Α2-adrenergic Agonist Clonidine Research Articles

A Comparative Study of the Antiemetic Effects of α2-Adrenergic Receptor Agonists Clonidine and Dexmedetomidine against Diverse Emetogens in the Least Shrew (Cryptotis parva) Model of Emesis.

In contrast to cats and dogs, here we report that the α2-adrenergic receptor antagonist yohimbine is emetic and corresponding agonists clonidine and dexmedetomidine behave as antiemetics in the least shrew model of vomiting. Yohimbine (0, 0.5, 0.75, 1, 1.5, 2, and 3 mg/kg, i.p.) caused vomiting in shrews in a bell-shaped and dose-dependent manner, with a maximum frequency (0.85 ± 0.22) at 1 mg/kg, which was accompanied by a key central contribution as indicated by increased expression of c-fos, serotonin and substance P release in the shrew brainstem emetic nuclei. Our comparative study in shrews demonstrates that clonidine (0, 0.1, 1, 5, and 10 mg/kg, i.p.) and dexmedetomidine (0, 0.01, 0.05, and 0.1 mg/kg, i.p.) not only suppress yohimbine (1 mg/kg, i.p.)-evoked vomiting in a dose-dependent manner, but also display broad-spectrum antiemetic effects against diverse well-known emetogens, including 2-Methyl-5-HT, GR73632, McN-A-343, quinpirole, FPL64176, SR141716A, thapsigargin, rolipram, and ZD7288. The antiemetic inhibitory ID50 values of dexmedetomidine against the evoked emetogens are much lower than those of clonidine. At its antiemetic doses, clonidine decreased shrews' locomotor activity parameters (distance moved and rearing), whereas dexmedetomidine did not do so. The results suggest that dexmedetomidine represents a better candidate for antiemetic potential with advantages over clonidine.

Norepinephrine modulation of heat dissipation in female rats lacking estrogen.

Postmenopausal hot flushes are caused by lack of estradiol (E2) but their neuroendocrine basis is still poorly understood. Here, we investigated the interrelationship between norepinephrine and hypothalamic neurons, with emphasis on kisspeptin neurons in the arcuate nucleus (ARC), as a regulatory pathway in the vasomotor effects of E2. Ovariectomized (OVX) rats displayed increased tail skin temperature (TST), and this increase was prevented in OVX rats treated with E2 (OVX + E2). Expression of Fos in the hypothalamus and the number of ARC kisspeptin neurons coexpressing Fos were increased in OVX rats. Likewise, brainstem norepinephrine neurons of OVX rats displayed higher Fos immunoreactivity associated with the increase in TST. In the ARC, the density of dopamine-ß-hydroxylase (DBH)-immunoreactive (ir) fibers was not altered by E2 but, importantly, DBH-ir terminals were found in close apposition to kisspeptin cells, revealing norepinephrine inputs to ARC kisspeptin neurons. Intracerebroventricular injection of the α2-adrenergic agonist clonidine (CLO) was used to reduce central norepinephrine release, confirmed by the decreased 3-methoxy-4-hydroxyphenylglycol/norepinephrine ratio in the preoptic area and ARC. Accordingly, CLO treatment in OVX rats reduced ARC Kiss1 mRNA levels and TST to the values of OVX + E2 rats. Conversely, CLO stimulated Kiss1 expression in the anteroventral periventricular nucleus (AVPV) and increased luteinizing hormone secretion. These findings provide evidence that augmented heat dissipation in OVX rats involves the increase in central norepinephrine that modulates hypothalamic areas related to thermoregulation, including ARC kisspeptin neurons. This neuronal network is suppressed by E2 and its imbalance may be implicated in the vasomotor symptoms of postmenopausal hot flushes.

Impact of Oral Clonidine on Duration of Opioid and Benzodiazepine Use in Mechanically Ventilated Children: A Randomized, Double-Blind, Placebo-Controlled Study.

