Effect of low concentrations of K+ and Cl− on the Na+-dependent neuronal uptake of [3H] dopamine

The specific uptake of [³H] dopamine (DA) was studied using a crude synaptosomal fraction obtained from rat striatum. In a medium containing a 10 mM NaHC03/NaH2PO4 buffer and no added K⁺ ions, addition of NaCl elicited an increase in DA uptake for Na⁺ concentrations from 10 to 60 mM, and then a decrease of uptake for Na⁺ concentrations up to 130 mM. These data confirm that rather low NaCl concentrations produce a maximal DA uptake. This biphasic curve of uptake resulted from significant changes in the V _max of the DA uptake. Except for 10 mM Na⁺, this curve was not significantly modified when 9 mM NaHCO₃/NaH₂PO₄ were replaced by 9 mM NaCl. This result indicates that the Cl^– dependence of the DA uptake is mainly secondary to the Na⁺ dependence. Addition of KCl up to 3 mM did not modify the ascending part of the NaCl-dependent uptake curve. In contrast, the reduction in uptake produced by high Na⁺ concentrations was prevented in a concentration-dependent manner by KCl; this effect resulted from a decrease in the K_m and an increase in the V _max for the uptake.Measurements of membrane potential, with the help of the fluorescent probe 3,3-diethylthiadicarbocyanine iodide [DiSC₂(5)] and purified synaptosomes prepared from rat striatum and cerebral cortex, revealed that addition of 3 mM KCl to a medium containing a high Na⁺ concentration and no K⁺ ions produced a marked and stable decrease in the fluorescence level. This decrease which corresponds to an increase in membrane polarization was blocked by 0.1 mM ouabain. These data suggest that low K⁺ concentrations are likely to prevent the decrease in uptake elicited by high Na⁺ concentrations by restoration, via a Na⁺/K⁺ ATPase-mediated mechanism, of the membrane potential and/or a transmembrane electrochemical Na⁺ gradient more favourable to DA uptake.     

Effect of K+ channel blockers on the α2-adrenoceptor-coupled regulation of electrically evoked noradrenaline release in hippocampus

Summary The question whether presynaptic ₂-adrenoceptors regulating noradrenaline release in hippocampus directly couple to tetraethylammonium chloride (TEA) or -dendrotoxin (-DTX)-sensitive K⁺ channels was investigated. Hippocampal slices, prelabelled with [³H] noradrenaline, were superfused in the presence of (+)-oxaprotiline and electrically stimulated with 4 pulses delivered at 100 Hz, in order to avoid autoinhibition due to released noradrenaline.TEA enhanced the evoked [³H]noradrenaline release in rabbit hippocampus in a concentration-dependent manner, yielding an approximately 4-fold increase at 30 mmol/l, whereas the spontaneous outflow of tritium was only slightly affected at this concentration. The ₂-adrenoceptor agonist clonidine, at 10–100 nmol/l inhibited the evoked [³H]noradrenaline release between 77% and 96%. The inhibitory effect of the ₂-agonist was distinctly diminished in the presence of 30 mmol/l TEA but was restored in low Ca²⁺/high Mg²⁺ buffer. Therefore, the diminution of the ₂-agonist effect by TEA observed in experiments with normal Ca²⁺ can be explained by an increase of the Ca²⁺ availability for the release process due to the prolongation of action potentials. In rabbit hippocampus -DTX (10–200 nmol/l) did neither affect the evoked release of [³H]noradrenaline nor its ₂-agonist-induced modulation. However, in rat hippocampus -DTX significantly increased the evoked transmitter release and diminished the effect of clonidine.Taken together, the present data for the rabbit hippocampus exclude the possibility that activation of presynaptic ₂-adrenoceptors inhibits depolarization-evoked [³H]noradrenaline release by inducing an outward K⁺ current through TEA- or -DTX-sensitive K⁺ channels. However, there are species differences between the rabbit and the rat so that in the rat the ₂-adrenoceptors could actually be coupled to K⁺ channels — provided that the release-enhancing properties of -DTX do not account for the ₂-antagonism observed.Correspondence to C. Allgaier at the above address     

Actions of KMUP‐1, a xanthine and piperazine derivative,on voltage‐gated Na+ and Ca2+‐activated K+ currents in GH3 pituitary tumour cells

Background and Purpose

7‐[2‐[4‐(2‐Chlorophenyl)piperazinyl]ethyl]‐1,3‐dimethylxanthine (KMUP‐1) is a xanthine‐based derivative. It has soluble GC activation and K⁺‐channel opening activity. Effects of this compound on ion currents in pituitary GH₃ cells were investigated in this study.

