Adrenergic inhibition facilitates normalization of extracellular potassium after cortical spreading depolarization.

Cortical spreading depolarization (CSD) is a propagating wave of tissue depolarization characterized by a large increase of extracellular potassium concentration and prolonged subsequent electrical silencing of neurons. Waves of CSD arise spontaneously in various acute neurological settings, including migraine aura and ischemic stroke. Recently, we have reported that pan-inhibition of adrenergic receptors (AdRs) facilitates the normalization of extracellular potassium after acute photothrombotic stroke in mice. Here, we have extended that mechanistic study to ask whether AdR antagonists also modify the dynamics of KCl-induced CSD and post-CSD recovery in vivo. Spontaneous neural activity and KCl-induced CSD were visualized by cortex-wide transcranial Ca2+ imaging in G-CaMP7 transgenic mice. AdR antagonism decreased the recurrence of CSD waves and accelerated the post-CSD recovery of neural activity. Two-photon imaging revealed that astrocytes exhibited aberrant Ca2+ signaling after passage of the CSD wave. This astrocytic Ca2+ activity was diminished by the AdR antagonists. Furthermore, AdR pan-antagonism facilitated the normalization of the extracellular potassium level after CSD, which paralleled the recovery of neural activity. These observations add support to the proposal that neuroprotective effects of AdR pan-antagonism arise from accelerated normalization of extracellular K+ levels in the setting of acute brain injury.

The adrenergic receptor antagonist carvedilol interacts with serotonin 2A receptors both in vitro and in vivo.

There is increasing support for the potential clinical use of compounds that interact with serotonin 2A (5-HT2A) receptors. It is therefore of interest to discover novel compounds that interact with 5-HT2A receptors. In the present study, we used computational chemistry to identify critical ligand structural features of 5-HT2A receptor binding and function. Query of compound databases using those ligand features revealed the adrenergic receptor antagonist carvedilol as a high priority match. As carvedilol is used clinically for cardiovascular diseases, we conducted experiments to assess whether it has any interactions with 5-HT2A receptors. In vitro experiments demonstrated that carvedilol has high nanomolar affinity for 5-HT2A receptors. In vivo experiments demonstrated that carvedilol increases the ethanol-induced loss of the righting reflex and suppresses operant responding in mice, and that these effects are attenuated by pretreatment with the selective 5-HT2A receptor antagonist M100907. Moreover, carvedilol did not induce the head-twitch response in mice, suggesting a lack of psychedelic effects. However, carvedilol did not activate canonical 5-HT2A receptor signaling pathways and antagonized serotonin-mediated signaling. It also reduced the head-twitch response induced by 2,5-Dimethoxy-4-iodoamphetamine, suggesting potential in vivo antagonism, allosteric modulation, or functional bias. These data suggest that carvedilol has functionally relevant interactions with 5-HT2A receptors, providing a novel mechanism of action for a clinically used compound. However, our findings do not clearly delineate the precise mechanism of action of carvedilol at 5-HT2A receptors, and additional experiments are needed to elucidate the role of 5-HT2A receptors in the behavioral and clinical effects of carvedilol.

α-Adrenergic receptor regulation of skeletal muscle blood flow during exercise in heart failure patients with reduced ejection fraction.

Patients suffering from heart failure with reduced ejection fraction (HFrEF) experience impaired limb blood flow during exercise, which may be due to a disease-related increase in α-adrenergic receptor vasoconstriction. Thus, in eight patients with HFrEF (63 ± 4 yr) and eight well-matched controls (63 ± 2 yr), we examined changes in leg blood flow (Doppler ultrasound) during intra-arterial infusion of phenylephrine (PE; an α1-adrenergic receptor agonist) and phentolamine (Phen; a nonspecific α-adrenergic receptor antagonist) at rest and during dynamic single-leg knee-extensor exercise (0, 5, and 10 W). At rest, the PE-induced reduction in blood flow was significantly attenuated in patients with HFrEF (-15 ± 7%) compared with controls (-36 ± 5%). During exercise, the controls exhibited a blunted reduction in blood flow induced by PE (-12 ± 4, -10 ± 4, and -9 ± 2% at 0, 5, and 10 W, respectively) compared with rest, while the PE-induced change in blood flow was unchanged compared with rest in the HFrEF group (-8 ± 5, -10 ± 3, and -14 ± 3%, respectively). Phen administration increased leg blood flow to a greater extent in the HFrEF group at rest (+178 ± 34% vs. +114 ± 28%, HFrEF vs. control) and during exercise (36 ± 6, 37 ± 7, and 39 ± 6% vs. 13 ± 3, 14 ± 1, and 8 ± 3% at 0, 5, and 10 W, respectively, in HFrEF vs. control). Together, these findings imply that a HFrEF-related increase in α-adrenergic vasoconstriction restrains exercising skeletal muscle blood flow, potentially contributing to diminished exercise capacity in this population.