Long term use of opioids and benzodiazepines are associated with important untoward effects. The α2 adrenergic agonist clonidine has sedative effects. Our goal was to study clonidine addition to total doses of fentanyl and midazolam and duration of ventilation in pediatric ICU (PICU). This randomized, double-blind, and placebo-controlled trial was conducted in PICU of Mofid Children Hospital. Hundred children aged from 2 to 15 years were randomized in 1:1 ratio to receive 5 μg/kg oral clonidine every 6 h or placebo plus 1-5 µg/kg/hr IV fentanyl and 0.05- 0.1 mg/kg/hr IV midazolam. Daily use of fentanyl and midazolam were measured. Ramsay sedation score was used for evaluation of sedation. A total of 96 patients were studied. The patients in placebo group received more midazolam and fentanyl compared with the patients in intervention group. Mean total dose of midazolam was 4.3 ± 2.2 mg in the placebo group and 2.7 ± 2.9 mg in the intervention group (P<0.05). Mean total dose of fentanyl was 34.4 ± 23.1 µg in the placebo group and 18.9 ± 10 µg in the intervention group (P<0.01). No significant differences were observed in duration of ventilation and length of PICU stay. No case of severe adverse effects was seen. This trial showed a reduction in total doses of midazolam and fentanyl given in ventilated children who were administered clonidine as add-on therapy. Clonidine addition had no effect on duration of mechanical ventilation.

Central Norepinephrine‐Kisspeptin Pathway as Part of the Vaso‐motor Effects of Estrogen in an Animal Model of Menopausal Hot Flashes

Menopausal transition includes the vasomotor disturbance hot flash as a significant symptom. Thus, the lack of estrogen has pronounced effects on thermoregulation, but how estrogen modulates thermoregulation remains poorly understood. Both norepinephrine (NE) and kisspeptin (Kp) have been shown to be involved in the central control of body temperature. In this work, we investigated the role of NE in the activation of hypothalamic Kp neurons and vasomotor effects caused by the lack of 17β‐estradiol (E2) in ovariectomized (OVX) rats. The first experiment was designed to determine the effects of E2 on tail skin temperature (TST) and correlate neuronal activation. Adult female rats were OVX and implanted with subcutaneous Silastic capsules containing oil (OVX) or E2 (6 ug/capsule/rat; OVX+E2). The TST was recorded for 2 hours on days 3, 7 and 14 after surgery. Rats were perfused on the morning of day 14 and the brains were processed for immunohistochemistry. OVX+E2 rats displayed greater uterine weight than OVX rats. The TST was higher in OVX compared to OVX+E2 rats at 7 and 14 days after ovariectomy. On day 14, OVX rats displayed an increased percentage of tyrosine hydroxylase (TH)‐immunoreactive (ir) neurons expressing Fos in the A1, A2 and locus coeruleus (LC), which was positively correlated with TST. The number of Fos‐ir neurons was also higher in the anteroventral periventricular (AVPV), median preoptic (MnPO), medial preoptic (MPO), and paraventricular (PVN) nuclei of OVX rats compared with OVX+E2. In the arcuate nucleus (ARC), the numbers of Kp single‐labeled and Fos/Kp double‐labeled neurons were markedly higher in OVX rats. In a second experiment, we investigated whether NE projections to the hypothalamus would drive the activity of Kp neurons in OVX rats. The α2‐adrenergic agonist clonidine (CLO) was used to reduce central norepinephrine release and TST and Kiss1 gene expression were measured. OVX and OVX+E2 rats received daily intracerebroventricular injections of CLO (10 ug/3 μL/rat; OVX+CLO) or vehicle (OVX+V and OVX+E2+V) on days 12, 13 and 14 after ovariectomy. OVX+V rats displayed higher TST than OVX+E2+V, and this response was completely restored in OVX+CLO rats, whose TST was similar to that of OVX+E2+V rats. The same response was found for Kiss1 mRNA in the ARC, with higher expression in OVX than in OVX+E 2, and levels fully restored in OVX+CLO rats. On the other hand, CLO significantly increased Kiss1 expression in the AVPV of OVX+CLO rats compared to OVX+V and OVX+E2+V rats, and this response was associated with an increased secretion of luteinizing hormone (LH) in OVX + CLO rats. Thus, the increase in TST caused by the absence of E2 in OVX rats is associated with an increased activity of noradrenergic and hypothalamic nuclei and seems to depend on the NE activation of Kp neurons in the ARC. These findings provide evidence of the involvement of a central NE‐Kp pathway as part of the vasomotor effects of estrogen, with possible implication in origin of postmenopausal hot flash.Support or Funding InformationCNPq; FAPEMIGThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect Of α2-Adrenergic Agonists And Antagonists On Cytokine Release From Human Lung Macrophages Cultured In Vitro.

