Efficacy and safety of intravenous fosphenytoin for patients with acute herpes zoster-associated pain: A placebo-controlled randomized trial

Acute zoster-associated pain develops in most patients with herpes zoster. Nonopioid analgesics are usually used to treat acute zoster-associated pain but are frequently ineffective. We administered intravenous fosphenytoin, the prodrug of phenytoin, to patients with acute zoster-associated pain to examine its analgesic efficacy and safety. At 13 medical institutions in Japan, we conducted a phase II, double-blind, placebo-controlled, randomized trial of intravenous fosphenytoin in Japanese inpatients with acute zoster-associated pain for whom nonopioid analgesics had shown an insufficient analgesic effect. The patients were randomly assigned (1:1:1) to receive a single intravenous dose of fosphenytoin at 18 mg/kg (high dose), a single intravenous dose of fosphenytoin at 12 mg/kg (low dose), or placebo. The primary endpoint was the mean change per hour (slope) in the numerical rating scale score from the baseline score until 120 min after dosing. Seventeen patients were randomly assigned to the low-dose fosphenytoin group (n = 6, median age 62.5 years, range 39-75 years), high-dose fosphenytoin group (n = 5, median age 69.0 years, range 22-75 years), and placebo group (n = 5, median age 52.0 years, range 38-72 years). One patient was excluded because of investigational drug dilution failure. This study was discontinued because of the influences of coronavirus disease 2019. The slope was significantly lower in the high- and low-dose fosphenytoin groups than in the placebo group (P < 0.001 and P = 0.016, respectively). Responsiveness to intravenous fosphenytoin (≥2-point reduction in the numerical rating scale score from baseline to 120 min after dosing) was inferred at plasma total phenytoin concentrations of 10-15 μg/mL. Treatment-emergent adverse events caused no safety concerns in the clinical setting and intravenous fosphenytoin was well tolerated. Intravenous fosphenytoin appears to be an effective and promising alternative treatment for acute zoster-associated pain. Trial Registration: ClinicalTrials.gov NCT04139330.

Comparing the efficacy of intravenous morphine versus ibuprofen or the combination of ibuprofen and acetaminophen in patients with closed limb fractures: a randomized clinical trial

INTRODUCTION

This study aims to investigate the effectiveness of intravenous ibuprofen or intravenous ibuprofen plus acetaminophen compared to intravenous morphine in patients with closed extremity fractures.

METHODS

A triple-blinded randomized clinical trial was conducted at a tertiary trauma center in Iran. Adult patients between 15 and 60 years old with closed, isolated limb fractures and a pain intensity of at least 6/10 on the visual analog scale (VAS) were eligible. Patients with specific conditions or contraindications were not included. Participants were randomly assigned to receive intravenous ibuprofen, intravenous ibuprofen plus acetaminophen, or intravenous morphine. Pain scores were assessed using the visual analog scale at baseline and 5, 15, 30, and 60 min after drug administration. The primary outcome measure was the pain score reduction after one hour.

RESULTS

Out of 388 trauma patients screened, 158 were included in the analysis. There were no significant differences in age or sex distribution among the three groups. The pain scores decreased significantly in all groups after 5 min, with the morphine group showing the lowest pain score at 15 min. The maximum effect of ibuprofen was observed after 30 min, while the ibuprofen-acetaminophen combination maintained its effect after 60 min. One hour after injection, pain score reduction in the ibuprofen-acetaminophen group was significantly more than in the other two groups, and pain score reduction in the ibuprofen group was significantly more than in the morphine group.

CONCLUSION

The study findings suggest that ibuprofen and its combination with acetaminophen have similar or better analgesic effects compared to morphine in patients with closed extremity fractures. Although morphine initially provided the greatest pain relief, its effect diminished over time. In contrast, ibuprofen and the ibuprofen-acetaminophen combination maintained their analgesic effects for a longer duration. The combination therapy demonstrated the most sustained pain reduction. The study highlights the potential of non-opioid analgesics in fracture pain management and emphasizes the importance of initiation of these medications as first line analgesic for patients with fractures. These findings support the growing trend of exploring non-opioid analgesics in pain management.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05630222 (Tue, Nov 29, 2022). The manuscript adheres to CONSORT guidelines.