Retrospective review of the use of as-needed hydralazine and labetalol for the treatment of acute hypertension in hospitalized medicine patients.

BACKGROUND: The aim of this study was to evaluate the use of as-needed (PRN) labetalol and hydralazine [intravenous (IV) or oral] in hospitalized medicine patients for the treatment of severe asymptomatic hypertension and to examine the potential negative outcomes associated with their use. METHODS: The electronic health record of 250 medicine patients hospitalized at the University of Colorado Hospital between November 2014 and April 2016 who received at least one dose of PRN IV or oral hydralazine or labetalol were retrospectively reviewed. The primary outcome was to describe the use of PRN antihypertensive medications in this population. RESULTS: A total of 573 PRN doses of antihypertensive medication were administered. Oral hydralazine was the most common (521 doses, 90.9%). A total of 36% of PRN administrations were given for a systolic blood pressure (SBP) <180 mmHg and diastolic blood pressure (DBP) <110 mmHg (cut-point for acute severe hypertension). No serious adverse events were related to PRN antihypertensive administration. Despite receiving at least one PRN antihypertensive medication during hospitalization, 40.8% of patients were not continued on their home antihypertensive medication(s) while hospitalized, and 62.4% of patients did not have their home regimens intensified at discharge. CONCLUSION: As-needed oral hydralazine is frequently prescribed for acute blood pressure lowering with administration thresholds often less than what are used to define acute severe hypertension. Many patients are prescribed PRN antihypertensive medication instead of being continued on their home regimens, and most patients do not have the intensity of their home regimens increased. Providers need to be educated about the use of PRN antihypertensive medication for the management of severe asymptomatic hypertension in the hospital setting.

Dissociable effects of systemic and orbitofrontal administration of adrenoceptor antagonists on yohimbine-induced motor impulsivity.

The α2-adrenoceptor antagonist, yohimbine, is commonly used as a pharmacological stressor. Its behavioural effects are typically attributed to elevated noradrenaline release via blockade of central, inhibitory autoreceptors. We have previously reported that yohimbine increases motor impulsivity in rats on the five-choice serial reaction time task (5CSRTT), a cognitive behavioural assessment which measures motor impulsivity and visuospatial attention. Furthermore, this effect depended on cyclic adenomonophosphate (cAMP) signalling via cAMP response element binding (CREB) protein in the orbitofrontal cortex (OFC). However, the role of specific adrenoceptors in this effect is not well-characterised. We therefore investigated whether the pro-impulsive effects of systemic yohimbine could be reproduced by direct administration into the OFC, or attenuated by intra-OFC or systemic administration of prazosin and propranolol-antagonists at the α1- and ß-adrenoceptor, respectively. Male Long-Evans rats were trained on the 5CSRTT and implanted with guide cannulae aimed at the OFC. Systemically administered α1- or ß-adrenoceptor antagonists attenuated yohimbine-induced increases in premature responding. In contrast, local infusion of yohimbine into the OFC reduced such impulsive responding, while blockade of α1- or ß-adrenoceptors within the OFC had no effect on either basal or yohimbine-stimulated motor impulsivity. Direct administration of selective antagonists at the α1-, α2- or ß-adrenoceptor into the OFC therefore produce clearly dissociable effects from systemic administration. Collectively, these data suggest that the pro-impulsivity effect of yohimbine can be modulated by adrenergic signalling in brain areas outside of the OFC, in addition to non-adrenergic signalling pathways within the OFC.