The most trusted hypothesis to explain how α2-adrenergic agonists may preserve pulmonary functions in critically ill patients is that they directly act on macrophages by interfering with an autocrine/paracrine adrenergic system that controls cytokine release through locally synthetized noradrenaline and α1- and α2-adrenoreceptors. We tested this hypothesis in primary cultures of resident macrophages from human lung (HLMs). HLMs were isolated by centrifugation on percoll gradients from macroscopically healthy human lung tissue obtained from four different patients at the time of lung resection for cancer. HLMs from these patients showed a significant expression of α2A, α2B and α2C adrenoreceptors both at the mRNA and at the protein level. To evaluate whether α2 adrenoreceptors controlled cytokine release from HMLs, we measured IL-6, IL-8 and TNF-α concentrations in the culture medium in basal conditions and after preincubation with several α2-adrenergic agonists or antagonists. Neither the pretreatment with the α2-adrenergic agonists clonidine, medetomidine or dexdemetomidine or with the α2-adrenergic antagonist yohimbine caused significant changes in the response of any of these cytokines to LPS. These results show that, different from what reported in rodents, clonidine and dexdemetomidine do not directly suppress cytokine release from human pulmonary macrophages. This suggests that alternative mechanisms such as effects on immune cells activation or the modulation of autonomic neurotransmission could be responsible for the beneficial effects of these drugs on lung function in critical patients.

Osmotic versus adrenergic control of ion transport by ionocytes of Fundulus heteroclitus in the cold

In eurythermic vertebrates, acclimation to the cold may produce changes in physiological control systems. We hypothesize that relatively direct osmosensitive control will operate better than adrenergic receptor mediated control of ion transport in cold vs. warm conditions. Fish were acclimated to full strength seawater (SW) at 21°C and 5°C for four weeks, gill samples and blood were taken and opercular epithelia mounted in Ussing style chambers. Short-circuit current (Isc) at 21°C and 5°C (measured at acclimation temperature), was significantly inhibited by the α2-adrenergic agonist clonidine but the ED50 dose was significantly higher in cold conditions (93.8±16.4nM) than in warm epithelia (47.8±8.1nM) and the maximum inhibition was significantly lower in cold (−66.1±2.2%) vs. warm conditions (−85.6±1.3%), indicating lower sensitivity in the cold. β-Adrenergic responses were unchanged. Hypotonic inhibition of Isc, was higher in warm acclimated (−95%), compared to cold acclimated fish (−75%), while hypertonic stimulations were the same, indicating equal responsiveness to hyperosmotic stimuli. Plasma osmolality was significantly elevated in cold acclimated fish and, by TEM, gill ionocytes from cold acclimated fish had significantly shorter mitochondria. These data are consistent with a shift in these eurythermic animals from complex adrenergic control to relatively simple biomechanical osmotic control of ion secretion in the cold.

Treatment of Attention-Deficit/Hyperactivity Disorder in Adolescents

Although attention-deficit/hyperactivity disorder (ADHD) is highly prevalent in adolescents and often persists into adulthood, most studies about treatment were performed in children. Less is known about ADHD treatment in adolescents. To review the evidence for pharmacological and psychosocial treatment of ADHD in adolescents. The databases of CINAHL Plus, MEDLINE, PsycINFO, ERIC, and the Cochrane Database of Systematic Reviews were searched for articles published between January 1, 1999, and January 31, 2016, on ADHD treatment in adolescents. Additional studies were identified by hand-searching reference lists of retrieved articles. Study quality was rated using McMaster University Effective Public Health Practice Project criteria. The evidence level for treatment recommendations was based on Oxford Centre for Evidence-Based Medicine criteria. Sixteen randomized clinical trials and 1 meta-analysis, involving 2668 participants, of pharmacological and psychosocial treatments for ADHD in adolescents aged 12 years to 18 years were included. Evidence of efficacy was stronger for the extended-release methylphenidate and amphetamine class stimulant medications (level 1B based on Oxford Centre for Evidence-Based Medicine criteria) and atomoxetine than for the extended-release α2-adrenergic agonists guanfacine or clonidine (no studies). For the primary efficacy measure of total symptom score on the ADHD Rating Scale (score range, 0 [least symptomatic] to 54 [most symptomatic]), both stimulant and nonstimulant medications led to clinically significant reductions of 14.93 to 24.60 absolute points. The psychosocial treatments combining behavioral, cognitive behavioral, and skills training techniques demonstrated small- to medium-sized improvements (range for mean SD difference in Cohen d, 0.30-0.69) for parent-rated ADHD symptoms, co-occurring emotional or behavioral symptoms, and interpersonal functioning. Psychosocial treatments were associated with more robust (Cohen d range, 0.51-5.15) improvements in academic and organizational skills, such as homework completion and planner use. Evidence supports the use of extended-release methylphenidate and amphetamine formulations, atomoxetine, and extended-release guanfacine to improve symptoms of ADHD in adolescents. Psychosocial treatments incorporating behavior contingency management, motivational enhancement, and academic, organizational, and social skills training techniques were associated with inconsistent effects on ADHD symptoms and greater benefit for academic and organizational skills. Additional treatment studies in adolescents, including combined pharmacological and psychosocial treatments, are needed.

