Participation of the descending noradrenergic inhibitory system in the anti-hyperalgesic effect of acetaminophen in a rat model of inflammation

AIMS

This study investigated the relationship between the analgesic efficacy of acetaminophen and the descending noradrenergic systems using rodent models of inflammatory pain.

MAIN METHODS

Inflammatory pain models were established by carrageenan injection into rats' paws. The models were defined as acute (4 h after carrageenan injection), subacute (24 h after carrageenan injection), and late (1 week after carrageenan injection) phase. To evaluate intravenous acetaminophen treatment, the withdrawal threshold to mechanical stimuli was assessed simultaneously with in vivo microdialysis assay of noradrenaline levels in the locus coeruleus (LC). Further analyses were performed to observe the effect of yohimbine on the treatment and the impact of AM404 treatment, a metabolite of acetaminophen, on noradrenaline levels in the LC.

KEY FINDINGS

In all phases, intravenous acetaminophen had a significant anti-hyperalgesic effect (p < 0.05). There was a significant time-dependent increase in the noradrenaline concentration within the LC (acetaminophen versus saline treatment; at 30 min, p < 0.001; 60 min, p < 0.01) in the subacute pain model, but not in the acute and late phase pain models. Intrathecal pre-injection of yohimbine attenuated the anti-hyperalgesic effect after acetaminophen injection only in the subacute model (p < 0.05). In the subacute pain model, intracerebroventricular administration of AM404 showed the same trend in noradrenaline levels as acetaminophen administration (AM404 versus vehicle group at 30 min, p < 0.001).

SIGNIFICANCE

We found the descending noradrenergic inhibitory system is involved in the antinociceptive action of acetaminophen in the subacute phase of inflammatory pain.

Discriminative stimulus effects of 3,4-methylenedioxypyrovalerone (MDPV) and structurally related synthetic cathinones

The 3,4-methylenedioxypyrovalerone (MDPV), and other structurally related synthetic cathinones, are popular alternatives to prototypical illicit psychostimulants, such as cocaine and methamphetamine. These drugs are often referred to as 'bath salts' and function either as cocaine-like inhibitors of monoamine uptake, or amphetamine-like substrates for dopamine, norepinephrine and serotonin transporters. These studies used male Sprague-Dawley rats trained to discriminate MDPV from saline to evaluate the substitution profiles of structurally related synthetic cathinones, cocaine, and other direct-acting dopamine and noradrenergic receptor agonists in order to characterize the relative contributions of dopamine, norepinephrine and serotonin to the discriminative stimulus effects of MDPV. As expected, each of the cathinones and cocaine dose-dependently increased MDPV-appropriate responding, with a rank-order potency that was positively correlated with their potency to inhibit dopamine and norepinephrine, but not serotonin, a relationship that is consistent with the rank order to maintain self-administration. The dopamine D2/3 receptor-preferring agonist quinpirole produced a modest increase in MDPV-appropriate responding, whereas the dopamine D1/5 receptor agonist, SKF 82958, nonselective dopamine receptor agonist, apomorphine, as well as the α-1, and α-2 adrenergic receptor agonists, phenylephrine and clonidine, respectively, failed to increase MDPV-appropriate responding at doses smaller than those that suppressed responding altogether. Although these studies do not support a role for serotonergic or adrenergic systems in mediating/modulating the discriminative stimulus effects of MDPV, convergent evidence is provided to suggest that the discriminative stimulus effects of MDPV are primarily mediated by its capacity to inhibit dopamine uptake, and the subsequent activation of dopamine D2 or D3 receptors.

Central norepinephrine transmission is required for stress-induced repetitive behavior in two rodent models of obsessive-compulsive disorder

RATIONALE

Obsessive-compulsive disorder (OCD) is characterized by repetitive behaviors exacerbated by stress. Many OCD patients do not respond to available pharmacotherapies, but neurosurgical ablation of the anterior cingulate cortex (ACC) can provide symptomatic relief. Although the ACC receives noradrenergic innervation and expresses adrenergic receptors (ARs), the involvement of norepinephrine (NE) in OCD has not been investigated.

OBJECTIVE

To determine the effects of genetic or pharmacological disruption of NE neurotransmission on marble burying (MB) and nestlet shredding (NS), two animal models of OCD.

METHODS

We assessed NE-deficient (Dbh -/-) mice and NE-competent (Dbh +/-) controls in MB and NS tasks. We also measured the effects of anti-adrenergic drugs on NS and MB in control mice and the effects of pharmacological restoration of central NE in Dbh -/- mice. Finally, we compared c-fos induction in the locus coeruleus (LC) and ACC of Dbh -/- and control mice following both tasks.

RESULTS

Dbh -/- mice virtually lacked MB and NS behaviors seen in control mice but did not differ in the elevated zero maze (EZM) model of general anxiety-like behavior. Pharmacological restoration of central NE synthesis in Dbh -/- mice completely rescued NS behavior, while NS and MB were suppressed in control mice by anti-adrenergic drugs. Expression of c-fos in the ACC was attenuated in Dbh -/- mice after MB and NS.

CONCLUSION

These findings support a role for NE transmission to the ACC in the expression of stress-induced compulsive behaviors and suggest further evaluation of anti-adrenergic drugs for OCD is warranted.

Noradrenergic projections from the locus coeruleus to the amygdala constrain fear memory reconsolidation

Memory reconsolidation is a fundamental plasticity process in the brain that allows established memories to be changed or erased. However, certain boundary conditions limit the parameters under which memories can be made plastic. Strong memories do not destabilize, for instance, although why they are resilient is mostly unknown. Here, we investigated the hypothesis that specific modulatory signals shape memory formation into a state that is reconsolidation-resistant. We find that the activation of the noradrenaline-locus coeruleus system (NOR-LC) during strong fear memory encoding increases molecular mechanisms of stability at the expense of lability in the amygdala of rats. Preventing the NOR-LC from modulating strong fear encoding results in the formation of memories that can undergo reconsolidation within the amygdala and thus are vulnerable to post-reactivation interference. Thus, the memory strength boundary condition on reconsolidation is set at the time of encoding by the action of the NOR-LC.

[Discontinuation of SSRIs and SNRIs]

Interruption or abrupt discontinuation of the use of antidepressants may lead to withdrawal symptoms. These are most common with selective serotonin reuptake inhibitors (SSRIs) and serotonin-noradrenaline reuptake inhibitors (SNRIs).There is insufficient scientific evidence about the prevalence of antidepressant withdrawal symptoms and how to optimally discontinue antidepressants. The multidisciplinary document 'Discontinuation of SSRIs & SNRIs' offers a rationale and suggestions for the gradual tapering of these antidepressants. The following factors are consistently named as risk factors for the occurrence of withdrawal symptoms: (a) the patient experiences withdrawal symptoms in case of non-compliance or skipped doses; (b) a previous attempt to stop was unsuccessful; and (c) the patient is being treated with higher doses than the smallest effective dose of SSRIs or SNRIs. In patients with one or more risk factors, a tapering schedule with non-linear dose-reduction steps should be considered. The speed at which these steps are taken, should be adjusted depending on occurrence of withdrawal symptoms. Shared decision-making by patient and physician is the best way to select a tapering schedule.

