Brain Extracellular γ-hydroxybutyrate Concentrations are Decreased by L-lactate in Rats: Role in the Treatment of Overdoses

Purpose

L-lactate represents a potential treatment for GHB overdose by inhibiting GHB renal reabsorption mediated by monocarboxylate transporters. Our objective was to assess the dose-dependence of L-lactate treatment, with and without D-mannitol, on GHB toxicokinetics/toxicodynamics (TK/TD).

Methods

Rats were administered GHB 600 mg/kg i.v. with L-lactate (low and high doses), D-mannitol, or L-lactate (low dose) with D-mannitol. GHB-induced sleep time and GHB plasma, urine and brain extracellular fluid (ECF) concentrations (by LC/MS/MS) were determined. The effect of L-lactate and D-mannitol on the uptake and efflux of GHB was assessed in rat brain endothelial RBE4 cells.

Results

L-lactate treatment increased GHB renal clearance from 1.4?±?0.1 ml/min/kg (control) to 2.4?±?0.2 and 4.7?±?0.5 ml/min/kg after low and high doses, respectively, and reduced brain ECF AUC values to 65 and 25% of control. Sleep time was decreased from 137?±?12 min (control) to 91?±?16 and 55?±?5 min (low and high L-lactate, respectively). D-mannitol did not alter GHB TK/TD and did not alter L-lactate’s effects on GHB TK/TD. L-lactate, but not D-mannitol, inhibited GHB uptake, and increased GHB efflux from RBE4 cells.

Conclusions

L-lactate decreases plasma and brain ECF concentrations of GHB, decreasing sedative/hypnotic effects.     

Specific Role of VTA Dopamine Neuronal Firing Rates and Morphology in the Reversal of Anxiety-Related, but not Depression-Related Behavior in the Clock��19 Mouse Model of Mania

Lithium has been used extensively for mood stabilization, and it is particularly efficacious in the treatment of bipolar mania. Like other drugs used in the treatment of psychiatric diseases, it has little effect on the mood of healthy individuals. Our previous studies found that mice with a mutation in the Clock gene (ClockΔ19) have a complete behavioral profile that is very similar to human mania, which can be reversed with chronic lithium treatment. However, the cellular and physiological effects that underlie its targeted therapeutic efficacy remain unknown. Here we find that ClockΔ19 mice have an increase in dopaminergic activity in the ventral tegmental area (VTA), and that lithium treatment selectively reduces the firing rate in the mutant mice with no effect on activity in wild-type mice. Furthermore, lithium treatment reduces nucleus accumbens (NAc) dopamine levels selectively in the mutant mice. The increased dopaminergic activity in the Clock mutants is associated with cell volume changes in dopamine neurons, which are also rescued by lithium treatment. To determine the role of dopaminergic activity and morphological changes in dopamine neurons in manic-like behavior, we manipulated the excitability of these neurons by overexpressing an inwardly rectifying potassium channel subunit (Kir2.1) selectively in the VTA of ClockΔ19 mice and wild-type mice using viral-mediated gene transfer. Introduction of this channel mimics the effects of lithium treatment on the firing rate of dopamine neurons in ClockΔ19 mice and leads to a similar change in dopamine cell volume. Furthermore, reduction of dopaminergic firing rates in ClockΔ19 animals results in a normalization of locomotor- and anxiety-related behavior that is very similar to lithium treatment; however, it is not sufficient to reverse depression-related behavior. These results suggest that abnormalities in dopamine cell firing and associated morphology underlie alterations in anxiety-related behavior in bipolar mania, and that the therapeutic effects of lithium come from a reversal of these abnormal phenotypes.     