Practitioner Review: Treatments for Tourette syndrome in children and young people - a systematic review.

Tourette syndrome (TS) and chronic tic disorder (CTD) affect 1-2% of children and young people, but the most effective treatment is unclear. To establish the current evidence base, we conducted a systematic review of interventions for children and young people. Databases were searched from inception to 1 October 2014 for placebo-controlled trials of pharmacological, behavioural, physical or alternative interventions for tics in children and young people with TS or CTD. Certainty in the evidence was assessed with the GRADE approach. Forty trials were included [pharmacological (32), behavioural (5), physical (2), dietary (1)]. For tics/global score there was evidence favouring the intervention from four trials of α2-adrenergic receptor agonists [clonidine and guanfacine, standardised mean difference (SMD)=-0.71; 95% CI -1.03, -0.40; N=164] and two trials of habit reversal training (HRT)/comprehensive behavioural intervention (CBIT) (SMD=-0.64; 95% CI -0.99, -0.29; N=133). Certainty in the effect estimates was moderate. A post hoc analysis combining oral clonidine/guanfacine trials with a clonidine patch trial continued to demonstrate benefit (SMD=-0.54; 95% CI -0.92, -0.16), but statistical heterogeneity was high. Evidence from four trials suggested that antipsychotic drugs improved tic scores (SMD=-0.74; 95% CI -1.08, -0.40; N=76), but certainty in the effect estimate was low. The evidence for other interventions was categorised as low or very low quality, or showed no conclusive benefit. When medication is considered appropriate for the treatment of tics, the balance of clinical benefits to harm favours α2-adrenergic receptor agonists (clonidine and guanfacine) as first-line agents. Antipsychotics are likely to be useful but carry the risk of harm and so should be reserved for when α2-adrenergic receptor agonists are either ineffective or poorly tolerated. There is evidence that HRT/CBIT is effective, but there is no evidence for HRT/CBIT alone relative to combining medication and HRT/CBIT. There is currently no evidence to suggest that the physical and dietary interventions reviewed are sufficiently effective and safe to be considered as treatments.

Clonidine Restores Pressor Responsiveness to Phenylephrine and Angiotensin II in Ovine Sepsis.

In sepsis, prolonged, sympathetic overstimulation may lead to vasopressor-refractory hypotension. We therefore examined the effects of the α2-adrenergic agonist clonidine on mean arterial pressure, renal sympathetic nerve activity, and pressor responsiveness to phenylephrine and angiotensin II during hypotensive sepsis in conscious sheep. Interventional study. Research institute. Twelve adult Merino ewes (n = 6 per group). Sepsis was induced by IV infusion of Escherichia coli for 32 hours. Pressor responses to increasing doses of phenylephrine and angiotensin II were measured at baseline and at 24, 28, and 32 hours of sepsis. Sheep were treated with clonidine (1 μg/kg/hr) or saline-vehicle from 24 to 32 hours of sepsis. Sepsis was characterized by hypotension (~12 mm Hg), increased heart rate (~80 beats/min), increased renal sympathetic nerve activity (~70%), and blunted pressor responses to phenylephrine and angiotensin II. In vehicle-treated sheep, mean arterial pressure progressively declined from 25 to 32 hours of sepsis (73 ± 3 to 66 ± 3 mm Hg; p = 0.013) while the elevations in heart rate and renal sympathetic nerve activity and reduced pressor responsiveness to vasopressors persisted. Clonidine treatment prevented the further decline in mean arterial pressure, substantially reduced heart rate and renal sympathetic nerve activity and restored pressor responsiveness to both phenylephrine and angiotensin II toward preseptic levels. Administration of clonidine during hypotensive sepsis reduced renal sympathetic nerve activity, restored vascular sensitivity to both phenylephrine and angiotensin II, and resulted in better preservation of arterial pressure. Considering these findings, a clinical trial for the use of clonidine in the treatment of persistent vasopressor-refractory hypotension in patients with septic shock would be worthwhile.