Kava and its Kavalactones Inhibit Norepinephrine-induced Intracellular Calcium Influx in Lung Cancer Cells

Kava, the extract of the roots of Piper methysticum, has been traditionally consumed in the South Pacific islands for its natural relaxing property. Epidemiological data suggests that kava consumption may reduce human cancer risk, and in vitro and in vivo models suggest chemopreventive potential against carcinogen-induced tumorigenesis. Therefore, knowledge about its molecular mechanisms and responsible ingredient(s) for these beneficial properties will better guide kava's use for the management of these disorders. Psychological stress typically results in increased production of stress hormones, such as norepinephrine (NE), which activate adrenergic receptors (ARs). Psychological stress has also been associated with increased cancer incidence and poor clinical outcomes in cancer patients. Mechanistically, binding of NE to ARs induces intracellular calcium influx, which activates downstream signaling pathways involved in both stress and cancer development. In this study, we characterized the effect of kava and its components, 3 fractions and 6 major kavalactones, on NE-induced intracellular calcium influx in H1299, a human non-small cell lung carcinoma cell line. Results show that kava extract effectively inhibits NE-mediated intracellular calcium influx in H1299 cells, potentially through antagonizing β-AR signaling. This inhibitory activity is recapitulated by the major kavalactones in kava. Among the 6 major kavalactones, DHK demonstrated the best potency. Taken together, our study suggests a novel mechanism through which kava and its ingredients potentially offer the anxiolytic and cancer-preventive activity.

Activation of alpha-1 adrenergic receptors increases cytosolic calcium in neurones of the paraventricular nucleus of the hypothalamus

Norepinephrine (NE) activates adrenergic receptors (ARs) in the hypothalamic paraventricular nucleus (PVN) to increase excitatory currents, depolarise neurones and, ultimately, augment neuro-sympathetic and endocrine output. Such cellular events are known to potentiate intracellular calcium ([Ca²⁺ ]_i ); however, the role of NE with respect to modulating [Ca²⁺ ]_i in PVN neurones and the mechanisms by which this may occur remain unclear. We evaluated the effects of NE on [Ca²⁺ ]_i of acutely isolated PVN neurones using Fura-2 imaging. NE induced a slow increase in [Ca²⁺ ]_i compared to artificial cerebrospinal fluid vehicle. NE-induced Ca²⁺ elevations were mimicked by the α₁ -AR agonist phenylephrine (PE) but not by α₂ -AR agonist clonidine (CLON). NE and PE but not CLON also increased the overall number of neurones that increase [Ca²⁺ ]_i (ie, responders). Elimination of extracellular Ca²⁺ or intracellular endoplasmic reticulum Ca²⁺ stores abolished the increase in [Ca²⁺ ]_i and reduced responders. Blockade of voltage-dependent Ca²⁺ channels abolished the α₁ -AR induced increase in [Ca²⁺ ]_i and number of responders, as did inhibition of phospholipase C inhibitor, protein kinase C and inositol triphosphate receptors. Spontaneous phasic Ca²⁺ events, however, were not altered by NE, PE or CLON. Repeated K⁺ -induced membrane depolarisation produced repetitive [Ca²⁺ ]_i elevations. NE and PE increased baseline Ca²⁺ , whereas NE decreased the peak amplitude. CLON also decreased peak amplitude but did not affect baseline [Ca²⁺ ]_i . Taken together, these data suggest receptor-specific influence of α₁ and α₂ receptors on the various modes of calcium entry in PVN neurones. They further suggest Ca²⁺ increase via α₁ -ARs is co-dependent on extracellular Ca²⁺ influx and intracellular Ca²⁺ release, possibly via a phospholipase C inhibitor-mediated signalling cascade.

Effect of monoamine reuptake inhibition and α1 blockade on respiratory arrest and death following electroshock-induced seizures in mice

OBJECTIVE

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in patients with refractory epilepsy. Although the mechanisms for SUDEP are incompletely understood, seizure-induced respiratory arrest (S-IRA) has been strongly and consistently implicated. A body of evidence indicates that serotonin (5-HT), a modulator of breathing, plays a critical role in SUDEP. Because the 5-HT and norepinephrine (NE) systems interact in many biologic processes and NE is known to modulate breathing and seizures, we hypothesized that NE may play a role in S-IRA and SUDEP.

METHODS

We examined the effects of pharmacologic manipulation of 5-HT and NE on S-IRA and death following maximal electroshock (MES)-induced seizures in adult wild-type (WT) mice, genetically 5-HT neuron-deficient (Lmx1bf/f/p ) mice, and chemically NE neuron-deficient mice. Mice were treated with pharmacologic agents targeting the serotonergic and noradrenergic systems and subjected to seizure induction via MES while breathing was measured via whole-body plethysmography.

RESULTS

S-IRA and death was reduced in WT mice with NE reuptake inhibitors (NRIs), reboxetine and atomoxetine, selective serotonin reuptake inhibitors (SSRIs), fluoxetine and citalopram, and the dual 5-HT/NE reuptake inhibitor (SNRI), duloxetine. S-IRA and death was also reduced in Lmx1bf/f/p mice with reboxetine and fluoxetine. The protective effects of the reuptake inhibitors were prevented by the α1 antagonist, prazosin. Citalopram did not reduce S-IRA and death in NE neuron-deficient mice.

SIGNIFICANCE

These data suggest that 5-HT and NE critically interact in the modulation of breathing following a seizure and potentially inform preventive strategies for SUDEP.

Strategies to Treat Chronic Pain and Strengthen Impaired Descending Noradrenergic Inhibitory System

Gabapentinoids (gabapentin and pregabalin) and antidepressants (tricyclic antidepressants and serotonin noradrenaline reuptake inhibitors) are often used to treat chronic pain. The descending noradrenergic inhibitory system from the locus coeruleus (LC) to the dorsal horn of the spinal cord plays an important role in the analgesic mechanisms of these drugs. Gabapentinoids activate the LC by inhibiting the release of γ-aminobutyric acid (GABA) and inducing the release of glutamate, thereby increasing noradrenaline levels in the spinal cord. Antidepressants increase noradrenaline levels in the spinal cord by inhibiting reuptake, and accumulating noradrenaline inhibits chronic pain through α₂-adrenergic receptors in the spinal cord. Recent animal studies, however, revealed that the function of the descending noradrenergic inhibitory system is impaired in chronic pain states. Other recent studies found that histone deacetylase inhibitors and antidepressants restore the impaired noradrenergic descending inhibitory system acting on noradrenergic neurons in the LC.

Noradrenergic targets for the treatment of alcohol use disorder

The role of norepinephrine (NE) in the development of alcohol use disorder (AUD) has been studied over the past several decades. However, the NE system has been largely ignored for many years as a potential target for medication development for AUD. More recently, preclinical and clinical studies have demonstrated the potential value of targeting NE signaling for developing new pharmacological treatments for AUD. This review contributes to a special issue of Psychopharmacology focused on promising targets for alcohol addiction. Specifically, this review coalesces preclinical and clinical neuroscience that re-evaluate the noradrenergic system, and in particular the alpha-1 receptor, as a potential target for AUD.

Probiotics Affect One-Carbon Metabolites and Catecholamines in a Genetic Rat Model of Depression

SCOPE

Probiotics may influence one-carbon (C1) metabolism, neurotransmitters, liver function markers, or behavior.

