSmithKline for the treatment of hypertension, stable angina pectoris, post myocardial infarction with left ventricular dysfunction and all degrees of symptomatic chronic heart failure.

OBJECTIVES

In this report, the pharmaceutical qualities of Dilatrend 6.25 mg, 12.5 mg and 25 mg tablets and 35 randomly selected carvedilol generic products from 20 manufacturers in 19 countries have been assessed according to the European Pharmacopoeia and the Roche specifications.

METHODS

The generic products were subjected to four key tests: carvedilol content, tablet hardness, tablet dissolution and purity.

RESULTS

All three Dilatrend strengths conformed to specifications. At least 17/35 (48.6%) generic products failed the specifications due to: incorrect mean carvedilol content (outside 95-105%) - three products; excess impurities (> 0.3%) - one product; incorrect tablet hardness (outside 30-70 N) - 11 products; inadequate dissolution (< 75% in 30 min) - nine products. Seven products (20%) failed two tests, generally hardness and dissolution.

CONCLUSION

The dose-for-dose substitution of the original formulation of carvedilol (Dilatrend) with a pharmaceutically different, and possibly inferior, generic copy may conceivably result in a change in the efficacy of the treatment, because of an unanticipated change in pharmacokinetics or bioequivalence, and/or in a change in tolerability due to impurities.

Sexual dimorphism in the renin-angiotensin system in aging spontaneously hypertensive rats

In young adult spontaneously hypertensive rats (SHR), mean arterial pressure (MAP) is higher in males than in females and inhibition of the renin-angiotensin system (RAS) eliminates this sex difference. After cessation of estrous cycling in female SHR, MAP is similar to that in male SHR. The purpose of this study was to determine the role of the RAS in maintenance of hypertension in aging male and female SHR. At 16 mo of age, MAP was similar in male and female SHR (183+/-5 vs. 193+/-8 mmHg), and chronic losartan (40 mg.kg-1.day-1 po for 3 wk) reduced MAP by 52% (to 90+/-8 mmHg, P<0.05 vs. control) in males and 37% (to 123+/-11 mmHg, P<0.05 vs. control) in females (P<0.05, females vs. males). The effect of losartan on angiotensin type 1 (AT1) receptor blockade was similar: MAP responses to acute doses of ANG II (62.5-250 ng/kg) were blocked to a similar extent in losartan-treated males and females. F2-isoprostane excretion was reduced with losartan more in males than in females. There were no sex differences in plasma renin activity, plasma angiotensinogen or ANG II, or renal expression of AT1 receptors, angiotensin-converting enzyme, or renin. However, renal angiotensinogen mRNA and protein expression was higher in old males than females, whereas renal ANG II was higher in old females than males. The data show that, in aging SHR, when blood pressures are similar, there remains a sexual dimorphism in the response to AT1 receptor antagonism, and the differences may involve sex differences in mechanisms responsible for oxidative stress with aging.

Potential vascular α1-adrenoceptor blocking properties of an array of 5-HT receptor ligands in the rat

This study set out to analyse the potential ability of some 5-hydroxytryptamine (5-HT) receptor ligands widely used in cardiovascular experimental models to interact with vascular alpha1-adrenoceptors in the pithed rat. These ligands included: methiothepin, methysergide and metergoline (5-HT(1)/5-HT2); WAY-100635, buspirone, ipsapirone and 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (5-HT(1A)); GR127935 (5-HT(1B/1D)); ketanserin, ritanserin, spiperone and pizotifen (5-HT2); granisetron and metoclopramide (5-HT3); tropisetron (5-HT3/5-HT4); ergotamine (5-HT(1B/1D), 5-ht(5A/5B)); clozapine (5-HT6/5-HT7); as well as LY215840 and mesulergine (5-HT2/5-HT7). For this purpose, the increases in diastolic blood pressure produced by the selective alpha1-adrenoceptor agonist, phenylephrine, were analysed before and after the above antagonists or saline. The adrenoceptor antagonist properties of prazosin (alpha1) and yohimbine (alpha2) were also analysed for comparison. Thus, the phenylephrine-induced vasopressor responses were dose-dependently antagonised with the following apparent rank order of potency by: prazosin > or = methiothepin > ketanserin > clozapine > or = lisuride >> buspirone; this potency correlates with the affinity of these compounds for alpha1-adrenoceptor binding sites. In contrast, the other compounds were either devoid of any blocking effect on--or even potentiated (i.e. lisuride, methysergide, 8-OH-DPAT, granisetron and GR127935)--the responses to phenylephrine. These results show that methiothepin, ketanserin, clozapine, lisuride and buspirone can block alpha1-adrenoceptors in the rat systemic vasculature.