Implications and future direction of the effect of reducing acetaminophen dosage in prescription combination drugs on mitigating hepatotoxicity

Dear editor, Acetaminophen is the most widely used pain relief medication around the globe. It is used as an antipyretic and treat various medical ailments, including mild to moderate pain [1]. However, studies have shown that acetaminophen is associated with several adverse consequences, among which hepatotoxicity is the most pronounced [2]. However, despite its well know side-effects and risk of hepatotoxicity, acetaminophen is widely prescribed and its overdosing is a serious issue. Moreover, many combination of medications prescribed for pain relief do contain acetaminophen as its component. Often a single dose of such combinations contains two or more drugs of which many recipient remain ignorant that they are ingesting acetaminophen in the prescribed combination of drugs. This ignorance can lead to overdosing of acetaminophen and subsequent risk of hepatotoxicity [3]. On January 13, 2011, the U.S FDA addressed this issue by asking manufacturers to limit acetaminophen dosage from 750 mg/tablet to 325 mg/tablet in combination acetaminophen and opioid medications. The U.S FDA also asked all its manufacturers to place a box warning on all the combination medications that contain acetaminophen as its component, stating its association with liver injury [4]. A recent study published in JAMA, March 2023, further authenticated this ruling [5]. The study assessed the impact of U.S FDA’s decision to limit the amount of acetaminophen dose to 325 mg/tablet in prescription combination opioid drugs on the incidence of subsequent hospitalization and acute liver failure. It was found that predicted incidence of hospitalization, a day prior to FDA announcement was 12.2 cases/ 100000 hospitalizations whereas in 2019 it was reduced to 4.4 cases/ 100000 hospitalizations. Prior to the announcement the percentage of acute liver failure caused by acetaminophen and opioid toxicity rose by 07% per year and it fell by 16% annually after the announcement. Hence, it was concluded that U.S FDA’s decision of limiting acetaminophen dosage to 325 mg/tablet in combination drugs helped in reducing the incidents of acetaminophen related hepatotoxicity [5]. The above stated study showed satisfying statistics regarding the decline hepatotoxicity with lower doses of acetaminophen in prescription combination drugs. However, the matter is still not totally resolved because the U.S FDA’s decision of reducing acetaminophen dosage was limited to the prescription combination medications and excluded the acetaminophen drugs available over-the-counter. ---Continue

Synthesis, Pharmacological Evaluation, and Molecular Modeling of Lappaconitine-1,5-Benzodiazepine Hybrids

Diterpenoid alkaloids, originating from the amination of natural tetracyclic diterpenes, have long interested scientists due to their medicinal uses and infamous toxicity which has limited the clinical application of the native compound. Alkaloid lappaconitine extracted from various Aconitum and Delphinium species has displayed extensive bioactivities and active ongoing research to reduce its adverse effects. A convenient route to construct hybrid molecules containing diterpenoid alkaloid lappaconitine and 3H-1,5-benzodiazepine fragments was proposed. The key stage involved the formation of 5'-alkynone-lappaconitines in situ by acyl Sonogashira coupling of 5'-ethynyllappaconitine, followed by cyclocondensation with o-phenylenediamine. New hybrid compounds showed low toxicity and outstanding analgesic activity in experimental pain models, which depended on the nature of the substituent in the benzodiazepine nucleus. An analogous dependence was also shown for the antiarrhythmic activity in the epinephrine arrhythmia test in vivo. Studies on the isolated atrium have shown that the mechanism of action of the new compounds is included the blockade of beta-adrenergic receptors and potassium channels. Molecular docking analysis was conducted to determine the binding potential of target molecules with the voltage-gated sodium channel NaV1.5. All obtained results provide a basis for future rational modifications of lappaconitine, reducing side effects, while retaining its therapeutic effects.