METHODS AND RESULTS

Male adult Flinders Sensitive Line rats (model of depression, FSL; n = 22) received Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 (109 or 1010 colony-forming units per day) or vehicle for 10 weeks. The controls, Flinders Resistant Line rats (FRL, n = 8), only received vehicle. C1-related metabolites were measured in plasma, urine, and different tissues. Monoamine concentrations were measured in plasma, hippocampus, and prefrontal cortex. Vehicle-treated FSL rats had higher plasma concentrations of betaine, choline, and dimethylglycine, but lower plasma homocysteine and liver S-adenosylmethionine (SAM) than FRLs. FSL rats receiving high-dose probiotics had lower plasma betaine and higher liver SAM compared to vehicle-treated FSL rats. FSLs had higher concentrations of norepinephrine, dopamine, and serotonin than FRLs across various brain regions. Probiotics decreased plasma dopamine in FSLs in a dose-dependent manner. There were no detectable changes in liver function markers or behavior.

CONCLUSIONS

Probiotics reduced the flow of methyl groups via betaine, increased liver SAM, and decreased plasma dopamine and norepinephrine. Since these changes in methylation and catecholamine pathways are known to be involved in several diseases, future investigation of the effect of probiotics is warranted.

Interventional procedures and future drug therapy for hypertension

Hypertension management poses a major challenge to clinicians globally once non-drug (lifestyle) measures have failed to control blood pressure (BP). Although drug treatment strategies to lower BP are well described, poor control rates of hypertension, even in the first world, suggest that more needs to be done to surmount the problem. A major issue is non-adherence to antihypertensive drugs, which is caused in part by drug intolerance due to side effects. More effective antihypertensive drugs are therefore required which have excellent tolerability and safety profiles in addition to being efficacious. For those patients who either do not tolerate or wish to take medication for hypertension or in whom BP control is not attained despite multiple antihypertensives, a novel class of interventional procedures to manage hypertension has emerged. While most of these target various aspects of the sympathetic nervous system regulation of BP, an additional procedure is now available, which addresses mechanical aspects of the circulation. Most of these new devices are supported by early and encouraging evidence for both safety and efficacy, although it is clear that more rigorous randomized controlled trial data will be essential before any of the technologies can be adopted as a standard of care.

Involvement of alpha- and beta-adrenoceptors in the automaticity of the isolated guinea pig pulmonary vein myocardium

We examined the involvement of adrenoceptors in the automaticity of the pulmonary vein myocardium, which probably plays a crucial role in the generation of atrial fibrillation. The automatic activity of the myocardium in guinea pig pulmonary vein tissue preparations were monitored by contractile force or membrane potential measurement. In quiescent preparations, application of noradrenaline induced an automatic activity. The firing frequency was reduced by prazosin or atenolol. Methoxamine induced an automatic activity of low frequency, which was accelerated by further application of isoproterenol. In preparations driven at a constant frequency, noradrenaline, in the presence of atenolol, caused a depolarizing shift of the resting membrane potential and an increase in the slope of the diastolic depolarization. In contrast, in the presence of prazosin, noradrenaline had no effect on the slope, but caused acceleration of the late repolarization and a hyperpolarizing shift of the maximum diastolic potential. At clinically relevant concentrations, carvedilol significantly inhibited the noradrenaline-induced activity but bisoprolol did not. It was concluded that α₁- and β₁-adrenoceptor stimulation enhance automaticity through different mechanisms in the guinea pig pulmonary vein myocardium. Dual blockade of these adrenoceptors appears to be effective for suppressing noradrenaline-induced pulmonary vein automaticity and probably atrial fibrillation.

Presynaptic G Protein-Coupled Receptors Differentially Modulate Spontaneous Glutamate Release in the Supraoptic Nucleus

Spontaneous glutamate release in the supraoptic nucleus is modulated by a number of inhibitory G protein coupled receptors (GPCR), including GABAB , adenosine A1 and group III metabotropic glutamate receptors (mGluR). It remains unclear whether they have distinct roles or are redundant mechanisms that protect from hyperexcitation. To address this question, we facilitated spontaneous glutamate release using nifedipine or forskolin, which act in a protein kinase A (PKA)-independent and -dependent manner, respectively, and tested the effects of inhibitory GPCR agonists. We found that a GABAB receptor (GABAB R) agonist specifically inhibited forskolin-induced miniature excitatory postsynaptic currents (mEPSC), in contrast to an adenosine A1 receptor (A1R) agonist, which specifically inhibited nifedipine-induced mEPSCs. This suggests that GABAB Rs and A1 Rs modulate independent mechanisms activated by forskolin and nifedipine, respectively. However, the inhibitory effects of GABAB R and A1 R agonists on basal mEPSCs occluded each other, suggesting that these receptors also have an overlapping role. Group III mGluRs appear to have a greater control over glutamate release because agonists to these receptors inhibited both nifedipine- and forskolin-induced mEPSCs. mEPSCs induced by norepinephrine had the same characteristics as those induced by forskolin [i.e. PKA-dependence and sensitivity to GABAB R and group III mGluR agonists, but not an A1 R agonist]. In summary, the present study highlights the differential effects of GABAB R, A1 R and mGluR agonists on glutamate release stimulated by different secretagogues, including the endogenous neuromodulator norepinephrine. These results suggest that the roles of these inhibitory GPCRs are not completely redundant, and also indicate the physiological implications of having different excitatory and inhibitory GPCRs on the same synapse.

Impact of medications on mIBG uptake, with specific attention to the heart: Comprehensive review of the literature

BACKGROUND

A critical review of the literature on drug interactions with mIBG uptake was performed to allow formulation of contemporary guidance regarding withholding medications prior to clinical imaging studies.

METHODS

Published information was extracted on the experimental system used, the quantitative characteristics of the measurements, and whether any data directly examining cardiac tissues were included. Level of evidence for each medication category was assessed on a qualitative scale of very low, low, medium, or high. Strength of medication effect for inhibition of mIBG uptake was judged as none, weak, moderate, or strong.

RESULTS

The only medications for which level of evidence was judged high were labetalol and reserpine. Level of evidence was judged medium for tricyclic antidepressants, calcium channel blockers, and antiarrhythmics (specifically amiodarone). Evidence was judged sufficient to recommend withholding labetalol and the tricyclic antidepressants prior to mIBG cardiac imaging. Mechanistic evidence was sufficient to suggest consideration of withdrawal of sympathomimetic amines and serotonin-norepinephrine reuptake inhibitors (SNRIs).

CONCLUSIONS

As there is strong evidence for inhibition of mIBG uptake in only a small number of compounds, clinical decisions regarding withdrawal of concomitant medications should be individualized by considering the potential consequences of a false-positive (artificially low cardiac uptake) imaging result.