Assessment of cognitive function in patients with essential hypertension treated with lercanidipine

OBJECTIVES

The aim of this longitudinal, open-label, comparative, multicenter study was to assess cognitive function in hypertensive patients receiving mid-term treatment with lercanidipine.

METHODS

Hypertensive patients aged 40 years or older were treated with lercanidipine (10 mg daily) after 7-10 days washout period. The duration of the study was 6 months. Blood pressure (BP) was measured every 4 weeks (JNC 6th report). In patients with inadequate BP control, doxazosin was added and up-titrated. At baseline and after 6 months of treatment, cognitive function was evaluated using the Spanish validated version of the Mini-Mental State Examination (MMSE) and the Trail Making Test (TMT).

RESULTS

In the study population of 467 patients, BP decreased from 154.4/95.3 mmHg at baseline to 134.8/80.7 mmHg at 6 months. At the end of the study, 98% of patients were receiving lercanidipine, 20% an angiotensin-converting enzyme inhibitor, and 6% doxazosin. Adequate BP control was obtained in 68% of patients. The mean (standard deviation) MMSE scores improved from 32.35 (2.59) to 33.25 (2.36) (p < 0.0001). Patients with good BP control scored significantly better than those with inadequate BP control (p < 0.05), which was already observed at the first month.

CONCLUSIONS

The third-generation calcium channel antagonist, lercanidipine, improved cognitive function after 6 months of treatment especially in patients with good BP control, suggesting that improvements in cognitive function may be associated with a decrease in BP.

Attenuation of visceral nociception by alpha- and beta-amyrin, a triterpenoid mixture isolated from the resin of Protium heptaphyllum, in mice

In the search for novel natural compounds effective against visceral nociception, the triterpenoid mixture alpha- and beta-amyrin, isolated from Protium heptaphyllum resin, was assessed in two established mouse models of visceral nociception. Mice were pretreated orally with alpha- and beta-amyrin (3, 10, 30, and 100 mg/kg) or vehicle, and the pain-related behavioral responses to intraperitoneal cyclophosphamide or to intracolonic mustard oil were analyzed. The triterpenoid mixture showed a dose-related significant antinociception against the cyclophosphamide-induced bladder pain, and at 100 mg/kg, the nociceptive behavioral expression was almost completely suppressed. Intracolonic mustard oil-induced nociceptive behaviors were maximally inhibited by 10 mg/kg alpha- and beta-amyrin mixture in a naloxone-reversible manner. While pretreatment with ruthenium red (3 mg/kg, s. c.), a non-specific transient receptor potential cation channel V1 (TRPV1) antagonist, also caused significant inhibition, the alpha (2)-adrenoceptor antagonist, yohimbine (2 mg/kg, s. c.), showed no significant effect. The triterpene mixture (10 mg/kg, p. o.) neither altered significantly the pentobarbital sleeping time, nor impaired the ambulation or motor coordination in open-field and rotarod tests, respectively, indicating the absence of sedative or motor abnormalities that could account for its antinociception. These results indicate that the antinociceptive potential of alpha- and beta-amyrin possibly involves the opioid and vanilloid (TRPV1) receptor mechanisms and further suggests that it could be useful to treat visceral pain of intestinal and pelvic origins.

Effect of terazosin on tissue vascularity and apoptosis in transitional cell carcinoma of bladder

OBJECTIVES

To present a pilot study to determine whether the alpha1-adrenoceptor antagonist terazosin can induce apoptosis in transitional cell carcinoma (TCC) of the bladder, similar to the effect seen with prostate cancer. The alpha1-adrenoceptor antagonist terazosin has recently been shown to induce apoptosis in prostate cancer cells both in vitro and in vivo and to reduce prostatic tissue vascularity by potentially affecting endothelial cell adhesion.

METHODS

The records of 24 men who underwent radical cystectomy for TCC of the bladder at the Lexington Veterans Affairs Medical Center were reviewed. The control group consisted of 15 men who were never exposed to terazosin. The study group consisted of 9 men who were treated with terazosin before cystectomy. Sections of the bladder tumor and normal trigone were subjected to immunohistochemical analysis for microvessel density, endothelial cell CD31 expression, and apoptosis detection (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling), as well as high-molecular-weight cytokeratin staining.