Analgesic Action of Acetaminophen via Kv7 Channels

The mechanism of acetaminophen (APAP) analgesia is at least partially unknown. Previously, we showed that the APAP metabolite N-acetyl-p-benzoquinone imine (NAPQI) activated Kv7 channels in neurons in vitro, and this activation of Kv7 channels dampened neuronal firing. Here, the effect of the Kv7 channel blocker XE991 on APAP-induced analgesia was investigated in vivo. APAP had no effect on naive animals. Induction of inflammation with λ-carrageenan lowered mechanical and thermal thresholds. Systemic treatment with APAP reduced mechanical hyperalgesia, and co-application of XE991 reduced APAP's analgesic effect on mechanical pain. In a second experiment, the analgesic effect of systemic APAP was not antagonized by intrathecal XE991 application. Analysis of liver samples revealed APAP and glutathione-coupled APAP indicative of metabolization. However, there were no relevant levels of these metabolites in cerebrospinal fluid, suggesting no relevant APAP metabolite formation in the CNS. In summary, the results support an analgesic action of APAP by activating Kv7 channels at a peripheral site through formation of the metabolite NAPQI.

Metabolomic Evaluation of N-Acetyl-p-Benzoquinone Imine Protein Adduct Formation with Therapeutic Acetaminophen Administration: Sex-based Physiologic Differences

BACKGROUND

Acetaminophen (APAP)-associated transaminase elevation, induced by N-acetyl-p-benzoquinone imine (NAPQI) protein adduction, remains an area of research interest. Distinct from known genetic, physiologic, and dosage associations dictating severity of hepatic injury, no known factors predict an absence of protein adduct formation at therapeutic APAP dosing.

HYPOTHESIS

Sex-based physiology is predictive of APAP-induced protein adduct formation and differential metabolite expression at therapeutic doses.

METHODS

This retrospective study interrogated serum samples collected for a prior study investigating fluctuations of alanine aminotransferase (ALT) over time with 4G daily APAP dosing for ≥ 16 days in subjects from Denver, Colorado. Subjects were grouped by adduct formation (n = 184) vs no adducts (n = 20). Samples were run on ultra-high-performance liquid chromatography mass spectrometry from study days 0, 7, 16, and 31. Significant metabolite expressions were identified using t-tests with false discovery rate correction (FDR), partial least squares discriminant, and ANOVA simultaneous comparison analyses. Demographic and clinical data were explored using t-tests with FDR (age, weight, BMI, ALT) and Chi-square (sex, ethnicity, race) analyses.

RESULTS

In pre-treatment samples, relative quantitation caprylic acid was expressed ninefold higher and 6-carboxyhexanoate was expressed threefold lower in subjects who did not develop adducts. Lactate had greater expression in the no adducts group (p = 0.001). Using absolute quantitation, glutathione was expressed 2.6-fold greater among no adduct subjects. Odds of males developing NAPQI protein adducts at therapeutic APAP dosing were 5.91 times lower than females (95% CI = 2.3-14.9; p = 0.0001).

CONCLUSION

Multiple metabolites were differentially expressed based on adduct group and sex. Metabolites were identified unique to adduct development independent of sex. At therapeutic APAP dosing, males were less likely to develop APAP protein adducts. Further research into lipid biosynthesis and metabolism may provide further insight into physiology associated with adduct production.