3-iodothyronamine differentially modulates α-2A-adrenergic receptor-mediated signaling

Most in vivo effects of 3-iodothyronamine (3-T1AM) have been thus far thought to be mediated by binding at the trace amine-associated receptor 1 (TAAR1). Inconsistently, the 3-T1AM-induced hypothermic effect still persists in Taar1 knockout mice, which suggests additional receptor targets. In support of this general assumption, it has previously been reported that 3-T1AM also binds to the α-2A-adrenergic receptor (ADRA2A), which modulates insulin secretion. However, the mechanism of this effect remains unclear. We tested two different scenarios that may explain the effect: the sole action of 3-T1AM at ADRA2A and a combined action of 3-T1AM at ADRA2A and TAAR1, which is also expressed in pancreatic islets. We first investigated a potential general signaling modification using the label-free EPIC technology and then specified changes in signaling by cAMP inhibition and MAPKs (ERK1/2) determination. We found that 3-T1AM induced Gi/o activation at ADRA2A and reduced the norepinephrine (NorEpi)-induced MAPK activation. Interestingly, in ADRA2A/TAAR1 hetero-oligomers, application of NorEpi resulted in uncoupling of the Gi/o signaling pathway, but it did not affect MAPK activation. However, 3-T1AM application in mice over a period of 6 days at a daily dose of 5 mg/kg had no significant effects on glucose homeostasis. In summary, we report an agonistic effect of 3-T1AM on the ADRA2A-mediated Gi/o pathway but an antagonistic effect on MAPK induced by NorEpi. Moreover, in ADRA2A/TAAR1 hetero-oligomers, the capacity of NorEpi to stimulate Gi/o signaling is reduced by co-stimulation with 3-T1AM. The present study therefore points to a complex spectrum of signaling modification mediated by 3-T1AM at different G protein-coupled receptors.

α2-Adrenoceptors in the treatment of major neuropsychiatric disorders

Presynaptic autoreceptors mediate a retrograde transfer of information by a negative feedback mechanism mediated by the transmitter of the neuron, and fulfill an autoregulatory function in neurotransmission in the peripheral and central nervous system (CNS). Starting with norepinephrine (NE), it was later reported that an autoreceptor-mediated negative feedback mechanism exists for other neurotransmitters, including dopamine (DA), serotonin, acetylcholine, histamine, GABA, and glutamate. This feedback mechanism regulates calcium-dependent transmitter release and synthesis through terminal presynaptic autoreceptors, while the firing rate of the neuron is regulated through somatodendritic autoreceptors.

Vascular effects of diphenylmethoxypiperidine-derived dopamine uptake inhibitors

Vascular effects of 4-aryl methoxypiperidinol compounds previously shown to share with cocaine the ability to inhibit the dopamine transporter are described. All the compounds tested inhibit KCl-induced and noradrenaline-dependent contractions in mesenteric arteries ex vivo. Thus, diphenylpyraline and its analogs may have a role as therapeutic options for the treatment of some of the cardiotoxic effects of cocaine intoxications.

Reactive oxygen species are physiological mediators of the noradrenergic signaling pathway in the mouse supraoptic nucleus

Free radicals are essential for the vasopressin (AVP) response to plasmatic hyperosmolarity. Noradrenergic afferents are the major projections on the supraoptic nucleus (SON) of the hypothalamus and stimulate the expression of AVP via a nitric oxide (NO) pathway. In this study, we investigated the mechanisms linking free radicals and noradrenaline (NA)-induced regulation of AVP. Analysis of Tg8 transgenic mice, invalidated for the monoamine oxidase-A gene and with consequently high levels of brain monoamines and AVP in the SON, showed that free radicals are more abundant in their SON than in that of wild-type mice (WT). Antioxidant superoxide dismutase 1 and 2 and catalase enzyme activities were also higher in these mice than in WT. This may explain the observed absence of cytotoxicity that would otherwise be associated with such high level of free radicals. Treatment of Tg8 mice with α-MPT, a blocking agent for NA synthesis, decreased both the production of free radicals and the AVP levels in the SON. Furthermore, incubation of ex vivo slices including the SON with NA increased the production of free radicals and AVP levels in wild-type mice. When NA was associated with α-lipoic acid, an antioxidant blocking the production of free radicals, AVP remained at its control level, indicating that free radicals are required for the effect of NA on the expression of AVP. In slices incubated with SNP, a producer of NO, free radicals and AVP levels increased. When NA was associated with L-NAME (a NO synthase blocker), the levels of free radicals and AVP were the same as in controls. Thus, the noradrenaline-NO pathway, which stimulates the expression of vasopressin, involves free radicals. This study provides further evidence of the physiological importance of free radicals, which should no longer be considered solely as cytotoxic factors.

Designer receptor manipulations reveal a role of the locus coeruleus noradrenergic system in isoflurane general anesthesia

Mechanisms driving emergence from general anesthesia are not well understood. The noradrenergic brain nucleus locus coeruleus (LC) modulates arousal and may have effects on general anesthetic state. Using virally delivered designer receptors to specifically control LC norepinephrine (NE) neurons, we investigated the causal relationship between LC-NE activity and general anesthetic state under isoflurane. Selective activation of LC-NE neurons produced cortical electroencephalography (EEG) activation under continuous deep isoflurane anesthesia. Specifically, LC-NE activation reduced burst suppression in EEG and drove a rightward shift in peak EEG frequency with reduced δ EEG power and increased θ EEG power, measures of cortical arousal. LC-NE activation also accelerated behavioral emergence from deep isoflurane anesthesia; this was prevented with β or α1 noradrenergic antagonists. Moreover, these adrenoreceptor antagonists alone were sufficient to markedly potentiate anesthetic duration when delivered centrally or peripherally. Induction of anesthesia also was retarded by LC-NE activation. Our results demonstrate that the LC-NE system strongly modulates the anesthetic state, and that changes in LC-NE neurotransmission alone can affect the emergence from isoflurane general anesthesia. Taken together, these findings extend our understanding of mechanisms underlying general anesthesia and cortical arousal, and have significant implications for optimizing the clinical safety and management of general anesthesia.

Comparative assessment of adherence measures and resource use in SSRI/SNRI-treated patients with depression using second-generation antipsychotics or L-methylfolate as adjunctive therapy

BACKGROUND

Antidepressant monotherapy is effective in achieving treatment remission in only approximately one third of patients with depression, and even switching to a second antidepressant brings the cumulative remission rate to only 50%-55%. This has led to an interest in augmentation therapy for the management of treatment-resistant depression.

OBJECTIVES

To assess (a) selective serotonin reuptake inhibitor/selective norepinephrine reuptake inhibitor (SSRI/SNRI) adherence when augmented with second-generation atypical antipsychotics (SGAs) or L-methylfolate using a modified application of the Healthcare Effectiveness Data and Information Set (HEDIS) acute medication management (AMM) measures at the time of augmentation, and (b) the depression-specific and total health care cost, comparing the 2 forms of augmentation therapy in the treatment of depressive disorder.

METHODS

Patients with a diagnosis of depression and a pharmacy claim for an SSRI/SNRI between January 1, 2006, and December 31, 2009 (index date), and receiving concomitant augmentation therapy with either an SGA or L-methylfolate (augmentation date), were identified in the MarketScan database and followed for 231 days (follow-up). Patients were excluded for having any pharmacy claim for an antidepressant or SGA 90 days pre-index; having an L-methylfolate claim 6 months pre-index; age < 18 years on the index date; or a diagnosis of pregnancy, dementia, psychotic-related mental disorders, Alzheimer's disease, or Parkinson's disease in the 12-month pre-index period. Propensity score matching (3:1 ratio, atypical antipsychotic to L-methylfolate) was used to select the final study cohorts, using covariates of age, gender, comorbidities, index SSRI/SNRI, and index SSRI/SNRI dose. Adherence to antidepressant therapy was measured from the augmentation date and included a modified application of the HEDIS (mHEDIS) AMM acute and chronic phase measures as well as the 6-month medication possession ratio. Health care utilization and cost were measured for the 6-month postaugmentation period and included both total as well as depression-related utilization/cost. Comparisons between the closely matched SGA and L-methylfolate-augmented cohorts were made using chi-square tests for binary measures and t-tests for continuous measures.