Identification and management of alcohol withdrawal syndrome.

Symptoms of alcohol withdrawal syndrome (AWS) may develop within 6-24 h after the abrupt discontinuation or decrease of alcohol consumption. Symptoms can vary from autonomic hyperactivity and agitation to delirium tremens. The gold-standard treatment for AWS is with benzodiazepines (BZDs). Among the BZDs, different agents (i.e., long-acting or short-acting) and different regimens (front-loading, fixed-dose or symptom-triggered) may be chosen on the basis of patient characteristics. Severe withdrawal could require ICU admission and the use of barbiturates or propofol. Other drugs, such as α2-agonists (clonidine and dexmetedomidine) and ß-blockers can be used as adjunctive treatments to control neuroautonomic hyperactivity. Furthermore, neuroleptic agents can help control hallucinations. Finally, other medications for the treatment for AWS have been investigated with promising results. These include carbamazepine, valproate, sodium oxybate, baclofen, gabapentin and topiramate. The usefulness of these agents are discussed.

To reheat, or to not reheat: that is the question: the efficacy of a local reheating protocol on mechanisms of cutaneous vasodilatation.

The aim of this study is to determine the effect of repeated bouts of local skin heating on the roles of nitric oxide synthase (NOS) and sympathetic nerves in cutaneous vasodilatation. In 3 repeated-heating protocols skin blood flux of the forearm and leg was measured using laser-Doppler flowmetry and data are presented as cutaneous vascular conductance (CVC; flux/blood pressure). Local heating was performed from 33°C (thermoneutral) to 42°C at 0.5°C·10s(-1), allowed to cool passively for ~60-min, then reheated at the same rate. In protocol 1, CVC was measured in response to repeated heating. In protocol 2, NOS was inhibited with N(G)-nitro-l-arginine methyl ester (L-NAME) and in protocol 3, sympathetic nerve blockade was achieved with bretylium tosylate (BT), both infused via intradermal microdialysis. In protocol 1, there were no differences (P>0.05) in CVC at either the forearm (88±4 vs. 86±4%max) or the leg (97±4 vs. 96±6%max) between heating bouts. In protocol 2, no differences (P>0.05) in CVC were observed between heating bouts at L-NAME treated sites at either the forearm (55±3 vs. 51±4%max) or the leg (71±3 vs. 70±4%max) . In protocol 3, there were differences (P<0.001) between BT treated sites when comparing the first and second bouts of heating for both the forearm (75±3 vs. 88±4%max) and the leg (79±3 vs. 97±4%max). The effect of sympathetic blockade on CVC responses to local heating was abolished following repeated bouts of heating. Consequently, it is our suggestion that when examining mechanisms of skin blood flow control, investigators use single bouts of local heating.

Lack of limb or sex differences in the cutaneous vascular responses to exogenous norepinephrine.

The cutaneous circulation is used to examine vascular adrenergic function in clinical populations; however, limited studies have examined whether there are regional limb and sex differences in microvascular adrenergic responsiveness. We hypothesized that cutaneous adrenergic responsiveness would be greater in the leg compared with the arm and that these regional limb differences would be blunted in young women (protocol 1). We further hypothesized that cutaneous vasoconstriction to exogenous norepinephrine (NE) during ß-adrenergic receptor antagonism would be augmented in young women (protocol 2). In protocol 1, one microdialysis fiber was placed in the skin of the calf and the ventral forearm in 20 healthy young adults (11 men and 9 women). Laser-Doppler flowmetry was used to measure red blood cell flux in response to graded intradermal microdialysis infusions of NE (10(-12) to 10(-2) M). In protocol 2, three microdialysis fibers were placed in the forearm (6 men and 8 women) for the local perfusion of lactated Ringer (control), 5 mM yohimbine (α-adrenergic receptor antagonist), or 2 mM propranolol (ß-adrenergic receptor antagonist) during concurrent infusions of NE (10(-12) to 10(-2) M). There were no limb or sex differences in cutaneous adrenergic responsiveness (logEC50) to exogenous NE. During α-adrenergic receptor blockade, women had greater exogenous NE-induced cutaneous vasodilation at the lowest doses of NE (10(-12) to 10(-10) M). Collectively, these data indicate that there are no limb or sex differences in cutaneous adrenergic responsiveness to exogenous NE; however, young women have a greater ß-adrenergic receptor-mediated component of the vascular responsiveness to exogenous NE.