Experimental Approach

The aim of this study was to evaluate effects of KMUP‐1 on the amplitude and gating of voltage‐gated Na⁺ current (I _Na) in pituitary GH₃ cells and in HEKT293T cells expressing SCN5A. Both the amplitude of Ca²⁺‐activated K⁺ current and the activity of large‐conductance Ca²⁺‐activated K⁺ (BK_Ca) channels were also studied.

Key Results

KMUP‐1 depressed the transient and late components of I _Na with different potencies. The IC₅₀ values required for its inhibitory effect on transient and late I _Na were 22.5 and 1.8 μM respectively. KMUP‐1 (3 μM) shifted the steady‐state inactivation of I _Na to a hyperpolarized potential by −10 mV, despite inability to alter the recovery of I _Na from inactivation. In cell‐attached configuration, KMUP‐1 applied to bath increased BK_Ca‐channel activity; however, in inside‐out patches, this compound applied to the intracellular surface had no effect on it. It prolonged the latency in the generation of action currents elicited by triangular voltage ramps. Additionally, KMUP‐1 decreased the peak I _Na with a concomitant increase of current inactivation in HEKT293T cells expressing SCN5A.

Conclusions and Implications

Apart from activating BK_Ca channels, KMUP‐1 preferentially suppresses late I _Na. The effects of KUMP‐1 on ion currents presented here constitute an underlying ionic mechanism of its actions.

Abbreviations

AC

action current

AP

action potential

BK_Ca

channel large‐conductance Ca²⁺‐activated K⁺ channel

I_K(Ca)

Ca²⁺‐activated K⁺ current

I_Na

voltage‐gated Na⁺ current

I–V

current versus voltage

K_ATP

channel ATP‐sensitive K⁺ channel

ODQ

1H‐[1,2,4]oxadiazolo‐[4,3‐a] quinoxalin‐1‐one

TEA

tetraethylammonium chloride

τ_inact(S)

slow component of inactivation time constant for I _Na

YC‐1

3‐(5′‐hydroxymethyl‐2′‐furyl)‐1‐benzylindazole

     

Inhibitory action of methadone and its metabolites on erg-mediated K+ current in GH₃ pituitary tumor cells

Methadone (Mtd) is a widely used opioid drug associated with the side effect of hyperprolactinemia. The mechanism of how Mtd induces prolactin secretion remains unclear. The effects of Mtd and its two main metabolites (EDDP: (±)-2-ethyl-1,5-dimethyl-3,3-diphenylpyrrolinium percholarate and EMDP: 2-ethyl-5-methyl-3,3-dipnehyl-1-pyrroline) on ion currents were investigated in GH? pituitary tumor cells. Hyperpolarization-elicited K+ currents in GH? cells bathed in a high-K(+), Ca(2+)-free solution were studied to evaluate the effects of Mtd and other related compounds on the ether-à-go-go-related-gene (erg) K(+) current (I(K(erg))). Mtd suppressed the amplitude of I(K(erg)) in a concentration-dependent manner with an IC(50) value of 10.4 μM. With the aid of a minimal binding scheme, the inhibitory action of Mtd on I(K(erg)) was estimated with a dissociation constant of 8.2 μM. Mtd tended to increase the rate of I(K(erg)) deactivation in a voltage-dependent fashion. EDDP (10 μM) had no effect on I(K(erg)), while EMDP (10μM) slightly suppressed it. In GH? cells incubated with naloxone (30 μM), the Mtd-induced inhibition of I(K(erg)) remained unaltered. Under cell-attached voltage-clamp recordings, Mtd increased the frequency of spontaneous action currents with no change in current amplitude. Similarly, Mtd can suppress I(K(erg)) in differentiated NG108-15 cells; dynorphin A(1-13) did not reverse Mtd-induced inhibition of I(K(erg)). This study shows that Mtd has a depressant effect on I(K(erg)), and suggests its ability to affect membrane excitability and prolactin secretion. The cyclization of Mtd, in which EDDP and EMDP are formed, tends to be critical in removal of the Mtd binding to erg K+ channel.     