RESULTS

Following propensity score matching, 4,053 SGA and 1,351 L-methylfolate patients were found to have augmentation of the index SSRI/SNRI within 12 months of the index date. The comparison groups were well matched on age, gender, comorbidities, and the type and dose of the SSRI/SNRI being augmented. The most common antidepressants augmented in both groups were escitalopram, duloxetine, and venlafaxine. Mean (standard deviation [SD]) time from index to augmentation was 73.5 [96.7] days for SGA and 105.9 [108.7] days for L-methylfolate (P < 0.001). The most common SGAs utilized for augmentation were quetiapine, aripiprazole, and risperidone. L-methylfolate was primarily dosed at 7.5 mg/day. The mHEDIS AMM acute phase measure was met by 68.7% of the SGA cohort and 78.7% of the L-methylfolate cohort (P < 0.001). The mHEDIS continuation phase measure was met by 50.3% of the SGA cohort and 62.1% of the L-methylfolate cohort (P < 0.001) following augmentation. Medical utilization (inpatient, emergency department, and outpatient) was significantly higher for the SGA group, while total prescription utilization was significantly higher in the L-methylfolate group. Mean [SD] total 6-month postaugmentation costs for the SGA group was $8,499 [$13,585] and $7,371 [$12,404] for the L-methylfolate group (P = 0.005), and 6-month depression-related costs were $2,688 [$4,201] for the SGA group and $1,613 [$2,315] for the L-methylfolate group (P < 0.001).

CONCLUSIONS

Patients who augmented SSRI/SNRI therapy with SGA or L-methylfolate achieved mHEDIS AMM acute phase and continuation phase adherence scores of 69%-79% and 50%-62%, respectively. These modified scores exceeded the 2012 national median benchmarks for unmodified HEDIS AMM measures for commercial health plans. In this study, augmentation with L-methylfolate was associated with significantly higher adherence measures compared with augmentation with SGA. In addition, health care utilization and total health care costs, as well as depression-related costs, were significantly lower in the L-methylfolate augmentation group compared with augmentation with SGA.

Additional antiepileptic mechanisms of levetiracetam in lithium-pilocarpine treated rats

Several studies have addressed the antiepileptic mechanisms of levetiracetam (LEV); however, its effect on catecholamines and the inflammatory mediators that play a role in epilepsy remain elusive. In the current work, lithium (Li) pretreated animals were administered LEV (500 mg/kg i.p) 30 min before the induction of convulsions by pilocarpine (PIL). Li-PIL-induced seizures were accompanied by increased levels of hippocampal prostaglandin (PG) E₂, myeloperoxidase (MPO), tumor necrosis factor-α, and interleukin-10. Moreover, it markedly elevated hippocampal lipid peroxides and nitric oxide levels, while it inhibited the glutathione content. Li-PIL also reduced hippocampal noradrenaline, as well as dopamine contents. Pretreatment with LEV protected against Li-PIL-induced seizures, where it suppressed the severity and delayed the onset of seizures in Li-PIL treated rats. Moreover, LEV reduced PGE₂ and MPO, yet it did not affect the level of both cytokines in the hippocampus. LEV also normalized hippocampal noradrenaline, dopamine, glutathione, lipid peroxides, and nitric oxide contents. In conclusion, alongside its antioxidant property, LEV anticonvulsive effect involves catecholamines restoration, as well as inhibition of PGE₂, MPO, and nitric oxide.

Coadministration of low-dose serotonin/noradrenaline reuptake inhibitor (SNRI) duloxetine with α 2-adrenoceptor blockers to treat both female and male mild-to-moderate stress urinary incontinence (SUI)

BACKGROUND

Female urinary incontinence is a relatively common disorder affecting women in different age groups, with significant prevalence amounts of stress-related subtype (stress urinary incontinence, SUI). Various neurotransmitters/neuromodulators - particularly both the glutamatergic and GABA-ergic ones - are involved in micturition/urinary continence nerve centre-based control, where Onuf's nucleus plays an important functional role under the adiuvant serotoninergic/ noradrenergic influences.

OBJECTIVES

To outline, deriving them from the literature review, the SUI therapeutic implications of SNRI (serotonin-noradrenaline reuptake inhibitors) particularly of the duloxetine, though displaying its full therapeutic dose (40 mg twice/day)-related side effects and, therefore, highlighting recent issues concerning novel drug administration modalities to avoid such adverse events. EMERGING KNOWLEDGES: Intriguing studies in SUI animal models have shown that co-administration of duloxetine low dose with α 2-adrenoceptor antagonists - given the α 2-adrenoceptor inhibition-induced enhancement of duloxetine effectiveness on the urethral rhabdospincter-can avoid the duloxetine-related adverse events though perspectively reaching, in perspective translational clinical applications, the awaited beneficial effects for women suffering from intrinsic rhabdosphincter deficiency-based mild-to-moderate SUI as well as, in men, to treat post-prostatectomy mild SUI.

Long acting propranolol and HSP-70 rich tumor lysate reduce tumor growth and enhance immune response against fibrosarcoma in Balb/c mice

BACKGROUND

Noradrenaline (NA), the principal neurotransmitter released from sympathetic nerve terminals, influences T-cell maturation, not only directly in developing T cells, but also indirectly, by acting on the thymic nonlymphoid cells. In vitro and in vivo studies have demonstrated the anti-proliferative, anti-migratory, anti-angiogenic and cytotoxic properties of propranolol, β-AR blocker, against various cancers.

OBJECTIVES

To evaluate the effect of propranolol on efficacy of HSP-70 rich lysate vaccine in immunotherapy of fibrosarcoma.

METHODS

Mouse fibrosarcoma WEHI-164 cells were used to immunize tumor-bearing mice with or without propranolol and HSP-70. Splenocytes proliferation, cytotoxicity activity of the splenocytes, naturally occurring CD4+ CD25high T-reg cells and IFN-γ and IL-4 secretion as well as tumor size, were assessed to describe the anti-tumor immune response.

RESULTS

A significant increase in the level of IFN-γ in the mice vaccinated with WEHI-164 cells enriched with HSP-70 and co-treated with propranolol was observed compared to controls. However, HSP enrichment or propranolol treatment alone did not enhance the immune response as measured by the level of IFN-γ. Likewise, a decrease in tumor growth in the test group (p<0.01) and a significant increase in CTL activity (p<0.05) was observed.

CONCLUSION

HSP enriched vaccine shows anti-tumor activity, probably due to the modulation of immune responses.

Antidepressant abietane diterpenoids from Chinese eaglewood

Ten new abietane diterpenoids, aquilarabietic acids A-J (1-10), and a new podocarpane diterpenoid, aquilarabietic acid K (11), were isolated from the petroleum ether and ethanol extracts of Chinese eaglewood. Among them, 3, 9, and 10 are artifacts. Their structures were established on the basis of data from extensive spectroscopic and X-ray diffraction analyses. Bioassay results indicated that 1 at 10 μM demonstrated remarkable antidepressant activity in vitro by inhibiting norepinephrine reuptake in rat brain synaptosomes by 81.4% and with an IC(50) value of 9.1 × 10(-7) M.

Simultaneous blockade of dopamine and noradrenaline reuptake promotes disadvantageous decision making in a rat gambling task

RATIONALE

The inability to make profitable long-term decisions has been implicated in several psychiatric disorders. There is emerging evidence to support a role for dopamine (DA) in decision making, but our understanding of the role of noradrenaline (NA) and serotonin (5-HT) in decision making, and of possible interactions between the three monoamines, is limited. Moreover, impulsivity has been associated with aberrant decision making, but the underlying mechanisms are incompletely understood.