Involvement of the monoaminergic system in the antidepressant-like activity of chromium chloride in the forced swim test.

Bio-metal chromium(III) is a crucial microelement for the proper functioning of living organisms. Previous preclinical and clinical studies reported its potential antidepressant properties. The aim of the present study was to examine the effect of antidepressants and noradrenergic and dopaminergic receptor antagonists on chromium chloride (CrCl3) activity in the forced swim test (FST) in mice and rats. Imipramine (5 mg/kg), fluoxetine (5 mg/kg) and reboxetine (5 mg/kg) but not bupropion (1 mg/kg), administered jointly with CrCl3 at a dose of 6 mg/kg, reduced the immobility time in the FST in mice. The reduction of the immobility time induced by the active dose (12 mg/kg) of CrCl3 was completely abolished by propranolol (2 mg/kg, ß-adrenoceptor antagonist), SCH 23390 (0.5 mg/kg, a dopamine D1 receptor antagonist), and partially by prazosin (1 mg/kg, an α1-adrenoceptor antagonist), yohimbine (1 mg/kg, an α2-adrenoceptor antagonist) and sulpiryd (50 mg/kg, a dopamine D2/D3 receptor antagonist) administration. The locomotor activity was significantly reduced by CrCl3 + reboxetine treatment, which did not influence the reboxetine enhancement of the antidepressant-like effect of CrCl3 in the FST. Moreover, CrCl3 at a dose of 32 mg/kg (although not at 12 mg/kg) significantly reduced the immobility and enhanced the climbing (but not swimming) time in the FST in rats, which indicates the involvement of the noradrenergic pathway in this effect. The present study indicates that the antidepressant-like activity of chromium in the FST is dependent (although to a different extent) on the noradrenergic, dopaminergic and serotonin systems.

Sleep drives metabolite clearance from the adult brain.

The conservation of sleep across all animal species suggests that sleep serves a vital function. We here report that sleep has a critical function in ensuring metabolic homeostasis. Using real-time assessments of tetramethylammonium diffusion and two-photon imaging in live mice, we show that natural sleep or anesthesia are associated with a 60% increase in the interstitial space, resulting in a striking increase in convective exchange of cerebrospinal fluid with interstitial fluid. In turn, convective fluxes of interstitial fluid increased the rate of ß-amyloid clearance during sleep. Thus, the restorative function of sleep may be a consequence of the enhanced removal of potentially neurotoxic waste products that accumulate in the awake central nervous system.

Evidence for the involvement of peripheral ß-adrenoceptors in delayed liquid gastric emptying induced by dipyrone, 4-aminoantipyrine, and antipyrine in rats.

Dipyrone (Dp), 4-aminoantipyrine (AA), and antipyrine (At) delay liquid gastric emptying (GE) in rats. We evaluated adrenergic participation in this phenomenon in a study in male Wistar rats (250-300 g) pretreated subcutaneously with guanethidine (GUA), 100 mg·kg-1·day-1, or vehicle (V) for 2 days before experimental treatments. Other groups of animals were pretreated intravenously (iv) 15 min before treatment with V, prazosin (PRA; 1 mg/kg), yohimbine (YOH; 3 mg/kg), or propranolol (PRO; 4 mg/kg), or with intracerebroventricular (icv) administration of 25 µg PRO or V. The groups were treated iv with saline or with 240 µmol/kg Dp, AA, or At. GE was determined 10 min later by measuring the percentage of gastric retention (%GR) of saline labeled with phenol red 10 min after gavage. %GR (mean ± SE, n=8) indicated that GUA abolished the effect of Dp (GUA vs V=31.7 ± 1.6 vs 47.1 ± 2.3%) and of At (33.2 ± 2.3 vs 54.7 ± 3.6%) on GE and significantly reduced the effect of AA (48.1 ± 3.2 vs 67.2 ± 3.1%). PRA and YOH did not modify the effect of the drugs. %GR (mean ± SE, n=8) indicated that iv, but not icv, PRO abolished the effect of Dp (PRO vs V=29.1 ± 1.7 vs 46.9 ± 2.7%) and At (30.5 ± 1.7 vs 49 ± 3.2%) and significantly reduced the effect of AA (48.4 ± 2.6 vs 59.5 ± 3.1%). These data suggest activation of peripheral ß-adrenoceptors in the delayed GE induced by phenylpyrazolone derivatives.