Estradiol and testosterone modulate the anesthetic action of the GABA-A agonist THIP,but not of the neurosteroid 3α,5β-pregnanolone in the rat

Rationale As sex steroids modify the number and distribution of brain -aminobutyric acid (GABA)_A receptor subunits, we investigated the potential modulation of anesthesia, induced by agents acting on the GABA_A receptor, by estrogen and androgen.Objectives To assess possible effects of sex and hormonal condition (i.e., intact vs castrate; estradiol vs testosterone treatment) on the anesthetic effect of a GABA_A agonist, THIP (4,5,6,7-tetrahydroisoxazolo[5,4,-c]pyridin-3-ol hydrochloride), and an allosteric modulator of the GABA_A receptor: 3-hydroxy-5-pregnan-20-one (epipregnanolone).Methods The potencies of THIP and epipregnanolone for inducing loss of the righting response were compared between: (a) female and male rats; (b) intact and castrated animals of each sex; (c) untreated castrates and castrates given estradiol or testosterone.Results Sex and endocrine condition influenced sensitivity to i.v. THIP for the induction of anesthesia. ED₅₀ values were: gonadectomized females, 80 mg/kg > intact males, 50 mg/kg > proestrous females, 35 mg/kg > gonadectomized males, 28 mg/kg. Estradiol benzoate (EB; 3 g/day for 5 days) significantly increased THIP sensitivity in gonadectomized females: THIP + EB: ED₅₀=26 mg/kg vs THIP + sesame oil: ED₅₀=94 mg/kg, while testosterone propionate (TP; 10 mg injected 24 h before THIP) decreased THIP sensitivity in orchidectomized males when compared with vehicle-injected animals (ED₅₀=72 mg/kg vs 22 mg/kg, respectively).Conclusions Results suggest that estrogen increases the density or availability of GABA_A receptor subtypes on which THIP acts, while testosterone exerts the opposite effect. Neither sex nor gonadal condition influenced the anesthetic action of epipregnanolone as a similar potency was found in intact and in gonadectomized males and females.     

α-Lipoic Acid and Superoxide Dismutase in the Management of Chronic Neck Pain: A Prospective Randomized Study

Background and Objective

Since oxidative stress plays a pathogenetic role in chronic neck pain (CNP), we investigated whether a combination of α-lipoic acid (ALA) and superoxide dismutase (SOD) might improve pain control and the efficacy of physiotherapy (“multimodal therapy”) in patients with CNP.

Setting

This study was conducted in the Rehabilitation Unit of the Department of Surgical and Oncological Sciences at the University Policlinic in Palermo, Italy.

Design and Patients

This was a prospective, randomized, open study in outpatients.

Intervention

Patients randomly received either physiotherapy alone (group 2; n = 45) or a combination of ALA 600 mg and SOD 140 IU daily in addition to physiotherapy (group 1; n = 51), for 60 days. Pain was assessed by a visual analogue scale (VAS) and a modified Neck Pain Questionnaire (mNPQ). Treatment compliance and safety were also evaluated.

Results

Both groups experienced a significant reduction in the VAS and mNPQ scores after 1 month; however, while no further improvement was observed in group 2 at 60 days, group 1 showed a further VAS reduction (p < 0.001). In addition, in the mNPQ at 60 days, more patients in group 1 than in group 2 reported that their neck pain was improved (p < 0.01), and they showed greater compliance with prescribed physiotherapy (p = 0.048). No drug reaction was observed.

Conclusion

Use of ALA/SOD in combination with physiotherapy may be a useful approach to CNP, being antioxidants that act on nerve inflammation and disease progression.

Clinical Rehabilitation Impact

These preliminary observations suggest that some interesting goals (better pain control and physical wellbeing) can be achieved by multimodal therapy in CNP patients.     

Long-Term Ketamine Self-Injections in Major Depressive Disorder: Focus on Tolerance in Ketamine’s Antidepressant Response and the Development of Ketamine Addiction