The effect of a secreted form of β-amyloid-precursor protein on intracellular Ca2+ increase in rat cultured hippocampal neurones

1. The effects of secreted forms of β-amyloid-precursor proteins (APP^Ss) on the intracellular Ca²⁺ concentration ([Ca²⁺]_i) were investigated in rat cultured hippocampal neurones. APP695^S, a secretory form of APP695, attenuated the increase in [Ca²⁺]_i evoked by glutamate. In addition, APP695^S itself evoked an increase in [Ca²⁺]_i in 1 or 2 day-cultured hippocampal cells, but not in 7 to 13 day-cultured cells.
2. Eighty-one percent of neurones which were immunocytochemically positive for microtubule-associated protein 2 responded to APP695^S with an increase in [Ca²⁺]_i.
3. APP695^S induced a transient rise in [Ca²⁺]_i even in the absence of extracellular Ca²⁺ and produced an elevation in inositol-1,4,5-trisphosphate (IP₃) in a concentration-dependent manner from 100 to 500 ng ml⁻¹. In the presence of extracellular Ca²⁺, APP695^S caused a transient rise in [Ca²⁺]_i followed by a sustained phase at high [Ca²⁺]_i, suggesting Ca²⁺ entry from the extracellular space.
4. The [Ca²⁺]_i elevation was mimicked by amino terminal peptides of APP^S, but not by carboxy terminal peptides.
5. These results taken together suggest that APP695^S induces an increase in [Ca²⁺]_i in hippocampal neurones through an IP₃-dependent mechanism that changes according to the stage of development.

     

Antagonistic actions of S(−)-Bay K 8644 on cyclic nucleotide-induced inhibition of voltage-dependent Ba2+ currents in guinea pig gastric antrum

(±)-Bay K 8644, a conventional racemic mixture of Bay K 8644, is widely used as an L-type Ca²⁺ channel agonist. Although interactions between Bay K 8644 and cyclic nucleotide have been described, they have not been properly characterized. We have investigated whether two optical isomers of Bay K 8644 (i.e., R(+)- and S(−)-Bay K 8644) modify cyclic nucleotide (cAMP and cGMP)-induced inhibitory effects on nifedipine-sensitive voltage-dependent Ba²⁺ currents (I _Ba) recorded from guinea pig gastric myocytes. Conventional whole-cell recordings were used to compare the effects of R(+)-Bay K 8644 and S(−)-Bay K 8644 on I _Ba. S(−)-Bay K 8644 enhanced the peak amplitude of I _Ba evoked by depolarizing pulses to +10 mV from a holding potential of −70 mV in a concentration-dependent manner (EC₅₀ = 32 nM), while R(+)-Bay K 8644 inhibited I _Ba (IC₅₀ = 975 nM). When R(+)-Bay K 8644 (0.5 μM) was applied, I _Ba was suppressed to 71 ± 10% of control. In the presence of R(+)-Bay K 8644 (0.5 μM), additional application of forskolin and sodium nitroprusside (SNP) further inhibited I _Ba. Conversely, in the presence of S(−)-Bay K 8644 (0.5 μM), subsequent application of forskolin and SNP did not affect I _Ba. Similarly, in the presence of 0.5 μM S(−)-Bay K 8644, db-cAMP and 8-Br-cGMP had no effect on I _Ba. These results indicate that S(−)-Bay K 8644, but not R(+)-Bay K 8644, can prevent the inhibitory actions of two distinct cyclic nucleotide pathways on I _Ba in gastric myocytes of the guinea pig antrum.     