Contributions of endothelial nitric oxide synthase, noradrenaline, and neuropeptide Y to local warming-induced cutaneous vasodilatation in men.

We performed a two-part study to determine the roles of endothelial nitric oxide synthase (eNOS) and the vasoconstrictor nerves neurotransmitters noradrenaline (NA) and neuropeptide Y (NPY) in the cutaneous vasodilator response to local skin warming. Forearm skin sites were instrumented with intradermal microdialysis fibres, local heaters, and laser-Doppler flow (LDF) probes. Sites were locally heated from 34 to 42°C. LDF was expressed as cutaneous vascular conductance (CVC; LDF/mean arterial pressure). In Part I, we tested whether sympathetic noradrenergic nerves acted via eNOS. In 8 male participants, treatments were as follows: 1) untreated; 2) bretylium tosylate (BT), preventing sympathetic neurotransmitter release; 3) l-NAA to inhibit eNOS; and 4) combined BT+l-NAA. At treated sites, the initial peak response was markedly reduced, and the plateau phase response to 35min of local warming was also reduced (P<0.05), which was not different among those sites (P>0.05). In Part II, we tested whether NA and NPY were involved in the vasodilator response to local warming. In Part IIa, treatments were: 1) untreated; 2) propranolol and yohimbine to antagonize α- and ß-receptors; 3) l-NAA; and 4) combined propranolol, yohimbine, and l-NAA. In Part IIb, conditions were: 1) untreated; 2) BIBP to antagonize Y1-receptors; 3) l-NAA; and 4) combined BIBP and l-NAA. All treatments caused a reduction in the initial peak and plateau responses to local skin warming (P<0.05). The results of Part II indicate that both NA and NPY play roles in the cutaneous vasodilator response and their actions are achieved via eNOS. These data indicate that NA and NPY are involved in the initial, rapid rise in skin blood flow at the onset of local skin warming. However, their vasodilator actions in response to local skin warming appears to be manifested through eNOS.

Evidence for the involvement of peripheral -adrenoceptors in delayed liquid gastric emptying induced by dipyrone, 4-aminoantipyrine, and antipyrine in rats

Dipyrone (Dp), 4-aminoantipyrine (AA), and antipyrine (At) delay liquid gastric emptying (GE) in rats. We evaluated adrenergic participation in this phenomenon in a study in male Wistar rats (250-300 g) pretreated subcutaneously with guanethidine (GUA), 100 mg·kg−1·day−1, or vehicle (V) for 2 days before experimental treatments. Other groups of animals were pretreated intravenously (iv) 15 min before treatment with V, prazosin (PRA; 1 mg/kg), yohimbine (YOH; 3 mg/kg), or propranolol (PRO; 4 mg/kg), or with intracerebroventricular (icv) administration of 25 µg PRO or V. The groups were treated iv with saline or with 240 µmol/kg Dp, AA, or At. GE was determined 10 min later by measuring the percentage of gastric retention (%GR) of saline labeled with phenol red 10 min after gavage. %GR (mean±SE, n=8) indicated that GUA abolished the effect of Dp (GUA vs V=31.7±1.6 vs 47.1±2.3%) and of At (33.2±2.3 vs 54.7±3.6%) on GE and significantly reduced the effect of AA (48.1±3.2 vs 67.2±3.1%). PRA and YOH did not modify the effect of the drugs. %GR (mean±SE, n=8) indicated that iv, but not icv, PRO abolished the effect of Dp (PRO vs V=29.1±1.7 vs 46.9±2.7%) and At (30.5±1.7 vs 49±3.2%) and significantly reduced the effect of AA (48.4±2.6 vs 59.5±3.1%). These data suggest activation of peripheral β-adrenoceptors in the delayed GE induced by phenylpyrazolone derivatives.