Structure-based discovery of nonopioid analgesics acting through the α2A-adrenergic receptor

Because nonopioid analgesics are much sought after, we computationally docked more than 301 million virtual molecules against a validated pain target, the α2A-adrenergic receptor (α2AAR), seeking new α2AAR agonists chemotypes that lack the sedation conferred by known α2AAR drugs, such as dexmedetomidine. We identified 17 ligands with potencies as low as 12 nanomolar, many with partial agonism and preferential Gi and Go signaling. Experimental structures of α2AAR complexed with two of these agonists confirmed the docking predictions and templated further optimization. Several compounds, including the initial docking hit '9087 [mean effective concentration (EC50) of 52 nanomolar] and two analogs, '7075 and PS75 (EC50 4.1 and 4.8 nanomolar), exerted on-target analgesic activity in multiple in vivo pain models without sedation. These newly discovered agonists are interesting as therapeutic leads that lack the liabilities of opioids and the sedation of dexmedetomidine.

Restoration Algorithm-Based Ultrasound Image in Evaluating the Effect of Dexmedetomidine on Patients with Neurological Disorder Anesthetized by Sevoflurane

The study focused on the application value of ultrasound images processed by restoration algorithm in evaluating the effect of dexmedetomidine in preventing neurological disorder in patients undergoing sevoflurane anesthesia. 90 patients undergoing tonsillectomy anesthesia were randomly divided into normal saline group, propofol group, and dexmedetomidine group. The ultrasound images were processed by restoration algorithm, and during the postoperative recovery period, ultrasound images were used to evaluate. The results showed that the original ultrasonic image was fuzzy and contained interference noise, and that the image optimized by restoration algorithm was clear, without excess noise, and the image quality was significantly improved. In the dexmedetomidine group, the extubation time was 10.6 ± 2.3 minutes, the recovery time was 8.4 ± 2.2 minutes, the average pain score during the recovery period was 2.6 ± 0.7, and the average agitation score was 7.2 ± 2.4. Of 30 patients, there were 13 cases with vertigo and 1 case with nausea and vomiting. The vascular ultrasound imaging showed that, in the dexmedetomidine group, the peak systolic velocities (PSV) of the bilateral vertebral arteries during the recovery period were 67.7 ± 14.3 and 67.9 ± 15.2 cm/s, respectively; the end-diastolic velocities (EDV) of the bilateral vertebral arteries were 27.8 ± 6.7 and 24.69 ± 5.9 cm/s, respectively; the PSV in bilateral internal carotid artery systolic peak velocities were 67.2 ± 13.9 and 67.8 ± 12.7 cm/s, respectively; the EDV in bilateral internal carotid arteries were 27.7 ± 5.3 and 26.9 ± 4.9 cm/s, respectively; bilateral vertebral artery resistance indexes (RIs) were 0.6 ± 0.02 and 0.71 ± 0.08, respectively; the bilateral internal carotid artery RIs were 0.57 ± 0.04 and 0.58 ± 0.06, respectively, all better than the normal saline group (12.1 ± 2.5 minutes, 10.1 ± 2.3 minutes, 3.9 ± 0.6, 10.6 ± 3.7, 15 cases, 11 cases, 81.5 ± 13.6, 80.7 ± 11.6 cm/s, 29.3 ± 6.8, 28.9 ± 6.7 cm/s, 74.3 ± 10.2, 73.9 ± 12.5 cm/s, 29.1 ± 4.3, 29 ± 4.5 cm/s, 0.84 ± 0.06, 0.83 ± 0.05, 0.8 ± 0.04, and 0.81 ± 0.05) and the propofol group (11.4 ± 2.1 minutes, 9.0 ± 2.1 minutes, 3.4 ± 0.8, 8.5 ± 2.3, 12 cases, 9 cases, 72.5 ± 12.9, 73.4 ± 11.8 cm/s, 28.6 ± 5.4, 26.5 ± 5.1 cm/s, 72.1 ± 11.4, 73.5 ± 10.6 cm/s, 28.8 ± 5.6, 27.3 ± 4.7 cm/s, 0.78 ± 0.07, 0.82 ± 0.06, 0.76 ± 0.03, and 0.78 ± 0.05), and the differences were statistically significant (P < 0.05). In conclusion, ultrasound images processed by restoration algorithm have high image quality and high resolution. The dexmedetomidine can prevent neurological disorder in patients with sevoflurane anesthesia and is suggested in postoperative rehabilitation.