RESULTS

A significant reduction in tissue vascularity (14.0 versus 19.2, P <0.05) and a significant increase in the apoptotic index (3.0% versus 1.7%, P <0.05) was detected in terazosin-treated bladder tumors compared with untreated bladder tumors. Most TCC specimens (80%) exhibited strong and consistently uniform immunostaining for high-molecular-weight cytokeratin staining.

CONCLUSIONS

These results suggest that terazosin reduces tumor vascularity and induces apoptosis in TCC of the bladder. Additional studies with more patients are necessary to reach definitive conclusions. However, considering the proven apoptotic action of terazosin in prostatic tissue, this study may have implications for the use of terazosin in the treatment of bladder TCC.

A review of controlled trials in the pharmacological treatment of premature ejaculation

Premature ejaculation is a common sexual problem which presents to genitourinary (GU) medicine services. Five main treatment approaches have been used in clinical trials: behavioural therapy, antidepressants, phosphodiesterase-5 (PDE5) inhibitors, topical anaesthetic agents and alpha-blockers. We have carried out a systematic review of published pharmacological trials. All antidepressants appeared to delay ejaculation to some extent at all doses. Anaesthetic creams appeared to be as successful in slowing ejaculation as antidepressants without systemic side-effects, although some patients did experience erectile problems or unpleasant local symptoms. Anecdotally, behavioural therapy is effective and appears to have long-lasting efficacy. There is a need for quality comparative trial of behavioural therapy, topical anaesthetic agents and antidepressants, including appropriate measures of relapse, follow-up and acceptability of continuing long-term treatment.

THE COMPARISON AND EFFICACY OF 3 DIFFERENT α1-ADRENERGIC BLOCKERS FOR DISTAL URETERAL STONES

PURPOSE

alpha1-Adrenergic blockers have recently been shown to increase the rate of spontaneous passage of distal ureteral stones. We compared efficacy of 3 different alpha1-adrenergic blockers for this purpose.

MATERIALS AND METHODS

A total of 114 patients between 18 and 65 years old who had lower ureteral stones were included in the study. Patients were randomly divided into 4 groups. Group 1 consisted of 28 patients and acted as the control group. Group 2 comprised 29 patients who received tamsulosin, group 3 was 28 patients receiving terazosin and group 4 was 29 patients receiving doxazosin. These agents were given for up to a month and hydration was also recommended simultaneously. Every week patients were controlled with x-rays of the kidneys, ureters, bladder and urinary ultrasonography. Meanwhile the number of pain episodes, analgesic dosage and the number of days for spontaneous passage of the calculi through the ureter were also recorded.

RESULTS

There were no differences between the groups with respect to age, weight, height, sex and stone size. The calculi passed through the ureter spontaneously in 15 patients in group 1 (53.57%), in 23 patients in group 2 (79.31%), in 22 patients in group 3 (78.57%), and in 22 patients in group 4 (75.86%). In groups 2 to 4 the number of pain episodes, expulsion time and analgesic dosage were found to be lower compared with those in group 1.

CONCLUSIONS

alpha1-Adrenergic blockers increase the frequency of spontaneous passage of the distal ureteral calculi. All 3 agents tested were equally efficacious.

Selective inhibition of alpha1A-adrenergic receptor signaling by RGS2 association with the receptor third intracellular loop

Regulators of G-protein signaling (RGS) proteins act directly on Galpha subunits to increase the rate of GTP hydrolysis and to terminate signaling. However, the mechanisms involved in determining their specificities of action in cells remain unclear. Recent evidence has raised the possibility that RGS proteins may interact directly with G-protein-coupled receptors to modulate their activity. By using biochemical, fluorescent imaging, and functional approaches, we found that RGS2 binds directly and selectively to the third intracellular loop of the alpha1A-adrenergic receptor (AR) in vitro, and is recruited by the unstimulated alpha1A-AR to the plasma membrane in cells to inhibit receptor and Gq/11 signaling. This interaction was specific, because RGS2 did not interact with the highly homologous alpha1B- or alpha1D-ARs, and the closely related RGS16 did not interact with any alpha1-ARs. The N terminus of RGS2 was required for association with alpha1A-ARs and inhibition of signaling, and amino acids Lys219, Ser220, and Arg238 within the alpha1A-AR i3 loop were found to be essential for this interaction. These findings demonstrate that certain RGS proteins can directly interact with preferred G-protein-coupled receptors to modulate their signaling with a high degree of specificity.