Experimental treatments for cocaine toxicity: a difficult transition to the bedside.

Cocaine is a commonly abused illicit drug that causes significant morbidity and mortality. Although there is no true antidote to cocaine toxicity, current management strategies address the life-threatening systemic effects, namely hyperthermia, vasospasm, and severe hypertension. Clinicians rely on rapid cooling, benzodiazepines, and α-adrenergic antagonists for management, with years of proven benefit. Experimental agents have been developed to more effectively treat acute toxicity. Pharmacodynamic approaches include antipsychotics that are thought to interfere with cocaine's actions at several neurotransmitter receptors. However, these medications may worsen the consequences of cocaine toxicity as they can interfere with heat dissipation, cause arrhythmias, and lower the seizure threshold. Pharmacokinetic approaches use cocaine-metabolizing enzymes, such as butyrylcholinesterase (BChE), cocaine hydrolase (CocH), and bacterial cocaine esterase (CocE). Experimental models with these therapies improve survival, primarily when administered before cocaine, although newer evidence demonstrates beneficial effects shortly after cocaine toxicity has manifested. CocE, a foreign protein, can induce an immune response with antibody formation. When enzyme administration was combined with vaccination against the cocaine molecule, improvement in cocaine-induced locomotor activity was observed. Finally, lipid emulsion rescue has been described in human case reports as an effective treatment in patients with hemodynamic compromise because of cocaine, which correlates well with its documented benefit in toxicity due to other local anesthetics. A pharmaceutical developed from these concepts will need to be expedient in onset and effective with minimal adverse effects while at the same time being economical.

Clinical benefit of eplerenone in patients with mild symptoms of systolic heart failure already receiving optimal best practice background drug therapy: analysis of the EMPHASIS-HF study.

BACKGROUND: In EMPHASIS-HF (Eplerenone in Mild Patients Hospitalization and Survival Study in Heart Failure), eplerenone significantly reduced major cardiovascular events versus placebo in 2737 patients with mild symptoms of heart failure and an ejection fraction of <35%, in addition to recommended therapy. However, it is not known whether such benefits were preserved in patients receiving optimal background drug therapy, that is, high doses of angiotensin-converting enzyme inhibitor (ACEi, or angiotensin receptor blocker), ß-blocker, or both drug classes. METHODS AND RESULTS: We further analyzed EMPHASIS-HF according to the use and dose of these background drug classes. Patients receiving ≥ 50% of target dose were considered to be receiving high doses; patients on <50% or no drug comprised the low-dose group. The primary end point of the study (cardiovascular death/heart failure hospitalization), as well as all-cause mortality, was evaluated in this way. The beneficial clinical effects of eplerenone (as observed in the main study) were preserved for the EMPHASIS-HF primary end point in patients receiving higher doses of ACEi or angiotensin receptor blocker, ß-blocker, or both (hazard ratio for eplerenone versus placebo, ACEi/angiotensin receptor blocker: high dose, 0.67; low dose, 0.65; ß-blockers: high dose, 0.55; low dose, 0.72; both ACEi/angiotensin receptor blocker and ß-blocker: high dose, 0.59; low dose, 0.68; P value for interaction 0.80, 0.15, and 0.53, respectively), as well as for all-cause mortality. There were no major safety issues, except a borderline increased risk of hypotension with eplerenone in those on high-dose ACEi or ACEi/ß-blocker. CONCLUSIONS: Eplerenone provides substantial benefit on major events (with an acceptable safety profile) in patients with mild symptoms of systolic heart failure, even in those already receiving high doses of standard background therapies.