OBJECTIVE

The purpose of this study is to improve our understanding of the neuropharmacological mechanisms of decision making and impulse control.

METHODS

We investigated the effects of amphetamine (0.25-1.0 mg/kg) and selective reuptake inhibitors of DA (GBR12909; 2.5-10 mg/kg), NA (atomoxetine; 0.3-3.0 mg/kg), and 5-HT (citalopram; 0.3-3.0 mg/kg) in a rat gambling task (rGT). Since the rGT allows for detection of impulsive action, i.e., premature responding, we also assessed the relationship between decision making and impulsivity.

RESULTS

In the rGT, rats developed an optimal choice strategy from the first session onwards. Elevation of endogenous DA or NA levels increased and decreased impulsivity, respectively, but did not alter decision making. However, simultaneous blockade of DA and NA disrupted decision making, reflected by a relative decrease in choice for the advantageous choice options. Increasing 5-HT neurotransmission did not affect decision making or impulsivity.

CONCLUSIONS

These data suggest important but complementary or redundant roles of DA and NA neurotransmission in decision-making processes based on reward probability and punishment. Moreover, impulse control and decision making in the rGT rely on dissociable mechanisms.

High-fat diet-induced alterations in the feeding suppression of low-dose nisoxetine, a selective norepinephrine reuptake inhibitor

Central noradrenergic pathways are involved in feeding and cardiovascular control, physiological processes altered by obesity. The present studies determined how high-fat feeding and body weight gain alter the sensitivity to the feeding suppression and neural activation to a selective norepinephrine reuptake inhibitor, nisoxetine. Acute administration of nisoxetine (saline: 0, 3, 10, and 30 mg/kg; i.p.) resulted in a dose-dependent reduction in the 24 h refeeding response in male Sprague Dawley rats maintained on standard chow. In a similar fashion, nisoxetine resulted in reductions in blood pressure and a compensatory increase in heart rate. From these studies, the 3 mg/kg dose was subthreshold. In a separate experiment, however, 10 wk exposure to a high-fat diet (60% fat) resulted in weight gain and significant feeding suppression following administration of nisoxetine (3 mg/kg) compared with animals fed a control diet (10% fat). Nisoxetine (3 mg/kg) also resulted in greater neural activation, as measured by c-Fos immunohistochemistry, in the arcuate nucleus of the hypothalamus in animals exposed to the high-fat diet. Such data indicate acute nisoxetine doses that suppress food intake can impact cardiovascular measures. It also suggests that the feeding suppression to a low-dose nisoxetine is enhanced as a result of high-fat diet and weight gain.

Chronic exposure to stress hormones promotes transformation and tumorigenicity of 3T3 mouse fibroblasts

Epinephrine and norepinephrine are produced during psychological stress and can directly bind to cells to induce DNA damage. These effects may have more long-lasting consequences such as DNA mutations resulting in an increased potential for cellular transformation and/or tumor progression. This study examined the molecular effects of a chronic (24 h) in vitro exposure to these stress hormones on murine 3T3 cells. Long exposures (24 h) in dose-response experiments with norepinephrine or epinephrine induced significant increases in DNA damage in treated cells compared to that of untreated controls as measured by the alkaline comet assay. Pre-treatment with a blocking agent (the β-adrenergic receptor antagonist propranolol) eliminated this increase in damage. In addition, both norepinephrine and epinephrine increased cellular transformation, as assessed by growth in soft agar, and 3T3 cells pre-treated with either norepinephrine or epinephrine induced a more rapid onset of tumors and more aggressive tumor growth in nude mice. In summary, incubation of 3T3 cells with catecholamines results in long-term DNA damage as measured by increased transformed phenotypes and tumor progression, indicating that they are important mediators of stress effects on genomic instability and vulnerability to tumor formation.

Bloating in gastroparesis: severity, impact, and associated factors

OBJECTIVES

Bloating is commonly reported in gastroparesis, but its prevalence, impact, and associated factors are uninvestigated. We aimed to quantify the prevalence of bloating in gastroparesis and relate its severity to clinical factors and quality of life.

METHODS

Survey, examination, and scintigraphy data were compared in 335 gastroparesis patients from 6 centers of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Gastroparesis Clinical Research Consortium. Bloating severity was stratified using Gastroparesis Cardinal Symptom Index (GCSI) bloating subscale scores.

RESULTS

Bloating severity of at least mild (GCSI ≥2) and severe (GCSI ≥4) grades were reported by 76 and 41% of patients, respectively. Bloating severity related to female gender (P<0.0001) and overweight status (P=0.04) on regression analysis and correlated with intensity of nausea, postprandial fullness, visible distention, abdominal pain, and altered bowel function (P<0.05). Disease etiology, smoking status, and gastric emptying did not relate to bloating subset (P>0.05). Disease-specific quality of life and general measures of well-being were progressively impaired with increasing bloating severity (P=0.01). Probiotic use (P=0.03) and use of antidepressants with significant norepinephrine reuptake inhibitor activity (P=0.045) use related to bloating severity; antiemetic use trended higher with worsening bloating (P=0.06).

CONCLUSIONS

Bloating is prevalent in gastroparesis and is severe in many individuals. Bloating severity relates to female gender, body weight, and intensity of other symptoms. The symptom impairs quality of life but is not influenced by gastric emptying rates. Antiemetics, probiotics, and antidepressants with significant norepinephrine reuptake inhibitor activity may affect reports of bloating. These findings provide insight into this underappreciated symptom of gastroparesis.

Oxytocin and dopamine stimulate ghrelin secretion by the ghrelin-producing cell line, MGN3-1 in vitro

To understand the physiological role of ghrelin, it is crucial to study both the actions of ghrelin and the regulation of ghrelin secretion. Although ghrelin actions have been extensively revealed, the direct factors regulating ghrelin secretion by ghrelin-producing cells (X/A-like cells), however, is not fully understood. In this study, we examined the effects of peptide hormones and neurotransmitters on in vitro ghrelin secretion by the recently developed ghrelin-producing cell line MGN3-1. Oxytocin and vasopressin significantly stimulated ghrelin secretion by MGN3-1 cells. Because MGN3-1 cells express only oxytocin receptor mRNA, not vasopressin receptor mRNA, oxytocin is the likely regulator, with the effect of vasopressin mediated by a cross-reaction. We also discovered that dopamine stimulates ghrelin secretion from MGN3-1 cells in a similar manner to the previously known ghrelin stimulators, epinephrine and norepinephrine. MGN3-1 cells expressed mRNA encoding dopamine receptors D1a and D2. The dopamine receptor D1 agonist fenoldopam stimulated ghrelin secretion, whereas the D2, D3 agonist bromocriptine did not. Furthermore, the D1 receptor antagonist SKF83566 attenuated the stimulatory effect of dopamine. These results indicate that the stimulatory effect of dopamine on ghrelin secretion is mediated by the D1a receptor. In conclusion, we identified two direct regulators of ghrelin, oxytocin and dopamine. These findings will provide new direction for further studies seeking to further understand the regulation of ghrelin secretion, which will in turn lead to greater understanding of the physiological role of ghrelin.