Effect of Device Design on the Aerosolization of a Carrier-Based Dry Powder Inhaler—a Case Study on Aerolizer® Foradile®

The objective of this study is to investigate the effect of device design of the Aerolizer^® on the aerosolization of a carrier-based dry powder inhaler formulation (Foradile^®). The Aerolizer was modified by reducing the air inlet size and mouthpiece length to 1/3 of the original dimensions, or by increasing the grid voidage. Aerosolization of the powder formulation was assessed on a multi-stage liquid impinger at air flow rates of 30, 60, and 100 L/min. Coupled CFD-DEM simulations were performed to investigate the air flow pattern and particle impaction. There was no significant difference in the aerosolization behavior between the original and 1/3 mouthpiece length devices. Significant increases in FPF total and FPF emitted were demonstrated when the inlet size was reduced, and the results were explained by the increases in air velocity and turbulence from the CFD analysis. No significant differences were shown in FPF total and FPF emitted when the grid voidage was increased, but more drugs were found to deposit in induction port and to a lesser extent, the mouthpiece. This was supported by the CFD-DEM analysis which showed the particle–device collisions mainly occurred in the inhaler chamber, and the cross-grid design increased the particle–device collisions on both mouthpiece and induction port. The air inlet size and grid structure of the Aerolizer^® were found to impact significantly on the aerosolization of the carrier-based powder.     

Impact of Participation on a Solid Organ Transplant Team on Student Pharmacists’ Perceptions of Interprofessional Roles

Objective. To examine student pharmacists’ perceptions of interprofessional roles before and after completing an advanced pharmacy practice experience on solid organ transplantation.Methods. Student pharmacists across the United States participating in an APPE on a solid organ transplant team completed an online pre- and post-APPE survey instrument examining perceptions of interprofessional roles, communication, and teamwork.Results. Student pharmacists’ scores on interprofessionalism increased significantly on 17 of 22 items. Positive changes were seen in the interprofessional education core competency areas of roles and responsibilities, interprofessional communication, and teams and teamwork.Conclusion. Student pharmacist participation in interprofessional clinical APPEs can positively influence their professional development as they prepare to become members of multi-disciplinary teams in the healthcare workforce.     

Is the effect of smoking on rosacea still somewhat of a mystery?

Context: Rosacea is an inflammatory skin disease with a chronic course. In the past, the association between rosacea and smoking was examined only in a few studies.

Objective: The objective of this study is to investigate the prevalence and the influence of smoking in rosacea patients.

Materials and methods: This prospective cross-sectional study includes 200 rosacea patients and 200 age- and gender-matched rosacea-free controls. Using National Rosacea Society Expert Committee classification, we divided patients into three subgroups as having erythematotelangiectatic (ETR), papulopustular (PPR), and phymatous rosacea (PhR). Demographic data, risk factors, and smoking habits were recorded.

Results: In multivariate analysis, the prevalence of smoking was significantly higher (66%) among patients compared with controls. ETR subtype (43.5%) was found to be significantly higher among active smokers (p?<?0.001). Considering the risk factors, caffeine intake and alcohol consumption could not be evaluated because of their never or rarely intake. Whereas rates of photosensitive skin type and positive family history were significantly prominent in ETR patients (p?<?0.001). While PhR was mostly detected in men who are very old, a significant tendency was found to develop ETR in women.

Conclusion: While a significantly increased risk of developing rosacea among smokers was observed in this study, ETR seems to be the disease of active smokers. Further studies are required for better understanding of the association between rosacea and smoking.     

The antiepileptic effect of Centella asiatica on the activities of Na+/K+, Mg2+ and Ca2+-ATPases in rat brain during pentylenetetrazol�Cinduced epilepsy

Background:

To study the anticonvulsant effect of different extracts of Centella asiatica (CA) in male albino rats with reference to Na⁺/K⁺, Mg²⁺ and Ca²⁺-ATPase activities.

Materials and Methods:

Male Wistar rats (150±25 g b.w.) were divided into seven groups of six each i.e. (a) control rats treated with saline, (b) pentylenetetrazol (PTZ)-induced epileptic group (60 mg/kg, i.p.), (c) epileptic group pretreated with n-hexane extract (n-HE), (d) epileptic group pretreated with chloroform extract (CE), (e) epileptic group pretreated with ethyl acetate extract (EAE), (f) epileptic group pretreated with n-butanol extract (n-BE), and (g) epileptic group pretreated with aqueous extract (AE).

