Alpha-2a adrenergic receptor activation in genetic absence epilepsy: An absence status model?

OBJECTIVE: The objective of the study was to propose a candidate animal model of absence status epilepticus induced by specific alpha-2a adrenergic receptor (α2AR) activation. We also aim to investigate the responsiveness of this model to classical anti-status or anti-absence medications. METHODS: An α2AR agonist, dexmedetomidine (DEX), was injected intracerebroventricularly into adult rats with genetic absence epilepsy, and their electroencephalography (EEG) was recorded. The total duration, number, and mean duration of each spike-and-wave discharges (SWDs) were evaluated. The blocks of absence status events were classified as the initial and second sets of absence statuses. Ethosuximide (ETX) was administered as a pretreatment to another group of rats and later injected with 2.5 µg DEX. In addition, ETX, valproic acid (VPA), diazepam (DIAZ), and atipamezole (ATI) were administered after induced status-like events following DEX administration. Power spectral characteristics and coherence analysis were performed on the EEG to assess the absence status events and sleep. RESULTS: The 2.5 µg dose of DEX increased the total SWD duration and induced continuous SWDs up to 26 min. Following the initial absence status event, sleep was induced; then, the second period of absence status-like activities were initiated. ETX pretreatment blocked the occurrence of absence status-like activities. Power spectral density analyses revealed that DEX-induced post-sleep activities had higher power in delta frequency band (1-4 Hz) and attenuated power of 7 Hz harmonics (14 and 21 Hz) than the pre-injection seizure. The mean duration of SWDs were decreased in all the groups, but occasional prolonged activities were seen in ETX or VPA-injected rats but not with DIAZ or ATI. SIGNIFICANCE: This study presents an absence status epilepticus animal model that is activated by α2AR activation to investigate the pathophysiological role of absence status. Unlike other agents ATI switched off the second set of absence statuses to normal SWDs, without sedation or lethargy, can show it may preferentially block absence status-like activity. THE PLAIN LANGUAGE SUMMARY: This study proposes a rat model for prolonged seizures, resembling absence status epilepticus. Activating the brain's alpha-2a adrenergic receptor with dexmedetomidine induced seizures lasting up to 26 minutes. Ethosuximide pretreatment and post-treatment with valproic acid, diazepam, and atipamezole decreased induced seizures. The findings suggest this model is valuable for studying absence status epilepticus. In addition, atipamezole normalized abnormal seizures without sedation, hinting at its potential for targeted treatment and further research.

Antinociceptive Action of Moringa peregrina is Mediated by an Interaction with α2-Adrenergic Receptor

Background: Moringa peregrina (M. peregrina) is an edible, drought-resistant tree that is native to semi-arid countries. It is used as a painkiller in folk medicine. Aims: To study the antinociceptive effects of the leaf extract of M. peregrina in mice. Study Design: Animal experimentation. Methods: We employed thermal (hot plate and tail-immersion tests) and chemical (writhing and formalin tests) pain models in male BALB/c mice (eight animals per group) to investigate the mechanisms involved in the antinociceptive actions of M. peregrina. Additionally, we identified the chemical constituents present in the extract of M. peregrina by using liquid chromatography-mass spectrometry analysis, and predicted the possible active constituents that interact with the receptor based on molecular docking simulations. Results: In the writhing test, 200 mg/kg of M. peregrina extract restricted abdominal cramps by up to 55.97% (p<0.001). Further, it reduced the time of paw-licking in the early and late phases of formalin test by up to 56.8% and 65.5%, respectively, as compared to the percentage inhibitions of 50.5% and 48.4% produced by 30 mg/kg diclofenac sodium in the early and late phases, respectively (p<0.05). This effect was abrogated by yohimbine (1 mg/kg, intraperitoneally), but not by methysergide (5 mg/kg, intraperitoneally), in the late phase only, which indicates that the action of M. peregrina in formalin test is not mediated by 5-HT2 serotonin receptors, but rather via α2-adrenergic receptors. In the hot plate test, but not on tail-immersion test, the high dose (400 mg/kg) of the extract increased the latency time after 30 minutes of its administration. Yohimbine antagonized the action of M. peregrina in the hot plate test. Based on LC-MS analysis, the major constituents found in M. peregrina methanolic extract were chrysoeriol 7-O-diglucoside, lupeol acetate, quercetin, and rutin. Depending on the molecular docking results, the activity of M. peregrina extract could be due to the binding of chrysoeriol 7-O-diglucoside, quercetin, and rutin to the α2-adrenergic receptor. Conclusion: Interaction with the α2-adrenergic receptor serves as a possible mechanism of the M. peregrina analgesic effect.

Pharmacological prevention of sevoflurane- and desflurane-related emergence agitation in children: a meta-analysis of published studies.