Corneal Anesthesia With Site 1 Sodium Channel Blockers and Dexmedetomidine.

Amino-amide or amino-ester local anesthetics, which are currently used for topical ocular anesthesia, are short acting and may delay corneal healing with long-term use. In contrast, site 1 sodium channel blockers (S1SCBs) are potent local anesthetics with minimal adverse tissue reaction. In this study, we examined topical local anesthesia with two S1SCBs, tetrodotoxin (TTX) or saxitoxin (STX) individually or in combination with α2-adrenergic receptor agonists (dexmedetomidine or clonidine), and compared them with the amino-ester ocular anesthetic proparacaine. The effect of test solutions on corneal healing was also studied. Solutions of TTX ± dexmedetomidine, TTX ± clonidine, STX ± dexmedetomidine, dexmedetomidine, or proparacaine were applied to the rat cornea. Tactile sensitivity was measured by recording the blink response to probing of the cornea with a Cochet-Bonnet esthesiometer. The duration of corneal anesthesia was calculated. Cytotoxicity from anesthetic solutions was measured in vitro. The effect on corneal healing was measured in vivo after corneal debridement followed by repeated drug administration. Addition of dexmedetomidine to TTX or STX significantly prolonged corneal anesthesia beyond that of either drug alone, whereas clonidine did not. Tetrodotoxin or STX coadministered with dexmedetomidine resulted in two to three times longer corneal anesthesia than did proparacaine. S1SCB-dexmedetomidine formulations were not cytotoxic. Corneal healing was not delayed significantly by any of the test solutions. Coadministration of S1SCBs with dexmedetomidine provided prolonged corneal anesthesia without delaying corneal wound healing. Such formulations may be useful for the management of acute surgical and nonsurgical corneal pain.

Adrenergic Regulation of Somatolactin Gene Expression in Tilapia Pituitary Cells

Epinephrine is an important neuroendocrine regulator to control growth hormone (GH) secretion in vertebrates. Somatolactin (SL), the latest member of the GH family, is a novel pituitary hormone with diverse functions in fish. In a previous report it was shown that epinephrine had a potent inhibitory effect on SL release in fish. However, very little is known about the mechanisms responsible for epinephrine inhibition of SL gene expression. In primary cultures of tilapia neurointermediate lobe (NIL) cells, epinephrine not only reduced SL mRNA levels, but could also abolish pituitary adenylate cyclase-activating polypeptide (PACAP)-stimulated SL gene expression. The inhibitory effects of epinephrine on SL gene expression were mimicked by additions of α2-adrenergic agonists clonidine and UK14304, whereas similar treatments with the α1-agonist cirazoline or the β-agonist isoproterenol had no effects in this regard. In parallel experiments, the SL response to epinephrine was significantly abolished by co-incubations with the α2- antagonist yohimbine, but the α1- or β-antagonist was not effective in this regard. In tilapia NIL cells, the α2-adrenergic agonist clonidine suppressed cAMP production and blocked forskolin and PACAP induction of total cAMP production. By using a pharmacological approach, the adenylate cyclase (AC) activator- and cAMP analog-stimulated SL responses were blocked treatment with clonidine. Furthermore, adrenergic inhibition of SL gene expression was also mimicked by inhibiting AC and blocking protein kinase A (PKA). These results, as a whole, suggest that α2-adrenergic stimulation can downregulate SL gene transcription by inhibiting the AC/cAMP-dependent mechanism at the tilapia pituitary level.

Cold acclimation allows regulation of chloride secretion in a eurythermic teleost fish Fundulus heteroclitus