Results:

The activities of three ATPases were decreased in different regions of brain during PTZ-induced epilepsy and were increased in epileptic rats pretreated with different extracts of CA except AE.

Conclusion:

The extracts of C. asiatica, except AE, possess anticonvulsant and neuroprotective activity and thus can be used for effective management in treatment of epileptic seizures.     

Effects of σ ligands on the nociceptin/orphanin FQ receptor co-expressed with the G-protein-activated K+ channel in Xenopus oocytes

Taking advantage of the functional coupling of the nociceptin/orphanin FQ receptor with the G-protein-activated inwardly rectifying K⁺ (GIRK) channel, we investigated the effects of various σ ligands on the nociceptin/orphanin FQ receptor in Xenopus oocytes co-injected with the cloned nociceptin/orphanin FQ receptor and GIRK1 mRNAs. Carbetapentane and rimcazole, which induced no current response at 100 μM, reversibly suppressed the inward K⁺ current responses induced by nociceptin in a concentration-dependent manner, and the IC₅₀ values (μM) for these compounds were 9.0 and 12.6, respectively. (±)-N-allylnormetazocine, (+)-cyclazocine, (+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine and 1,3-di-(2-tolyl)guanidine, at 100 μM, had no effect on the receptor. These results suggest that carbetapentane and rimcazole act as antagonists at the nociceptin/orphanin FQ receptor and may be involved in pain regulation.     

Influence of PEI as a core modifying agent on PLGA microspheres of PGE₁, a pulmonary selective vasodilator

This study tests the hypothesis that large porous poly (lactic-co-glycolic acid) (PLGA) microparticles modified with polyethyleneimine (PEI) are viable carriers for pulmonary delivery of prostaglandin E(1) (PGE(1)) used in the treatment of pulmonary arterial hypertension (PAH), a pulmonary vascular disorder. The particles were prepared by a double-emulsion solvent evaporation method with PEI-25 kDa in the internal aqueous phase to produce an osmotic pressure gradient. Polyvinyl alcohol (PVA) was used for external coating of the particles. The particles were examined for morphology, size, aerodynamic diameter, surface area, pore volume and in-vitro release profiles. Particles with optimal properties for inhalation were tested for in-vivo pulmonary absorption, metabolic stability in rat lung homogenates, and acute toxicity in rat bronchoalveolar lavage fluid and respiratory epithelial cells, Calu-3. The micromeritic data indicated that the PEI-modified particles of PGE(1) are optimal for inhalation. Incorporation of PEI in the formulations resulted in an increased entrapment efficiency - 83.26 ± 3.04% for particles with 1% PVA and 95.48 ± 0.46% for particles with 2% PVA. The amount of cumulative drug released into the simulated interstitial lung fluid was between 50.8 ± 0.76% and 55.36 ± 0.06%. A remarkable extension of the circulation half-life up to 6.0-6.5h was observed when the formulations were administered via the lungs. The metabolic stability and toxicity studies showed that the optimized formulations were stable at physiological conditions and relatively safe to the lungs and respiratory epithelium. Overall, this study demonstrates that large porous inhalable polymeric microparticles can be a feasible option for non-invasive and controlled release of PGE(1) for treatment of PAH.     

Influence of a ward-based pharmacist on the medication quality of geriatric inpatients: a before–after study