BACKGROUND: Emergence agitation (EA) in children is increased after sevoflurane anaesthesia. The efficacy of prophylactic treatment is controversial. The aim of this study was to provide a meta-analysis of the studies of the pharmacological prevention of EA in children. METHODS: A comprehensive literature search was conducted to identify clinical trials that focused on the prevention of EA in children anaesthetized with sevoflurane, desflurane, or both. The data from each trial were combined using the Mantel-Haenszel model to calculate the pooled odds ratio (OR) and 95% confidence interval. I(2) statistics were used to assess statistics heterogeneity and the funnel plot and the Begg-Mazumdar test to assess bias. RESULTS: Thirty-seven articles were found which included a total of 1695 patients in the intervention groups and 1477 in the control ones. Midazolam and 5HT(3) inhibitors were not found to have a protective effect against EA [OR=0.88 (0.44, 1.76); OR=0.39 (0.12, 1.31), respectively], whereas propofol [OR=0.21 (0.16, 0.28)], ketamine [OR=0.28 (0.13, 0.60)], alpha(2)-adrenoceptors [OR=0.23 (0.17, 0.33)], fentanyl [OR=0.31 (0.18, 0.56)], and peroperative analgesia [OR=0.15 (0.07, 0.34)] were all found to have a preventive effect. Subgroup analysis according to the peroperative analgesia given does not affect the results. CONCLUSIONS: This meta-analysis found that propofol, ketamine, fentanyl, and preoperative analgesia had a prophylactic effect in preventing EA. The analgesic properties of these drugs do not seem to have a role in this effect.

Neuroimmune perspectives in sepsis.

Physiologic anti-inflammatory mechanisms are selected by evolution to control the immune system and to prevent infectious and inflammatory disorders. Central-acting alpha2-agonists attenuate systemic inflammation and improve survival in experimental sepsis. This anti-inflammatory and therapeutic mechanism of central sympatholytics appears to be mediated by an unexpected vagomimetic potential of the alpha2-agonists to activate the vagus nerve. Recent studies, however, rule out a cholinergic anti-inflammatory mechanism based on a direct cholinergic interaction between the vagus nerve and the immune system. Since the nervous system is the principal regulator of the immune system, physiologic studies understanding the neuroimmune connections can provide major advantages to design novel therapeutic strategies for sepsis.

Alpha2 adrenergic agonists for the management of opioid withdrawal.

BACKGROUND: Withdrawal (detoxification) is necessary prior to drug-free treatment. It may also represent the end point of long-term treatment such as methadone maintenance. The availability of managed withdrawal is essential to an effective treatment system. OBJECTIVES: To assess the effectiveness of interventions involving the use of alpha2 adrenergic agonists (clonidine, lofexidine, guanfacine) to manage the acute phase of opioid withdrawal. SEARCH STRATEGY: Multiple electronic databases (including MEDLINE, EMBASE, PsycINFO, Australian Medical Index, Cochrane Clinical Trials Register) were systematically searched. Reference lists of retrieved studies, reviews and conference abstracts were handsearched and relevant pharmaceutical companies contacted. SELECTION CRITERIA: Controlled trials comparing alpha2 adrenergic agonists with reducing doses of methadone, symptomatic medications or placebo, or comparing different alpha2 adrenergic agonists to modify the signs and symptoms of withdrawal in participants who were primarily opioid dependent. DATA COLLECTION AND ANALYSIS: One reviewer assessed studies for inclusion and undertook data extraction. Inclusion decisions and the overall process were confirmed by consultation between all four reviewers. MAIN RESULTS: Twenty-two studies, involving 1691 participants, were included. Eighteen were randomised controlled trials; for the remaining studies allocation was by participant choice in one, another used alternate allocation and in two the method of allocation was unclear. Eleven studies compared a treatment regime based on an alpha2 adrenergic agonist with one based on reducing doses of methadone. Diversity in study design, assessment and reporting of outcomes limited the extent of quantitative analysis. For the comparison of alpha2 adrenergic agonist regimes with reducing doses of methadone, there were insufficient data for statistical analysis, but withdrawal intensity appears similar to, or marginally greater with alpha2 adrenergic agonists, while signs and symptoms of withdrawal occur and resolve earlier in treatment. Participants stay in treatment longer with methadone. No significant difference was detected in rates of completion of withdrawal with adrenergic agonists compared to reducing doses of methadone, or clonidine compared to lofexidine. Clonidine is associated with more adverse effects (low blood pressure, dizziness, dry mouth, lack of energy) than reducing doses of methadone. Lofexidine does not reduce blood pressure to the same extent as clonidine, but is otherwise similar to clonidine. REVIEWER'S CONCLUSIONS: No significant difference in efficacy was detected for treatment regimes based on the alpha2 adrenergic agonists clonidine and lofexidine, and those based on reducing doses of methadone over a period of around 10 days, for the management of withdrawal from heroin or methadone. Participants stay in treatment longer with methadone regimes and experience less adverse effects. The lower incidence of hypotension makes lofexidine more suited to use in outpatient settings than clonidine. There are insufficient data available to support a conclusion on the efficacy of other alpha2 adrenergic agonists.