In vitro pharmacodynamic profile of Loranthus ferrugineus: evidence for noncompetitive antagonism of norepinephrine-induced vascular contraction

The mode by which Loranthus ferrugineus methanol extract antagonizes and/or modulates norepinephrine-induced vasoconstriction was investigated in rat aortic rings. The vascular effects of three different concentrations of this extract were challenged against cumulative additions of norepinephrine. Phentolamine, a nonselective α-adrenoceptor antagonist, verapamil, an L-type calcium channel blocker, and papaverine, a phosphodiesterase inhibitor, were used in three different concentrations as positive controls. Log concentration-response curves and double-reciprocal plots were constructed for the extract and each vasorelaxant. To characterize antagonism reversibility, the norepinephrine maximum contractile effect was examined before extract addition to the aortic ring chamber and after its removal. Phentolamine shifted the norepinephrine log concentration-response curve to the right with no significant depression in the maximum response. Similar to verapamil and papaverine, the extract produced a rightward shift in norepinephrine log concentration-response curve and a significant drop in maximum response. The double-reciprocal plots showed comparable y-intercept values for all phentolamine concentrations, a characteristic of competitive antagonism. In contrast, different y-intercept values on double-reciprocal plots were obtained for each concentration of extract, verapamil, and papaverine, typical of noncompetitive antagonism. The norepinephrine maximum contractile response was approximately similar before the addition of extract and after its removal. The data collectively showed that L. ferrugineus methanol extract exerted its vascular effect by reversible noncompetitive antagonism of norepinephrine-induced vasoconstriction. These findings add to the understanding of the cardiovascular mechanisms by which L. ferrugineus, a plant traditionally used for the management of hypertension, elicits its action.

Non-hormonal interventions for hot flushes in women with a history of breast cancer

BACKGROUND

Hot flushes are common in women with a history of breast cancer. Hormonal therapies are known to reduce these symptoms but are not recommended in women with a history of breast cancer due to their potential adverse effects. The efficacy of non-hormonal therapies is still uncertain.

OBJECTIVES

To assess the efficacy of non-hormonal therapies in reducing hot flushes in women with a history of breast cancer.

SEARCH STRATEGY

We searched the Cochrane Breast Cancer Group Specialised Register, CENTRAL (The Cochrane Library), MEDLINE, EMBASE, LILACS, CINAHL, PsycINFO (August 2008) and WHO ICTRP Search Portal. We handsearched reference lists of reviews and included articles, reviewed conference proceedings and contacted experts.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing non-hormonal therapies with placebo or no therapy for reducing hot flushes in women with a history of breast cancer.

DATA COLLECTION AND ANALYSIS

Two authors independently selected potentially relevant studies, decided upon their inclusion and extracted data on participant characteristics, interventions, outcomes and the risk of bias of included studies.

MAIN RESULTS

Sixteen RCTs met our inclusion criteria. We included six studies on selective serotonin (SSRI) and serotonin-norepinephrine (SNRI) reuptake inhibitors, two on clonidine, one on gabapentin, two each on relaxation therapy and homeopathy, and one each on vitamin E, magnetic devices and acupuncture. The risk of bias of most studies was rated as low or moderate. Data on continuous outcomes were presented inconsistently among studies, which precluded the possibility of pooling the results. Three pharmacological treatments (SSRIs and SNRIs, clonidine and gabapentin) reduced the number and severity of hot flushes. One study assessing vitamin E did not show any beneficial effect. One of two studies on relaxation therapy showed a significant benefit. None of the other non-pharmacological therapies had a significant benefit. Side-effects were inconsistently reported.

AUTHORS' CONCLUSIONS

Clonidine, SSRIs and SNRIs, gabapentin and relaxation therapy showed a mild to moderate effect on reducing hot flushes in women with a history of breast cancer.

Best practice guide for the treatment of nightmare disorder in adults

Prazosin is recommended for treatment of Posttraumatic Stress Disorder (PTSD)-associated nightmares. Level A. Image Rehearsal Therapy (IRT) is recommended for treatment of nightmare disorder. Level A. Systematic Desensitization and Progressive Deep Muscle Relaxation training are suggested for treatment of idiopathic nightmares. Level B. Venlafaxine is not suggested for treatment of PTSD-associated nightmares. Level B. Clonidine may be considered for treatment of PTSD-associated nightmares. Level C. The following medications may be considered for treatment of PTSD-associated nightmares, but the data are low grade and sparse: trazodone, atypical antipsychotic medications, topiramate, low dose cortisol, fluvoxamine, triazolam and nitrazepam, phenelzine, gabapentin, cyproheptadine, and tricyclic antidepressants. Nefazodone is not recommended as first line therapy for nightmare disorder because of the increased risk of hepatotoxicity. Level C. The following behavioral therapies may be considered for treatment of PTSD-associated nightmares based on low-grade evidence: Exposure, Relaxation, and Rescripting Therapy (ERRT); Sleep Dynamic Therapy; Hypnosis; Eye-Movement Desensitization and Reprocessing (EMDR); and the Testimony Method. Level C. The following behavioral therapies may be considered for treatment of nightmare disorder based on low-grade evidence: Lucid Dreaming Therapy and Self-Exposure Therapy. Level C No recommendation is made regarding clonazepam and individual psychotherapy because of sparse data.

Chronic exposure to elevated norepinephrine suppresses insulin secretion in fetal sheep with placental insufficiency and intrauterine growth restriction

In this study, we examined chronic norepinephrine suppression of insulin secretion in sheep fetuses with placental insufficiency-induced intrauterine growth restriction (IUGR). Glucose-stimulated insulin secretion (GSIS) was measured with a square-wave hyperglycemic clamp in the presence or absence of adrenergic receptor antagonists phentolamine (alpha) and propranolol (beta). IUGR fetuses were hypoglycemic and hypoxemic and had lower GSIS responsiveness (P < or = 0.05) than control fetuses. IUGR fetuses also had elevated plasma norepinephrine (3,264 +/- 614 vs. 570 +/- 86 pg/ml; P < or = 0.05) and epinephrine (164 +/- 32 vs. 60 +/- 12 pg/ml; P < or = 0.05) concentrations. In control fetuses, adrenergic inhibition increased baseline plasma insulin concentrations (1.7-fold, P < or = 0.05), whereas during hyperglycemia insulin was not different. A greater (P < or = 0.05) response to adrenergic inhibition was found in IUGR fetuses, and the average plasma insulin concentrations increased 4.9-fold at baseline and 7.1-fold with hyperglycemia. Unlike controls, basal plasma glucose concentrations fell (P < or = 0.05) with adrenergic antagonists. GSIS responsiveness, measured by the change in insulin, was higher (8.9-fold, P < or = 0.05) in IUGR fetuses with adrenergic inhibition than controls (1.8-fold, not significant), showing that norepinephrine suppresses insulin secretion in IUGR fetuses. Strikingly, in IUGR fetuses, adrenergic inhibition resulted in a greater GSIS responsiveness, because beta-cell mass was 56% lower and the maximal stimulatory insulin response tended (P < 0.1) to be higher than controls. This persistent norepinephrine suppression appears to be partially explained by higher mRNA concentrations of adrenergic receptors alpha(1D), alpha(2A), and alpha(2B) in a cohort of fetuses that were naïve to the antagonists. Therefore, norepinephrine suppression of insulin secretion was maintained, in part, by upregulating adrenergic receptor expression, but the beta-cells also appeared to compensate with enhanced GSIS. These findings may begin to explain why IUGR infants have a propensity for increased glucose requirements if norepinephrine is suddenly decreased after birth.