Dexmedetomidine-soaked nasal packing can reduce pain and improve sleep quality after nasal endoscopic surgery: a double-blind, randomized, controlled clinical trial

STUDY OBJECTIVE

Bilateral endoscopic nasal surgery is usually associated with pain and sleep disturbance. The aim of this study was to evaluate the effects of dexmedetomidine-soaked nasal packing on analgesia and improvement of sleep quality in patients undergoing this surgery.

METHOD

Eighty patients were enrolled and randomly allocated into 4 groups. At the end of surgery, dexmedetomidine-soaked nasal packings were applied to three groups with a dosage of 1 μg kg^-1 (D1), 2μg kg^-1 (D2), 4 μg kg^-1 (D4) and normal saline-soaked nasal packing (NS) was applied to a fourth group. The primary outcome was postoperative pain scores using a visual analog scale (VAS) recorded at six time points: before the surgery (T1); 2 h (T2), 8 h (T3), 24 h (T4), 48 h (T5) after surgery; and at the moment of nasal packing removal (T6). Secondary outcomes were postoperative sleep status evaluated by the Pittsburgh sleep quality index (PSQI) and subjective sleep quality value (SSQV). Factors affecting sleep, hemodynamic changes, and adverse events were also recorded.

RESULTS

Compared with the NS group, dexmedetomidine-soaked nasal packing significantly relieved postoperative pain and improved sleep quality. The effect was similar between D2 and D4, which was greater than in D1. However, D2 was associated with fewer adverse events.

CONCLUSIONS

Dexmedetomidine-soaked nasal packing not only offers effective analgesia but also improves postoperative sleep quality in patients undergoing bilateral endoscopic nasal surgery. Taking effect and adverse events into consideration, a dosage of 2μg kg^-1 may be optimal.

TRIAL REGISTRATION

www.chictr.org.cn/index.aspx (ChiCTR1900025692) Retrospectively registered 5 September 2019.

No antinociceptive synergy between morphine and delta-9-tetrahydrocannabinol in male and female rats with persistent inflammatory pain

Studies have demonstrated antinociceptive synergy between morphine and delta-9-tetrahydrocannabinol (THC) in animals, but whether such synergy occurs against all types of pain and in humans is unclear. Because a majority of chronic pain patients are women, and sex differences in morphine and THC potencies have been observed in rodents, the present study examined sex-specific effects of morphine and THC given alone and in combination, in rats with persistent inflammatory pain. On day 1, baseline mechanical and thermal response thresholds, hindpaw weight-bearing, locomotor activity, and hindpaw thickness were determined. Inflammation was then induced via hindpaw injection of complete Freund's adjuvant (CFA). Three days later, morphine (s.c.), THC (i.p) or a morphine-THC combination (1:1, 3:1 and 1:3 dose ratios) was administered, and behavioral testing was conducted at 30-240 min postinjection. Morphine alone was antiallodynic and antihyperalgesic, with no sex differences, but at some doses increased weight-bearing on the CFA-treated paw more in males than females. THC alone reduced mechanical allodynia with similar potency in both sexes, but reduced thermal hyperalgesia and locomotor activity with greater potency in females than males. All morphine-THC combinations reduced allodynia and hyperalgesia, but isobolographic analysis of mechanical allodynia data showed no significant morphine-THC synergy in either sex. Additionally, whereas morphine alone was antinociceptive at doses that did not suppress locomotion, morphine-THC combinations suppressed locomotion and did not increase weight-bearing on the inflamed paw. These results suggest that THC is unlikely to be a beneficial adjuvant when given in combination with morphine for reducing established inflammatory pain.