Fundulus heteroclitus (mummichog or common killifish) is an ideal model for ion transport regulation in chloride cells of the opercular epithelium (OE) and the response to thermal challenge. Mummichogs were acclimated to warm (20°C) and cold (5°C) seawater and opercular epithelia dissected and mounted in isolated Ussing-style epithelia chambers. The α2 adrenergic agonist clonidine inhibited the Cl− secretion (measured as short-circuit current, Isc), while the β-adrenergic agonist isoproterenol and 1.0mM dibutyryl cyclic adenosine monophosphate (db-cAMP) plus 0.1mM isobutyl methylxanthine (IBMX) stimulated Isc in OE from warm and cold acclimated fish, measured at 20°C. In contrast, rapid cooling partially inhibited Isc, but totally blocked the inhibition by clonidine and stimulation by isoproterenol and db-cAMP+IBMX in OE from warm-acclimated fish, while OE from cold-acclimated animals responded normally at 5°C. Warming epithelia from 5°C to 20°C restored Isc and stimulation by db-cAMP+IBMX markedly increased Isc to levels similar to warm acclimated epithelia, while isoproterenol was much less effective. The isoproterenol insensitivity suggests a downregulation of β-adrenergic receptors in the cold. We infer from present results and previous work (Buhariwalla et al. 2012) that cold shock of plasma membranes induces a phase shift from liquid to gel state that impaired plasma membrane protein mobility of necessary hormone regulatory functions, while cold acclimation preserved ion transport regulation via homeoviscous adaptation of plasma membrane lipids.

Effects of Clonidine in Women With Fecal Incontinence

Some women with urge-predominant fecal incontinence (FI) have diarrhea-predominant irritable bowel syndrome and a stiffer and hypersensitive rectum. We evaluated the effects of the α2-adrenergic agonist clonidine on symptoms and anorectal functions in women with FI in a prospective, placebo-controlled trial. We assessed bowel symptoms and anorectal functions (anal pressures, rectal compliance, and sensation) in 43 women (age, 58 ± 2 y) with urge-predominant FI, randomly assigned to groups given oral clonidine (0.1 mg, twice daily) or placebo for 4 weeks. Before and after administration of the medication, anal pressures were evaluated by manometry, and rectal compliance and sensation were measured using a barostat. Anal sphincter injury was evaluated by endoanal magnetic resonance imaging. Bowel symptoms were recorded in daily and weekly diaries. The primary end point was the FI and Constipation Assessment symptom severity score. FI scores decreased from 9.1 ± 0.3 to 7.6 ± 0.5 among subjects given placebo and from 8.1 ± 0.4 to 6.5 ± 0.6 among patients given clonidine. Clonidine did not affect FI symptom severity, bowel symptoms (stool consistency or frequency), anal pressures, rectal compliance, or sensation compared with placebo. However, when baseline data were used to categorize subjects as those with or without diarrhea, clonidine reduced the proportion of loose stools in patients with diarrhea only (P = .018). Clonidine also reduced the proportion of days with FI in patients with diarrhea (P = .0825). Overall, clonidine did not affect bowel symptoms, fecal continence, or anorectal functions, compared with placebo, in women with urge-predominant FI. Among patients with diarrhea, clonidine increased stool consistency, with a borderline significant improvement in fecal continence. ClinicalTrials.gov, Number NCT00884832.

Efficacy of Multimodal Perioperative Analgesia Protocol With Periarticular Medication Injection in Total Knee Arthroplasty

Pain control is necessary for successful rehabilitation and outcome after total knee arthroplasty. Our goal was to compare the clinical efficacy of periarticular injections consisting of a long-acting local anesthetic (ropivacaine) and epinephrine with and without combinations of an α2-adrenergic agonist (clonidine) and/or a nonsteroidal anti-inflammatory agent (ketorolac). In a double-blinded controlled study, we randomized 160 patients undergoing total knee arthroplasty to receive 1 of 4 intraoperative periarticular injections: Group A, ropivacaine, epinephrine, ketorolac, and clonidine; Group B, ropivacaine, epinephrine, and ketorolac; Group C, ropivacaine, epinephrine, and clonidine; Group D (control), ropivacaine and epinephrine. Compared with Group D, Group A and B patients had significantly lower postoperative visual analog pain scores and nurse pain assessment and Group C patients had a significantly greater reduction in physical therapist pain assessment. We found no differences in other parameters analyzed.