Background Despite several international studies demonstrating that ward-based pharmacists improve medication quality, ward pharmacists are not generally established in German hospitals. Aim We assessed the effect of a ward-based clinical pharmacist on the medication quality of geriatric inpatients in a German university hospital. Method The before-after study with a historic control group was conducted on the geriatric ward. During the control phase, patients received standard care without the involvement of a pharmacist. The intervention consisted of a clinical pharmacist providing pharmaceutical care from admission to discharge. Medication quality was measured on admission and discharge using the Medication Appropriateness Index (MAI). A linear regression analysis was conducted to calculate the influence of the intervention on the MAI. Results Patients in the intervention group (n?=?152, mean 83 years) were older and took more drugs at admission compared to the control group (n?=?159, 81 years). For both groups, the MAI per patient improved significantly from admission to discharge. Although the intervention did not influence the summated MAI score per patient, the intervention significantly reduced the MAI criteria Dosage (p?=?0.006), Correct Directions (p?=?0.016) and Practical Directions (p?=?0.004) as well as the proportion of overall inappropriate MAI ratings (at least 1 of 9 criteria inappropriate) (p?=?0.015). Conclusion Although medication quality was already high in the control group, a ward-based clinical pharmacist could contribute meaningfully to the medication quality on an acute geriatric ward.

     

What should be considered on design of a colon-specific prodrug?

Importance of the field: Generally, a prodrug, a pharmacologically inactive derivative of an active drug, is designed to modulate pharmacokinetic properties of the parent drug. Targeted distribution of an orally administered drug at the large intestine confers therapeutic advantages on treatment of colonic diseases, peptide and protein therapy and chronotherapy.

Areas covered in this review: To achieve such distribution control in the gastrointestinal tract, the adoption of the prodrug concept gives birth to a colon-specific prodrug. The requirement for a prodrug to be colon-specific is described along with the necessary and sufficient conditions of drugs for conversion to a colon-specific prodrug. The known and previously unnoticed factors that negatively influence therapeutic activity and reproducibility of a colon-specific prodrug are presented with suggestions to minimize the negative influence.

What the reader will gain: This review provides tactics to satisfy the requirements for being colon-specific and the potential strategies to circumvent obstacles in developing an efficient colon-specific prodrug.

Take home message: On design of a colon-specific prodrug, one should take into consideration not only delivery of a drug to the target site, but also the therapeutic effectiveness there.     

Pleiotropic effects of statins on the treatment of chronic periodontitis – a systematic review

Aim

Statins are inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase and are an important group of hypolipidaemic drugs, widely used in the treatment of hypercholesterolaemia and cardiovascular disease. Some studies have shown that statins are able to modulate inflammation and alveolar bone loss.

Methods

In order to evaluate whether statins could influence periodontal treatment, improving the clinical and radiographic parameters in chronic periodontitis, a systematic review was conducted in the databases PUBMED and BIREME, searching for articles in English and Portuguese, published between the years 2004 and 2014, using the combined keywords statin, periodontal disease, periodontitis and alveolar bone. Studies regarding the treatment of chronic periodontitis in humans, blind or double-blind, retrospective cohort or randomized controlled trials that used statins topically or systemically were selected.

Results

Statins have important anti-inflammatory and immune effects, reducing levels of C-reactive protein and matrix metalloproteinases and their intermediate products, such as tumour necrosis factor-α, and are also able to inhibit the adhesion and extravasation of leukocytes, which block the co-stimulation of T cells. Statins reduce bone resorption by inhibiting osteoclast formation and lead to increased apoptosis of these cells. The effect of statins on bone formation is related to the increased gene expression of bone morphogenetic protein in osteoblasts.

Conclusion

Although we found biological mechanisms and clinical results that show lower alveolar bone loss and reduction of clinical signs of inflammation, further studies are needed to evaluate the clinical applicability of statins in the routine treatment of chronic periodontitis.     

Effects of heparin on growth factor-induced mitogenic and proliferative responses of rat pulmonary a