Nalbuphine and dexmedetomidine as adjuvants to ropivacaine in ultrasound-guided erector spinae plane block for video-assisted thoracoscopic lobectomy surgery: A randomized, double-blind, placebo-controlled trial

BACKGROUND

Adjuvants to local anesthetics, such as nalbuphine and dexmedetomidine, can be used to improve the quality and duration of peripheral nerve block effects. Dexmedetomidine has been successfully used as an adjuvant of erector spinae plane block (ESPB) with ropivacaine in video-assisted thoracoscopic lobectomy surgeries (VATLS). This study aimed to compare the effects of nalbuphine and dexmedetomidine used as adjuvants to ropivacaine for ESPB in VATLS.

METHODS

A total of 102 patients undergoing VATLS with ESPB were enrolled and randomized into 3 groups, each of which received a different adjuvant to ropivacaine. The visual analogue scale score, onset and duration of sensory block, use of patient-controlled analgesia (PCA), rate of rescue analgesia, duration of postoperative hospitalization, incidence of postoperative nausea and vomiting, and chronic pain were measured and observed.

RESULTS

The visual analogue scale score, total PCA use, rate of rescue analgesia, and postoperative chronic pain in the ropivacaine with dexmedetomidine (RD), and ropivacaine with nalbuphine (RN) groups were lower than those in the ropivacaine (RC) group (P < .05). The duration of sensory block was longer and the first use of PCA occurred later in the RD and RN groups than they did in the RC group (P < .05).

CONCLUSIONS

As an adjuvant to ropivacaine in ESPB, nalbuphine and dexmedetomidine are comparable in terms of the associated analgesia, sensory block duration, need for rescue analgesia, and incidence of chronic pain in patients after VATLS.

Pharmacological hypotheses: Is acetaminophen selective in its cyclooxygenase inhibition?

The precise mechanistic action of acetaminophen (ACT; paracetamol) remains debated. ACT's analgesic and antipyretic actions are attributed to cyclooxygenase (COX) inhibition preventing prostaglandin (PG) synthesis. Two COX isoforms (COX1/2) share 60% sequence structure, yet their functions vary. COX variants have been sequenced among various mammalian species including humans. A COX1 splice variant (often termed COX3) is purported by some as the elusive target of ACT's mechanism of action. Yet a physiologically functional COX3 isoform has not been sequenced in humans, refuting these claims. ACT may selectively inhibit COX2, with evidence of a 4.4-fold greater COX2 inhibition than COX1. However, this is markedly lower than other available selective COX2 inhibitors (up to 433-fold) and tempered by proof of potent COX1 inhibition within intact cells when peroxide tone is low. COX isoform inhibition by ACT may depend on subtle in vivo physiological variations specific to ACT. In vivo ACT efficacy is reliant on intact cells and low peroxide tone while the arachidonic acid concentration state can dictate the COX isoform preferred for PG synthesis. ACT is an effective antipyretic (COX2 preference for PG synthesis) and can reduce afebrile core temperature (likely COX1 preference for PG synthesis). Thus, we suggest with specificity to human in vivo physiology that ACT: (i) does not act on a third COX isoform; (ii) is not selective in its COX inhibition; and (iii) inhibition of COX isoforms are determined by subtle and nuanced physiological variations. Robust research designs are required in humans to objectively confirm these hypotheses.

Acetaminophen Exerts an Analgesic Effect on Muscular Hyperalgesia in Repeated Cold-Stressed Rats through the Enhancement of the Descending Pain Inhibitory System Involving Spinal 5-HT3 and Noradrenergic α2 Receptors

Musculoskeletal and psychological complaints have increased with the widespread use of visual display terminals, and musculoskeletal pain is known to be closely related to stress. One method of experimentally inducing persistent muscle pain is repeated cold stress (RCS), and animals exposed to such stress exhibit a dysfunction in the descending pain inhibitory system. Acetaminophen (N-acetyl-p-aminophenol; APAP) is widely used to relieve several types of pain, including musculoskeletal pain, and is available as an OTC drug. However, the mechanism underlying its analgesic action has not yet been fully elucidated. In this study, we compared the analgesic effect of APAP on RCS-induced muscular hyperalgesia with those of other analgesics to identify its mechanism of action. The daily oral administration of APAP significantly suppressed the decrease in the mechanical withdrawal threshold caused by RCS, similar to the results for neurotropin but not for the cyclooxygenase inhibitor ibuprofen (IBP). Moreover, the intrathecal administration of antagonists of the 5-hydroxytryptamine (5-HT)3 receptor or α2-adrenoceptor significantly abolished the analgesic effect of APAP but not of IBP. These results suggest that the analgesic effect of APAP on RCS-induced muscular pain might be exerted due to the activation of the descending pathways involving the spinal 5-HT3 receptor or α2-adrenoceptor.