Norepinephrine-Induced Pulmonary Petechiae in the Rat: An Experimental Model with Potential Implications for Sudden Infant Death Syndrome

Autonomic nervous system abnormalities have been implicated in infants dying of or considered at high risk of sudden infant death syndrome (SIDS). In a rat model, norepinephrine (0.02 mg/kg) caused systemic hypertension and numerous pulmonary petechiae, the latter a common finding in SIDS. Petechiae were not seen below the diaphragm. The animals were killed by tracheal occlusion 5 min after the intravenous administration of norepinephrine. The number of pulmonary petechiae was greatly reduced by alpha-adrenergic blockade (phentolamine) and dopaminergic blockade (haloperidol) but not by beta-adrenergic blockade (timolol). A significantly greater reduction of peak mean systemic arterial pressure occurred after alpha-adrenergic blockade than with other blocking agents. It is conceivable that hypoxia-induced endogenous catecholamine release contributes to the pathogenesis of pulmonary petechiae found at necropsy of SIDS victims.

[Phentolamine antagonizes the effects of norepinephrine on the activity of pain-related neurons in the parafascicular nucleus of morphine-dependent rats]

OBJECTIVE

To examine the antagonization of phentolamine against the effects of norepinephrine (NE) on the activity of pain-related neurons in the parafascicular nucleus of morphine-dependent rats.

METHODS

Electric impulses were applied as nociceptive stimulus to the right sciatic nerve of morphine-dependent rats, and the discharges of the pain-related neurons in the parafascicular nucleus were recorded by extracellular recording method with glass microelectrodes.

RESULTS

Intracerebroventricular injection of norepinephrine resulted in the inhibition of evoked response of the pain-excited neurons as well as the excitation of evoked response of the pain-inhibiting neurons. Both the inhibitory effect on the electric discharges of the pain-excited neurons and the excitatory effect on the pain-inhibiting neurons of norepinephrine were almost completely blocked by intracerebroventricular administration of phentolamine.

CONCLUSION

Phentolamine antagonizes the inhibitory effect of norepinephrine on the activity of pain-related neurons in the parafascicular nucleus in morphine-dependent rats, and norepinephrine may play an important role in the integration of the pain signal through the alpha-receptors.

Patient-perceived anxiety levels associated with use of selective serotonin and serotonin norepinephrine reuptake inhibitors

Dental practitioners are sometimes reluctant to treat patients who are on psychopharmacological agents, due perhaps to the belief that these patients will be difficult to deal with. However patients whose medical history indicates emotional and psychiatric disorders and who are being treated with SSRI or SSNRI agents may actually present a more positive and more receptive attitude to treatment than what was sometimes previously encountered in these same individuals.

Cardiovascular responses to noradrenaline microinjection in the ventrolateral periaqueductal gray of unanesthetized rats

The periaqueductal gray area (PAG) is a mesencephalic area involved in cardiovascular modulation. Noradrenaline (NA), a neurotransmitter involved in central blood pressure control, is present in the rat PAG. We report here on the cardiovascular effects caused by NA microinjection into the ventrolateral PAG (vlPAG) of unanesthetized rats and the peripheral mechanism involved in their mediation. NA microinjection in the vlPAG of unanesthetized rats evoked dose-related pressor and bradycardiac responses. No significant cardiovascular responses were observed in urethane-anesthetized rats. The pressor response was potentiated by pretreatment with the ganglion blocker pentolinium (5 or 10 mg/kg, intravenously). Pretreatment with the vasopressin antagonist dTyr(CH2)5 (Me)AVP (50 microg/kg, intravenously) blocked the pressor response evoked by the NA microinjection into the vlPAG. Additionally, circulating vasopressin content was found to be significantly increased after NA microinjection in the vlPAG. The results suggest that activation of noradrenergic synapses within the vlPAG modulates vasopressin release in unanesthetized rats.

Dopamine D1 and D2 receptor agonism enhances antinociception mediated by the serotonin and noradrenaline reuptake inhibitor duloxetine in the rat formalin test

Altered functioning of monoamine-containing pathways descending from supraspinal structures to the spinal dorsal horn contributes to injury-induced sensitization of nociceptive transmission. Antidepressant drugs as typified by the dual serotonin (5-HT) and noradrenaline reuptake inhibitor duloxetine attenuate various signs and symptoms of persistent pain in animals and humans. The current study assessed whether dopamine receptor agonists could further enhance the antinociceptive activity of duloxetine in an animal model of injury-induced central sensitization, the rat formalin test. Duloxetine (3-100 mg/kg, s.c.), the dopamine D(1) receptor agonist SKF-82958 (0.1-1 mg/kg, s.c.) and the dopamine D(2) receptor agonist quinpirole (0.003-0.1 mg/kg, s.c.) all significantly attenuated spontaneous nociceptive behaviours during the second phase of the test; duloxetine and quinpirole also attenuated nociceptive behaviours during first phase and interphase. These antinociceptive actions of SKF-82958 and quinpirole were selectively antagonized by SCH 23390 and eticlopride respectively. Remarkably, when completely inactive doses of duloxetine (3 mg/kg) and SKF-82958 (0.3 mg/kg) were combined, a marked attenuation of second phase nociceptive behaviours occurred (P<0.05 vs vehicle), indicative of analgesic synergy. Similarly, when an active antinociceptive dose of quinpirole (0.03 mg/kg, P<0.05 vs vehicle) was combined with an inactive dose of duloxetine (3 mg/kg), a potentiation of duloxetine-mediated antinociception was observed (P<0.001 vs vehicle). Taken together, these results suggest that antidepressant drugs that can enhance the activity of 5-HT, noradrenaline and dopamine neurotransmission within nociceptive pathways should provide a broader spectrum of antinociception than dual mechanism of action reuptake inhibitors in animal models of injury-induced persistent nociception.

Human epididymal and prostatic tracts of vas deferens: Different contraction response to noradrenaline stimulation in isolated organ bath assay

In the present study epididymal and prostatic portions of human vas deferens were separately isolated and stimulated with exogenous noradrenaline to study their contractile properties. The results displayed that the epididymal tract produced a phasic-tonic response, while the prostatic strip produced only a phasic response suggesting a different functional role of each vas deferens segment. Moreover, it has been verified if alpha(1)-adrenoceptor antagonists doxazosin, alphuzosin and terazosin could differently block the noradrenaline response in each segment. Doxazosin, the most potent antagonist, displayed similar potency in epididymal and prostatic tract (pA(2)=8.51 and 8.42, respectively). Analogously, alphuzosin, although less potent than doxazosin, displayed in the same tracts a superimposed potency (pA(2)=7.25 and 7.30, respectively). In contrast with doxazosin and alphuzosin, terazosin displayed higher potency in blocking the contractile response in prostatic tract (pA(2)=7.67) than in epididymal segment (pA(2)=6.43). These results showed that alpha(1)-adrenoceptor antagonists doxazosin and alphuzosin, although with a different potency, did not discriminate between epididymal and prostatic segment while terazosin showed high potency in prostatic tract and only a moderate activity in epididymal section. Moreover, the biological model employed in our experiments could be a valid screening method to test the potential interferences of drugs indicated for bladder outlet obstruction with the peristaltic activity or the global tone of the human vas deferens.