Abstract

Sub-anaesthetic ketamine is of special interest for depression research due to its rapid and potent but short-lived antidepressant response (after-effect). The presented case is the first one in the literature which deals in detail with the transfer from ketamine’s antidepressant action to ketamine addiction. A 50-year-old anaesthetic nurse, who had never been treated with antidepressants before, started with self-injecting ketamine racemate 50 mg IM once a week to cope with her major depression. She continuously stole ketamine from hospital stocks. Due to a gradually developing tolerance to ketamine’s antidepressant action, she stepwise increased dose and frequency of ketamine self-injections up to daily 2 g IM (three-fold her anaesthetic dose) over six months. This was accompanied by the development of ketamine addiction, loss of consciousness, dissociative immobility, and amnesia. Inpatient detoxification treatment was characterized by a strong craving for ketamine and, later on, by the occurrence of a severe depressive episode remitting on venlafaxine. A 14-week follow-up documented a normal condition without any ketamine sequelae, such as craving, psychosis, depression, or cognitive abnormalities. Thus, awareness of ketamine addiction potential, even in patients who received ketamine for antidepressant purposes, is important.     

Blockade of dopamine receptors reverses the behavioral effects of endogenous enkephalins in the Nucleus caudatus but not in the Nucleus accumbens: differential involvement of δ and μ opioid receptors

We have previously (Daugé et al. 1988) demonstrated that injection of the agonist [d-Ala², MePhe⁴, Gly-ol⁵]-enkephalin (DAGO) or the agonist [d-Thr², Leu⁵]-enkephalyl-Thr⁶ (DTLET) into the rat Nucleus accumbens (N.Acc.), or Nuceeus caudatus (N.Caud.) induced a hypoactivity followed by hyperactivity 150 min later in the case of the agonist and a hyperactivity in the case of the agonist. Moreover, naloxone reversible delta-type responses were obtained by local infusion of kelatorphan, ([(R)-3(N-hydroxylcarboxamido-2-benzylpropanoyl)-l-alanine]), a complete inhibitor of enkephalin catabolism, suggesting a tonic control of the behavioral activity of rat by the endogenous opioid peptides. In this work, the putative involvement of the dopaminergic system in these behavioral responses was investigated by using the DA antagonist thioproperazine. In the N.Acc., the behavioral effects of kelatorphan, or of or agonists were not altered by thioproperazine-induced blockade of dopamine receptors. In contrast, the hyperactivity produced by DTLET or by kelatorphan in the N.Caud. was reversed by thioproperazine while the time-dependent biphasic effect resulting from DAGO injection remained unaffected by the DA antagonist. This blocking effect of thioproperazine is in agreement with the previously described -selective enhancement of the release of newly synthesized DA in the striatum but not in the N.Acc.     

Chronic food restriction in rats augments the central rewarding effect of cocaine and the δ1 opioid agonist, DPDPE, but not the δ2 agonist, deltorphin-II

RATIONALE: There is some, albeit conflicting, evidence that 5-HT3 receptors might be involved in the actions of abused stimulants. Most studies have focussed on examinations of 5-HT3 antagonists; this might be due to a lack of high-affinity 5-HT3 agonists that readily penetrate the blood-brain barrier. OBJECTIVES: N-(3-Chlorophenyl) guanidine (MD-354) is a member of a novel class of 5-HT3 ligands developed in our laboratories. We have previously demonstrated that MD-354 can exert agonist effects and now further explore this action. METHODS: Rats (n=9) were trained to discriminate 2 mg/kg MD-354 from saline vehicle in a two-lever drug discrimination task (VI-15 s schedule of reinforcement). The actions of agents with 5-HT3 character were evaluated. The emetic and antiemetic actions of MD-354 were also examined using the shrew as test subject. RESULTS: Various agents with demonstrated 5-HT3 agonist properties substituted for the MD-354 stimulus (MD-354 ED50=0.5 mg/kg): quipazine (ED50=0.2 mg/kg), meta-chlorophenylbiguanide (mCPBG, ED50=1.4 mg/kg), 2-methyl 5-HT (ED50=4.5 mg/kg), 1-(2-naphthyl)biguanide (2-NBG, ED50=1.9 mg/kg), and N-(2-naphthyl)guanidine (2-NG, ED50=0.7 mg/kg). Administration of the training dose of MD-354 in combination with the 5-HT3 antagonists zacopride and tropisetron resulted in stimulus antagonism (AD50=0.02 mg/kg); administered alone, however, zacopride engendered 81% MD-354-appropriate responding (ED50=0.03 mg/kg). MD-354 was shown to produce an emetic effect in the shrew at very high doses (i.e., 40 mg/kg); however, when administered in combination with cisplatin, MD-354 behaved as an antiemetic agent at 10 mg/kg. CONCLUSION: Taken together, the results indicate that MD-354 is a 5-HT3 agonist and that it might be an agent with partial agonist activity.     