Feeding behaviour after injection of α-adrenergic receptor agonists into the median raphe nucleus of food-deprived rats

This study investigated the participation of median raphe nucleus (MnR) α1-adrenergic receptors in the control of feeding behaviour. The α1-adrenergic agonist phenylephrine (PHE) and α2-adrenergic agonist clonidine (CLON) (at equimolar doses of 0, 6 and 20nmol) were injected into the MnR of: a) rats submitted to overnight fasting (18h); or b) rats maintained with 15g of lab chow/day for 7days. Immediately after the drug injections, the animals were placed in the feeding chamber and feeding and non-ingestive behaviours such as grooming, rearing, resting, sniffing and locomotion were recorded for 30min. The results showed that both doses of PHE injected into the MnR of overnight fasted animals decreased food intake accompanied by an increase in the latency to start feeding. A reduction in feeding duration was observed only after treatment of the MnR with the 20nmol dose of PHE. Both locomotion duration and sniffing frequency increased after injection with the highest dose PHE into the MnR. Feeding frequency and the other non-ingestive behaviours remained unchanged after PHE treatment in the MnR. Both doses of PHE injected into the MnR of food-restricted rats decreased food intake. This hypophagic response was accompanied by a decrease in feeding duration only after treatment of the MnR with the highest dose of PHE. The latency to start feeding and feeding frequency were not affected by injection of either dose of PHE into the MnR. While both doses of PHE increased sniffing duration, the highest dose of PHE increased resting duration and resting frequency. Treatment with CLON into the MnR did not affect feeding behaviour in either of the food deprivation conditions. The present results indicate the inhibitory functional role of α1-adrenergic receptors within the MnR on feeding behaviour.

Effects of clonidine and idazoxan on tetrathiomolybdate-induced copper and lysosomal enzyme excretion into sheep bile

This study investigated the effects of intravenous (IV) administration of tetrathiomolybdate (TTM), and α2-adrenergic agonist clonidine (CLO) and α2-antagonist idazoxan (IDA), alone or in combination with TTM, on sheep fed low (LCu) and high (HCu) copper diets. Effects on bile flow, biliary Cu concentration and excretion, plasma Cu concentration, and lysosomal enzyme β-glucuronidase (β-GLU) activity in bile and plasma were determined. Tetrathiomolybdate alone or with CLO or IDA significantly enhanced biliary Cu excretion most likely by removing Cu from hepatocyte lysosomes as evidenced by a significant increase in β-GLU enzyme activity in bile. A significant increase in plasma β-GLU concentration occurred only in sheep treated with CLO in combination with TTM. Because of the lytic nature of the lysosomal enzymes, caution is advocated in use of drugs, especially α2-adrenergic agonists, to further enhance TTM-induced biliary Cu excretion in the treatment of chronic Cu poisoning in sheep.

Subthreshold α2-Adrenergic Activation Counteracts Glucagon-Like Peptide-1 Potentiation of Glucose-Stimulated Insulin Secretion

The pancreatic β cell harbors α 2-adrenergic and glucagon-like peptide-1 (GLP-1) receptors on its plasma membrane to sense the corresponding ligands adrenaline/noradrenaline and GLP-1 to govern glucose-stimulated insulin secretion. However, it is not known whether these two signaling systems interact to gain the adequate and timely control of insulin release in response to glucose. The present work shows that the α 2-adrenergic agonist clonidine concentration-dependently depresses glucose-stimulated insulin secretion from INS-1 cells. On the contrary, GLP-1 concentration-dependently potentiates insulin secretory response to glucose. Importantly, the present work reveals that subthreshold α 2-adrenergic activation with clonidine counteracts GLP-1 potentiation of glucose-induced insulin secretion. This counteractory process relies on pertussis toxin- (PTX-) sensitive Gi proteins since it no longer occurs following PTX-mediated inactivation of Gi proteins. The counteraction of GLP-1 potentiation of glucose-stimulated insulin secretion by subthreshold α 2-adrenergic activation is likely to serve as a molecular mechanism for the delicate regulation of insulin release.

Stimulation of α2-adrenergic receptors in the central nucleus of the amygdala attenuates stress-induced reinstatement of nicotine seeking in rats