Changing paradigms in the medical treatment of glaucoma.

Glaucoma is defined by a typical optic neuropathy accompanied by characteristic visual field loss and eventual blindness. The major risk factor for glaucoma is elevated intraocular pressure (IOP). Lowering IOP is currently the only proven method for reducing the risk of glaucomatous visual field loss and remains the primary goal of therapy. With the recent introduction of many new medications that lower IOP, the definition of what constitutes maximum tolerated medical therapy has been changing. The treatment can now be tailored better to each individual patient. The regimen needs to be affordable, easy to understand, and least interfering with the patient's quality of life. beta-blockers still are the mainstay of initial therapy, but more and more prostaglandin analogs and also alpha-2 agonists are being used initially. Systemic carbonic anhydrase inhibitors and cholinergics are being used less frequently.

Alpha2 adrenergic agonists for the management of opioid withdrawal.

BACKGROUND: Withdrawal (detoxification) is necessary prior to drug-free treatment. It may also represent the end point of long-term treatment such as methadone maintenance. The availability of managed withdrawal is essential to an effective treatment system. OBJECTIVES: To assess the effectiveness of interventions involving the use of alpha2 adrenergic agonists (clonidine, lofexidine, guanfacine, guanabenz acetate) to manage the acute phase of opioid withdrawal. SEARCH STRATEGY: Multiple electronic databases were systematically searched. Reference lists of retrieved studies, reviews and conference abstracts were handsearched and relevant pharmaceutical companies contacted. SELECTION CRITERIA: Randomised or quasi-randomised controlled trials that compared alpha2 adrenergic agonists with another form of treatment (or placebo) to modify the signs and symptoms of withdrawal in participants who were primarily opioid dependent. DATA COLLECTION AND ANALYSIS: One reviewer assessed studies for inclusion and undertook data extraction. Inclusion decisions and the overall process were confirmed by consultation between all four reviewers. MAIN RESULTS: Twenty-four studies, involving 1956 participants, were included. Nineteen were randomised controlled trials; in two allocation was by participant choice, one used alternate allocation and in two the method of allocation was unclear. Ten studies compared a treatment regime based on an alpha2 adrenergic agonist with one based on reducing doses of methadone. Diversity in study design, assessment and reporting of outcomes limited the extent of quantitative analysis. From the comparison of alpha2 adrenergic agonist regimes with reducing doses of methadone, withdrawal intensity is similar to, or marginally greater with alpha2 adrenergic agonists, but signs and symptoms of withdrawal occur and resolve earlier in treatment. Participants stay in treatment longer with methadone. The likelihood of completing withdrawal is similar, or slightly less, with clonidine or lofexidine. Clonidine is associated with more adverse effects (low blood pressure, dizziness, dry mouth, lack of energy) than reducing doses of methadone. Lofexidine does not reduce blood pressure to the same extent as clonidine, but is otherwise similar to clonidine. REVIEWER'S CONCLUSIONS: Treatment regimes based on the alpha2 adrenergic agonists clonidine and lofexidine, and those based on reducing doses of methadone over a period of around 10 days, have similar efficacy in the management of withdrawal from heroin or methadone. Participants stay in treatment longer with methadone regimes and experience less adverse effects. The lower incidence of hypotension makes lofexidine more suited to use in outpatient settings than lofexidine. There are insufficient data available to support a conclusion on the efficacy of guanfacine.

[Glaucoma as primary optic neuropathy]. / Glaucomul ca neuropatie optica primitiva.

The appearance of the new concept of glaucomatous optic neuropathy directed to idea that high intraocular pressure and vascular insufficiency in the optic nerve head are only risk factors in the appearance of glaucoma. Glaucomatous optic neuropathy is the consequence of progressive loss of the retinal ganglion cells whose axons comprise the optic nerve. A great number of neurotrophic agents are under investigation with the view of preventing the dead of retinal ganglion cells. Induction of cell rescue mechanisms may be an alternate and efficient strategy for neuroprotection. The paper presents both actual data about the pathophysiological mechanisms of glaucoma (neurotrophin deprivation, excitotoxicity caused by glutamate, "ischemic cascade", apoptosis of retinal ganglion cells) and neuroprotective and neuroregenerative therapy and antiapoptotic agents.