Comparison of Two Forms of Loperamide–Simeticone and a Probiotic Yeast (Saccharomyces boulardii) in the Treatment of Acute Diarrhoea in Adults: A Randomised Non-Inferiority Clinical Trial

Background

Acute diarrhoea is a frequent health problem in both travellers and residents that has a social and economic impact. This study compared the efficacy and tolerability of two loperamide–simeticone formulations and a Saccharomyces boulardii capsule as symptomatic treatment.

Methods

This was a prospective, randomised, single (investigator)-blind, three-arm, parallel group, non-inferiority clinical trial in adult subjects with acute diarrhoea at clinics in Mexico and India, with allocation to a loperamide–simeticone 2/125 mg caplet or chewable tablet (maximum eight in 48 h) or S. boulardii (250 mg twice daily for 5 days).

Outcome Measures

The primary outcome measure was the number of unformed stools between 0 and 24 h following the initial dose of study medication (NUS 0–24). The secondary outcome measures were time to last unformed stool (TLUS), time to complete relief of diarrhoea (TCRD), time to complete relief of abdominal discomfort (TCRAD) and the subject’s evaluation of treatment effectiveness. Follow-up endpoints at 7 days were feeling of complete wellness; stool passed since final study visit; and continued or recurrent diarrhoea.

Subjects

In this study, 415 subjects were randomised to either a loperamide–simeticone caplet (n = 139), loperamide–simeticone chewable tablet (n = 139) or S. boulardii capsule (n = 137) and were included in the intention-to-treat analysis.

Results

With regards to mean NUS 0–24, the loperamide–simeticone caplet was non-inferior to loperamide–simeticone tablets (3.4 vs. 3.3; one-sided 97.5 % confidence interval ≤0.5), with both significantly lower than S. boulardii (4.3; p < 0.001). The loperamide–simeticone groups had a shorter median TLUS [14.9 and 14.0 vs. 28.5 h (loperamide–simeticone caplet and chewable tablet groups, respectively, vs. S. boulardii); p < 0.001], TCRD (26.0 and 26.0 vs. 45.8 h; p < 0.001) and TCRAD (12.2 and 12.0 vs. 23.9 h; p < 0.005) than S. boulardii. Treatment effectiveness for overall illness, diarrhoea and abdominal discomfort relief was greater (p < 0.001) in the loperamide–simeticone groups than with S. boulardii. At 7-day follow-up most subjects reported passing stool at least once since the final study visit (loperamide–simeticone caplet 94.1 %, loperamide–simeticone chewable tablet 94.8 %, S. boulardii 97.0 %), did not experience continued or recurrent diarrhoea [loperamide–simeticone caplet 3.7 % (p < 0.03 vs. S. boulardii), loperamide–simeticone chewable tablet 3.7 %, S. boulardii 5.7 %] and felt completely well [loperamide–simeticone caplet 96.3 % (p < 0.02 vs. S. boulardii), loperamide–simeticone chewable tablet 96.3 % (p < 0.02 vs. S. boulardii), S. boulardii 88.6 %]. All treatments were well-tolerated with few adverse events.

Conclusions

The loperamide–simeticone caplet was non-inferior to the original loperamide–simeticone chewable tablet formulation; both formulations can be expected to demonstrate similar clinical efficacy in the relief of symptoms of acute diarrhoea. Both loperamide–simeticone formulations were superior to the S. boulardii capsule in the primary and secondary endpoints.

Clinical Trial Registration

ClinicalTrials.gov identifier {"type":"clinical-trial","attrs":{"text":"NCT00807326","term_id":"NCT00807326"}}NCT00807326.     