目的：探讨肝素是否能抑制生长因子诱导的大鼠肺动脉平滑肌细胞（ＰＡＳＭＣ）分裂和增殖．方法：应用含１０％ＦＢＳ的Ｍ１９９培养液培养大鼠ＰＡＳＭＣ．细胞分裂及细胞增殖分别用［ｍｅｔｈｙｌ３Ｈ］ＴｄＲ和细胞计数监测．结果：ＦＢＳ（１０％），以及ＦＢＳ（１％）与ＰＤＧＦ（５０μｇ·Ｌ－１），ＦＧＦ（５０μｇ·Ｌ－１），或ＩＬ１α（１００ｎｇ·Ｌ－１）联合应用均能增加大鼠ＰＡＳＭＣ分裂．肝素（１００ｍｇ·Ｌ－１）抑制１０％ＦＢＳ诱导的大鼠ＰＡＳＭＣ增殖（２８％±６％）和胸腺嘧啶摄取反应（２７％±７％），抑制ＦＢＳ（１％）与ＰＤＧＦ（５０μｇ·Ｌ－１），ＦＧＦ（５０μｇ·Ｌ－１），或ＩＬ１α（１００ｎｇ·Ｌ－１）联用诱导的大鼠ＰＡＳＭＣ增殖（２５％±６％，２７％±７％，２０％±４％），以及胸腺嘧啶摄取反应（２３％±７％，２６％±６％，２０％±６％）．结论：肝素抑制生长因子诱导的大鼠ＰＡＳＭＣ的分裂与增殖．     

Differential antagonism by naloxone benzoylhydrazone of the activation of inward rectifying K+ channels by nociceptin and a µ-opioid in rat periaqueductal grey slices

A novel receptor, the opioid receptor-like orphan receptor (ORL1), is homologous to, but distinct from, classical opioid receptors. Although initially developed as an opioid receptor ligand, naloxone benzoylhydrazone (NalBzOH) is one of the few antagonists at ORL1. The present electrophysiological study of the effects of NalBzOH on the activation of ORL1 and mu-opioid receptors was performed in brain slices of the ventrolateral periaqueductal grey (PAG), a crucial site for opioid-induced supraspinal analgesia. Both orphanin FQ/nociceptin (OFQ/N), an ORL1 agonist, and [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO), a mu-opioid receptor agonist, activated inwardly rectifying K+ (Kir) channels in the ventrolateral PAG. Of the neurons tested, 96% responded to OFQ/N, but only 65% to DAMGO. NalBzOH (3-30 microM) antagonized the effect of OFQ/N competitively with a pA2 of 5.67. NalBzOH also antagonized, but more potently and non-competitively, the effect of DAMGO. In contrast, NalBzOH did not affect baclofen-induced activation of Kir channels. NalBzOH alone, at concentrations up to 30 microM, had little effect on this inwardly rectifying channel. It is concluded that NalBzOH antagonizes the activation of Kir channels mediated by both ORL1 and mu-opioid receptors in the ventrolateral PAG. It acts not only as a competitive antagonist at ORL1, but also as a more potent and non-competitive antagonist at mu-opioid receptors.     

Alcohol effects on movement-related potentials: a measure of impulsivity?

OBJECTIVE: To assess the effects of acute alcohol intoxication on lateralized readiness potential (LRP), a central measure of movement-related brain activity, and the potential association of such effects with personality measures. METHOD: Male volunteers (N = 12) alternated responding hands during a "go/no go" verbal recognition task across all four sessions of the balanced placebo design in which beverage content (either juice only or a vodka and juice mixture that raised the average blood alcohol concentration to 0.045%) was crossed with instructions as to beverage content. RESULTS: Whereas the instructions had no effect on behavioral (response accuracy and reaction time) and physiological (LRP) measures, alcohol decreased reaction times adjusted for psychometer speed. As expected, large LRPs were recorded on "go" trials and were not affected by the beverage. However, the "no go" words that did not require and did not evoke motor responses, also evoked significant LRPs under alcohol but not placebo. Since only trials with correct responses and correct abstentions from responses were included in the averages, the motor preparation was not completed and was terminated before the motor response on "no go" trials. Similarly, there was a decrease in spectral power of the movement-related mu-rhythm on "no go" trials under alcohol. CONCLUSIONS: Alcohol may result in disinhibition such that the "response execution" process is activated based on very preliminary stimulus evaluation. This alcohol-induced brain activity signaling premature motor preparation exhibited correlation trends with personality traits related to impulsivity, hyperactivity and antisocial tendencies, thus concurring with other evidence that indicates commonalities between alcoholism and impulsivity, disinhibition and antisocial behaviors. The LRP on "no go" trials could potentially be used as a psychological index of the impulsiveness induced by alcohol intoxication.