Amygdala and "emotional" modulation of the relative use of multiple memory systems

The basolateral amygdala modulates the cognitive and habit memory processes mediated by the hippocampus and caudate nucleus, respectively. The present experiments used a plus-maze task that can be acquired using either hippocampus-dependent "place" learning or caudate-dependent "response" learning to examine whether peripheral or intra-basolateral amygdala injection of anxiogenic drugs would bias rats towards the use of a particular memory system. In Experiment 1, adult male Long-Evans rats were trained to swim from the same start point to an escape platform located in a consistent goal arm, and received pre-training peripheral injections of the alpha(2)-adrenoceptor antagonists yohimbine (2.5 or 5.0 mg/kg), RS 79948-197 (0.05, 0.1, or 0.2 mg/kg), or vehicle. On a drug-free probe trial from a novel start point administered 24h following acquisition, vehicle treated rats predominantly displayed hippocampus-dependent place learning, whereas rats previously treated with yohimbine (2.5, 5.0 mg/kg) or RS 79948-197 (0.1 mg/kg) predominantly displayed caudate-dependent response learning. In Experiment 2, rats receiving pre-training intra-basolateral amygdala infusions of RS 79948-197 (0.1 microg/0.5 microl) also predominantly displayed response learning on a drug-free probe trial. The findings indicate (1) peripheral injections of anxiogenic drugs can influence the relative use of multiple memory systems in a manner that favors caudate-dependent habit learning over hippocampus-dependent cognitive learning, and (2) intra-basolateral amygdala infusion of anxiogenic drugs is sufficient to produce this modulatory influence of emotional state on the use of multiple memory systems.

Correlation between penile duplex findings and stress electrocardiography in men with erectile dysfunction

The aim of this work is to assess the association between vasculogenic erectile dysfunction (ED) and coronary artery disease in men above the age of 40 y. The study included 40 patients above 40 y of age with vasculogenic ED of more than 3 months duration. A dynamic duplex study after intracavernosal injection of a bimix solution (60 mg papaverine + 2 mg phentolamine mesylate) was carried out using a color ultrasound machine. The patients underwent a stress ECG test, carried out on a motor-driven treadmill according to the 'Bruce Protocol'. A total of 12 patients were diagnosed with positive ischemic heart disease (IHD). Their mean peak systolic velocity (PSV) was PSV = 19.58 cm/s. In all, patients were diagnosed with negative IHD; their mean PSV was 36.21 cm/s. A statistically significant difference was observed between patients with positive IHD and patients with negative IHD regarding PSV (P = 0.003). The sensitivity of a PSV of less than 35 cm/s in predicting IHD was 50% with a specificity of 100%. Positive predictive value for abnormal stress ECG to predict a PSV of less than 35 cm/s was 100%. In conclusion, the PSV of cavernosal arteries is a reliable measure for predicting IHD in patients with vasculogenic ED. Patients with a PSV of less than 35 cm/s should be referred for cardiologic assessment as they carry a real risk of having silent IHD.

Efficacy of open-label venlafaxine in subjects with major depressive disorder: associations with neuroendocrine response to serotonergic and noradrenergic probes

An open-label pilot study explored the relationship between severity of depressive symptoms and venlafaxine dose required for clinical efficacy in outpatients with major depressive disorder (MDD). The utility of the neuroendocrine response to serotonergic (ipsapirone) and noradrenergic (clonidine) probes as predictors of venlafaxine dosage required for effective treatment was also explored. Nineteen medically healthy medication-free outpatients over 18 years of age who met criteria for MDD were studied. Participants received either a 20-mg dose of ipsapirone orally, a 0.002-mg/kg intravenous dose of clonidine, or placebo. Following a 1-week single-blind placebo lead-in, all subjects were treated with immediate release venlafaxine. Low-dose responders were defined as those subjects experiencing a >50% decrease in depression score on 37.5 mg, b.i.d., and high-dose responders were defined as those subjects experiencing similar improvement on venlafaxine doses of 75 mg, b.i.d., or higher. Subjects responding to low-dose treatment had a lower mean baseline Hamilton depression score than subjects requiring high-dose treatment. Neuroendocrine and temperature responses to clonidine or ipsapirone challenges were not significantly different in the high- vs. low-dose responders. Evaluation of models of "serotonergic-responsive" and norepinephrine-responsive" depression requires larger numbers of patients.