Pharmacodynamic and pharmacokinetic profiles of a neurotensin receptor type 2 (NTS2) analgesic macrocyclic analog

The current opioid crisis highlights the urgent need to develop safe and effective pain medications. Thus, neurotensin (NT) compounds represent a promising approach, as the antinociceptive effects of NT are mediated by activation of the two G protein-coupled receptor subtypes (i.e., NTS1 and NTS2) and produce potent opioid-independent analgesia. Here, we describe the synthesis and pharmacodynamic and pharmacokinetic properties of the first constrained NTS2 macrocyclic NT(8-13) analog. The Tyr¹¹ residue of NT(8-13) was replaced with a Trp residue to achieve NTS2 selectivity, and a rationally designed side-chain to side-chain macrocyclization reaction was applied between Lys⁸ and Trp¹¹ to constrain the peptide in an active binding conformation and limit its recognition by proteolytic enzymes. The resulting macrocyclic peptide, CR-01-64, exhibited high-affinity for NTS2 (K_i 7.0 nM), with a more than 125-fold selectivity over NTS1, as well as an improved plasma stability profile (t_1/2 > 24 h) compared with NT (t_1/2 ~ 2 min). Following intrathecal administration, CR-01-64 exerted dose-dependent and long-lasting analgesic effects in acute (ED₅₀ = 4.6 µg/kg) and tonic (ED₅₀ = 7.1 µg/kg) pain models as well as strong mechanical anti-allodynic effects in the CFA-induced chronic inflammatory pain model. Of particular importance, this constrained NTS2 analog exerted potent nonopioid antinociceptive effects and potentiated opioid-induced analgesia when combined with morphine. At high doses, CR-01-64 did not cause hypothermia or ileum relaxation, although it did induce mild and short-term hypotension, all of which are physiological effects associated with NTS1 activation. Overall, these results demonstrate the strong therapeutic potential of NTS2-selective analogs for the management of pain.

Efficacy and safety of ibuprofen in children with musculoskeletal injuries: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

To evaluate the analgesic efficacy and safety of ibuprofen in children with musculoskeletal injuries.

METHODS

PubMed, EMBASE, Web of science, and the Cochrane Central register of Controlled Trials (CENTRAL) were systematically searched to identify eligible randomized controlled trials (RCTs) that compared ibuprofen with other analgesics for pain relief in children with musculoskeletal injuries. Primary outcomes included change of visual analog scale (VAS) scores from baseline to post-medication, the proportion of patients achieving adequate analgesia, and the proportion of patients requiring additional analgesia. Secondary outcome was the incidence of adverse effects. Data analysis was performed using RevMan 5.3 software.

RESULTS

Five RCTs involving 1034 patients were included in this meta-analysis. Compared to the control group, change of VAS scores was greater in ibuprofen group at 60 min (standardized mean difference [SMD] = 0.28; 95% confidence intervals [CI], 0 to 0.57; P = .05), 90 min (SMD = 0.38; 95% CI, 0.17 to 0.59; P = .0005), and 120 min (SMD = 0.4; 95% CI, 0.23 to 0.57; P < .00001) after treatment. No difference was found in the change of VAS scores at 30 min (SMD = 0.07; 95% CI, -0.08 to 0.22; P = .36) after treatment. The proportion of patients who received adequate analgesia was higher in the ibuprofen group (risk ratios [RR] = 1.36; 95% CI, 1.20 to 1.56; P < .00001). The proportion of patients that required additional analgesia was lower in the ibuprofen group (RR = 0.7; 95% CI, 0.53 to 0.92; P = .01). The incidence of total adverse effects was lower in the ibuprofen group (RR = 0.59; 95% CI, 0.45 to 0.79; P = .0002).