Nicotine reverses the enhanced renal vasodilator capacity in endotoxic rats: Role of α7/α4β2 nAChRs and HSP70

BackgroundNicotine alleviates renal inflammation and injury induced by endotoxemia. This study investigated (i) the nicotine modulation of hemodynamic and renal vasodilatory responses to endotoxemia in rats, and (ii) roles of α7 or α4β2-nAChRs and related HSP70/TNFα/iNOS signaling in the interaction.MethodsEndotoxemia was induced by ip lipopolysaccharide (5 mg/kg/day, for 2 days) and changes in systolic blood pressure and vasodilator responsiveness of isolated perfused kidney to acetylcholine or 5′-N-ethylcarboxamidoadenosine (NECA, adenosine receptor agonist) were evaluated.ResultsLipopolysaccharide had no effect on serum creatinine, reduced blood pressure, and increased renal vasodilations induced by acetylcholine or NECA in male and female preparations. Immunohistochemical analyses showed that lipopolysaccharide reduced renal HSP70 expression, but increased α7-nAChRs, α4β2-nAChRs and iNOS expressions. The co-administration of aminoguanidine (iNOS inhibitor), pentoxifylline (TNFα inhibitor), or nicotine attenuated lipopolysaccharide mediation of renal vasodilations and elevations in α7/α4β2-nAChR and iNOS expressions. Nicotine also reversed the downregulating effect of lipopolysaccharide on HSP70 expression. α7-nAChRs (methyllycaconitine citrate, MLA) or α4β2-nAChRs (dihydro-β-erythroidine, DHβE) blockade potentiated the lipopolysaccharide enhancement of renal vasodilations, and abolished the depressant effect of nicotine on lipopolysaccharide responses. A similar abolition of nicotine effects was seen after HSP70 inhibition by quercetin. Alternatively, lipopolysaccharide hypotension was eliminated in rats treated with DHβE/nicotine or quercetin/nicotine regimen in contrast to no effect for nicotine alone or combined with MLA.ConclusionsThese findings establish that nicotine offsets lipopolysaccharide facilitation of renal vasodilations possibly through a crosstalk between HSP70 and nAChRs of the α7 and α4β2 types.     

Activation of a nonspecific cation current in rat cultured retinal pigment epithelial cells: involvement of a Gαi subunit protein and the mitogen-activated protein kinase signalling pathway

1. Whole-cell patch-clamp recording techniques were used to investigate the G protein subtype and related signalling molecules involved in activation of a nonspecific cation (NSC) current in rat cultured retinal pigment epithelial (RPE) cells.
2. Under control conditions, in 130 mM NaCl with K⁺ aspartate in the pipette, cytosolic dialysis with guanosine-5′-O-(3-triphosphate) (GTPγS, 0.1 mM) activated a large non-inactivating NSC current in 80% of the cells recorded from.
3. Loading RPE cells with antibodies (10 μg-ml⁻¹) against the α subunit of all PTX-sensitive G proteins (G_αi/o/t/z) reduced NSC current activation to 11%, while loading RPE cells with antibodies directed specifically against the α subunits of the G_i subclass (G_αi-3) completely abolished current activation. In RPE cells loaded with anti-G_αs activation of the NSC current was unaffected.
4. Investigation of the potential downstream mediators in the G_αi NSC channel pathway revealed that activation of the cation conductance was unaffected by treatment of RPE cells with the selective protein kinase C inhibitor GF 109203X (3 μM) or the selective CaM kinase II inhibitor KN-93 (50 μM). However, NSC current activation was delayed and the current amplitude reduced in the presence of the nonselective kinase inhibitor H-7 (100 μM) or the selective inhibitor of MAPKK (MEK) activation, PD 98059 (50 μM).
5. In the absence of GTPγS, the NSC current was not activated by superfusion of the cells with the cyclic GMP kinase activator dibutyryl-cyclic GMP or with the adenylate cyclase activator forskolin.
6. These results support the involvement of a G protein of the G_αi subclass in the activation of a NSC current in rat RPE cells, and suggest a potential modulatory role for MAP kinase-dependent phosphorylation in current regulation.