The action of kisspeptin-13 on passive avoidance learning in mice. Involvement of transmitters.

Kisspeptins are G protein-coupled receptor ligands originally identified as human metastasis suppressor gene products that have the ability to suppress melanoma and breast cancer metastasis and recently found to play an important role in initiating the secretion of gonadotropin-releasing hormone at puberty. Kisspeptin-13 is an endogenous isoform that consists of 13 amino acids. The action of kisspeptin in the regulation of gonadal function has been widely studied, but little is known as concerns its function in limbic brain structures. In the brain, the gene is transcribed within the hippocampal dentate gyrus. This paper reports on a study the effects of kisspeptin-13 on passive avoidance learning and the involvement of the adrenergic, serotonergic, cholinergic, dopaminergic and GABA-A-ergic, opiate receptors and nitric oxide in its action in mice. Mice were pretreated with a nonselective α-adrenergic receptor antagonist, phenoxybenzamine, an α2-adrenergic receptor antagonist, yohimbine, a ß-adrenergic receptor antagonist, propranolol, a mixed 5-HT1/5-HT2 serotonergic receptor antagonist, methysergide, a nonselective 5-HT2 serotonergic receptor antagonist, cyproheptadine, a nonselective muscarinic acetylcholine receptor antagonist, atropine, D2, D3, D4 dopamine receptor antagonist, haloperidol, a γ-aminobutyric acid subunit A (GABAA) receptor antagonist, bicuculline, naloxone, a nonselective opioid receptor antagonist and nitro-l-arginine, a nitric oxide synthase inhibitor. Kisspeptin-13 facilitated learning and memory consolidation in a passive avoidance paradigm. Phenoxybenzamine, yohimbine, propranolol, methysergide, cyproheptadine, atropine, bicuculline and nitro-l-arginine prevented the action of kisspeptin-13 on passive avoidance learning, but haloperidol and naloxone did not block the effects of kisspeptin-13. The results demonstrated that the action of kisspeptin-13 on the facilitation of passive avoidance learning and memory consolidation is mediated, at least in part, through interactions of the α2-adrenergic, beta-adrenergic, 5-HT2 serotonergic, muscarinic cholinergic and GABA-A-ergic receptor systems and nitric oxide.

Administration-time differences in effects of hypertension medications on ambulatory blood pressure regulation.

Specific features of the 24-h blood pressure (BP) pattern are linked to progressive injury of target tissues and risk of cardiovascular disease (CVD) events. Several studies have consistently shown an association between blunted asleep BP decline and risk of fatal and nonfatal CVD events. Thus, there is growing focus on ways to properly control BP during nighttime sleep as well as during daytime activity. One strategy, termed chronotherapy, entails the timing of hypertension medications to endogenous circadian rhythm determinants of the 24-h BP pattern. Significant and clinically meaningful treatment-time differences in the beneficial and/or adverse effects of at least six different classes of hypertension medications, and their combinations, are now known. Generally, calcium channel blockers (CCBs) are more effective with bedtime than morning dosing, and for dihydropyridine derivatives bedtime dosing significantly reduces risk of peripheral edema. The renin-angiotensin-aldosterone system is highly circadian rhythmic and activates during nighttime sleep. Accordingly, evening/bedtime ingestion of the angiotensin-converting enzyme inhibitors (ACEIs) benazepril, captopril, enalapril, lisinopril, perindopril, quinapril, ramipril, spirapril, trandolapril, and zofenopril exerts more marked effect on the asleep than awake systolic (SBP) and diastolic (DBP) BP means. Likewise, the bedtime, in comparison with morning, ingestion schedule of the angiotensin-II receptor blockers (ARBs irbesartan, olmesartan, telmisartan, and valsartan exerts greater therapeutic effect on asleep BP, plus significant increase in the sleep-time relative BP decline, with the additional benefit, independent of drug terminal half-life, of converting the 24-h BP profile into a more normal dipping pattern. This is the case also for the bedtime versus upon-awakening regimen of combination ARB-CCB, ACEI-CCB, and ARB-diuretic medications. The chronotherapy of conventional hypertension medications constitutes a new and cost-effective strategy for enhancing the control of daytime and nighttime SBP and DBP levels, normalizing the dipping status of their 24-h patterning, and potentially reducing the risk of CVD events and end-organ injury, for example, of the blood vessels and tissues of the heart, brain, kidney, and retina.