Tobacco addiction is a chronic disorder that is characterized by craving for tobacco products, withdrawal upon smoking cessation, and relapse after periods of abstinence. Previous studies demonstrated that systemic administration of α2-adrenergic receptor agonists attenuates stress-induced reinstatement of drug seeking in rats. The aim of the present experiments was to investigate the role of noradrenergic transmission in the central nucleus of amygdala (CeA) in stress-induced reinstatement of nicotine seeking. Rats self-administered nicotine for 14–16 days and then nicotine seeking was extinguished by substituting saline for nicotine. The effect of the intra-CeA infusion of the α2-adrenergic receptor agonists clonidine and dexmedetomidine, the nonselective β1/β2-adrenergic receptor antagonist propranolol, and the α1-adrenergic receptor antagonist prazosin on stress-induced reinstatement of nicotine seeking was investigated. In all the experiments, exposure to footshocks reinstated extinguished nicotine seeking. The administration of clonidine or dexmedetomidine into the CeA attenuated stress-induced reinstatement of nicotine seeking. The administration of propranolol or prazosin into the CeA did not affect stress-induced reinstatement of nicotine seeking. Furthermore, intra-CeA administration of clonidine or dexmedetomidine did not affect operant responding for food pellets. This suggests that the effects of clonidine and dexmedetomidine on stress-induced reinstatement of nicotine seeking were not mediated by motor impairments or sedation. Taken together, these findings indicate that stimulation of α2-adrenergic receptors, but not blockade of α1 or β-adrenergic receptors, in the CeA attenuates stress-induced reinstatement of nicotine seeking. These findings suggest that α2-adrenergic receptor agonists may at least partly attenuate stress-induced reinstatement of nicotine seeking by stimulating α2-adrenergic receptors in the CeA.

New Drugs for Epidural Analgesia

In recent years there has been a wide use of the epidural technique not only during surgery to provide anesthesia and analgesia, but also for obstetric and trauma as well as acute, chronic and cancer pain states. Nowadays there is an increase in the number of the epidural drugs. Local anesthetics and opioids are still the pharmacological agents more widely used epidurally, nevertheless other drugs from different pharmacological classes are administered as adjuvant to local anesthetics and opioids or are in various early stages of investigation. Regarding to local anesthetics, the most recent literature focuses on the new enantiomers, ropivacaine and levobupivacaine, the efficacy of which is similar to that of bupivacaine with a reduced risk of cardiotoxicity. About opioids, the other class of drugs mainly used, the debate, in the last years, concerned the physicochemical properties of morphine and of the more recent lipophilic agents, fentanyl and sufentanil, in order to explain the main differences in efficacy and safety. Other categories of agents have been investigated for epidural administration, such as alpha(2)-adrenergic agonists clonidine and dexmedetomidine. They are being used increasingly as adjuvants to local anesthetics and opioids. Ketamine and neostigmine, the more recent studied drugs for epidural use, are still under investigation and are not part of routine clinical practice.

Endothelin-1 Inhibits Thick Ascending Limb Transport via Akt-stimulated Nitric Oxide Production

Endothelin-1 inhibits sodium reabsorption in the thick ascending limb (THAL) via stimulation of nitric oxide (NO) production. The mechanism whereby endothelin-1 stimulates THAL NO is unknown. We hypothesized that endothelin-1 stimulates THAL NO production by activating phosphatidylinositol 3-kinase (PI3K), stimulating Akt activity, and phosphorylating NOS3 at Ser1177. This enhances NO production and inhibits sodium transport. We measured 1) NO production by fluorescence microscopy using DAF2-DA, 2) Akt activity using a fluorescence resonance energy transfer-based Akt reporter, 3) phosphorylated NOS3 and Akt by Western blotting, and 4) NKCC2 activity by fluorescence microscopy. In isolated THAL, endothelin-1 (1 nmol/liter) increased NO production from 0.23 +/- 0.24 to 2.81 +/- 0.32 fluorescence units/min (p < 0.001; n = 5) but failed to stimulate NO production in THALs isolated from NOS3-/- mice. Wortmannin (150 nmol/liter), a PI3K inhibitor, reduced endothelin-1-stimulated NO by 83% (0.49 +/- 0.13 versus 3.31 +/- 0.49 fluorescence units/min for endothelin-1 alone; p < 0.006; n = 5). Endothelin-1 stimulated Akt activity by 0.16 +/- 0.02 arbitrary units as measured by fluorescence resonance energy transfer (p < 0.001; n = 5) and increased phosphorylation of Akt at Ser473 by 56 +/- 11% (p < 0.002; n = 7). Dominant-negative Akt blocked endothelin-1-induced NO by 60 +/- 8% (p < 0.001 versus control; n = 6), and an Akt inhibitor had a similar effect. Endothelin-1 increased phosphorylation of NOS3 at Ser1177 by 89 +/- 24% (p < 0.01; n = 7) but had no effect on Ser633. Endothelin-1 inhibited NKCC2 activity, an effect that was blocked by dominant-negative Akt and NOS inhibition. We conclude that endothelin-1 stimulates THAL NO production by activating PI3K, stimulating Akt activity, and phosphorylating NOS3 at Ser1177. This enhances NO production and inhibits sodium transport.