Nanosuspension based in situ gelling nasal spray of carvedilol: development, in vitro and in vivo characterization.

The objective of the present investigation was to develop in situ gelling nasal spray formulation of carvedilol (CRV) nanosuspension to improve the bioavailability and therapeutic efficiency. Solvent precipitation-ultrasonication method was opted for the preparation of CRV nanosuspension which further incorporated into the in situ gelling polymer phase. Optimized formulation was extensively characterized for various physical parameters like in situ gelation, rheological properties and in vitro drug release. Formation of in situ gel upon contact with nasal fluid was conferred via the use of ion-activated gellan gum as carrier. In vivo studies in rabbits were performed comparing the nasal bioavailability of CRV after oral, nasal, and intravenous administration. Optimized CRV nanosuspension prepared by combination of poloxamer 407 and oleic acid showed good particle size [d (0.9); 0.19 µm], zeta potential (+10.2 mV) and polydispersity (span; 0.63). The formulation containing 0.5% w/v gellan gum demonstrated good gelation ability and desired sustained drug release over period of 12 h. In vivo pharmacokinetic study revealed that the absolute bioavailability of in situ nasal spray formulation (69.38%) was significantly increased as compared to orally administered CRV (25.96%) with mean residence time 8.65 h. Hence, such in situ gel system containing drug nanosuspension is a promising approach for the intranasal delivery in order to increase nasal mucosal permeability and in vivo residence time which altogether improves drug bioavailability.

Administration of the cyclic peptide COR-1 in humans (phase I study): ex vivo measurements of anti-ß1-adrenergic receptor antibody neutralization and of immune parameters.

AIMS: A novel concept for the treatment of heart failure is the neutralization of antibodies against the ß(1)-adrenergic receptor (anti-ß(1)AR-ab). In a rat model of autoimmune cardiomyopathy, the cyclic peptide COR-1 (given i.v. once monthly) neutralized anti-ß(1)AR-abs and prevented anti-ß(1)AR-ab-induced myocardial damage, and completely reverted cardiac dysfunction over 3-6 months. METHODS AND RESULTS: A clinical phase I trial was designed as a single-blinded, placebo-controlled study. Fifty human volunteers received COR-1 or matching placebo as a single i.v. administration with ascending doses (10-240 mg). Primary endpoints were safety and tolerability, while the pharmacokinetic profile of COR-1 was assessed as a secondary endpoint. All five investigated dose groups were well tolerated; no drug-related side effects occurred. Pharmacokinetics revealed a favourable profile with an almost complete plasma clearance within 60 min after administration. Pharmacodynamic investigation showed dose-dependent efficacy with almost complete scavenging of pathological anti-ß(1)AR-abs ex vivo at the two highest doses. No anti-COR-1 autoantibodies occurred. No other effects on the immune system (such as an increase of crucial cytokines) were observed up to 43 days after drug administration, nor upon incubation of anti-ß(1)AR-ab-positive patient blood samples with COR-1 ex vivo. CONCLUSIONS: COR-1 was shown to be safe after i.v. administration in vivo; no relevant side effects occurred. Efficacy was estimated from ex vivo investigation of the potency to neutralize specific anti-ß(1)-AR-abs. TRIAL REGISTRATION: NCT 01043146, Eudra CT 2008-007745-31.

Study of the nature of sympathetic trunk nerve fibers enhancing gastric motility.

Stimulation of the sympathetic nerve in the thoracic cavity often does not inhibit, but increases stomach contractions in dogs. Blockade of α- and ß-adrenoceptors potentiates this stimulatory effect, while blockade of S(1,2)-receptors localized mainly in smooth muscle cells eliminates it. It is concluded that sympathetic nerve includes serotonergic fibers stimulating gastric motility.