CONCLUSIONS

Ibuprofen provides a better pain relief with a lower incidence of adverse effects in children with musculoskeletal injuries as compared to other analgesics.

PROSPERO REGISTRATION NUMBER

CRD42021231975.

Pain Relieving and Neuroprotective Effects of Non-opioid Compound, DDD-028, in the Rat Model of Paclitaxel-Induced Neuropathy

Chemotherapy-induced neuropathy (CIN) is a major dose-limiting side effect of anticancer therapy that can compel therapy discontinuation. Inadequate analgesic efficacy of current pharmacological approaches requires the identification of innovative therapeutics and, hence, the purpose of this study is to conduct a preclinical evaluation of the efficacy of DDD-028, a versatile pentacyclic pyridoindole derivative, against paclitaxel-induced neuropathic pain. In two separate experiments, DDD-028 was administered per os acutely (1-25 mg kg-1) or repeatedly (10 mg kg-1) in paclitaxel-treated rats. The response to mechanical noxious stimulus (paw pressure) as well as to non-noxious mechanical (von Frey) and thermal (cold plate) stimuli was investigated. Acute administration of DDD-028 induced a dose-dependent anti-neuropathic pain effect in all tests performed. Further, repeated daily treatment for 18 consecutive days (starting the first day of paclitaxel administration) significantly reduced the development of pain over time without the development of tolerance to the anti-hyperalgesic effect. Ex vivo analysis showed that DDD-028 was able to reduce oxidative damage of dorsal root ganglia as evidenced by the increase in the level of carbonylated proteins and the decrease in catalase activity. In the lumbar spinal cord, periaqueductal gray matter, thalamus, and somatosensory cortex 1, DDD-28 significantly prevented the activation of microglia and astrocytes. The pharmacodynamic study revealed that the pain-relieving effects of DDD-028 were fully blocked by both the non-selective nicotinic receptor (nAChR) antagonist mecamylamine and by the selective α7 nAChR antagonist methyllycaconitine. In conclusion, DDD-028 was active in reducing paclitaxel-induced neuropathic pain after single or repeated administrations without tolerance development and displaying a double symptomatic and neuroprotective profile. DDD-028 could represent a valuable candidate for the treatment of CIN.

Ethenzamide Exerts Protective Effects against Ibuprofen-Induced Gastric Mucosal Damage in Rats by Suppressing Gastric Contraction

Nonsteroidal anti-inflammatory drugs (NSAIDs) are known to cause gastric mucosal damage, in which gastric hypermotility has been reported to play a primary role. The antipyretic analgesic drug ethenzamide (ETZ) is widely used in combination with other NSAIDs and, in a recent study, was found to possess 5-hydroxytriptamine (5HT)2B receptor antagonistic activity. Therefore, the inhibition of gastric contraction via 5HT2B receptor blockade by ETZ might contribute to ETZ's protective effect against NSAIDs-induced gastric mucosal damage. In the present study, we examined the effects of ETZ on gastric contraction and ibuprofen (IBP)-induced gastric mucosal damage in rats. We found that ETZ suppressed both 5HT- and α-methyl-5HT (5HT2 receptor agonist)-induced contractions of rat-isolated gastric fundus in a concentration-dependent manner. This suppressive effect of ETZ was not seen for either high-KCl- or acetylcholine-induced contractions. Furthermore, ETZ was confirmed to decrease ibuprofen-induced gastric mucosal damage in a dose-dependent manner in rats. Similarly, clonidine is known to reduce gastric motility, and methysergide (a 5HT2 receptor antagonist) is known to inhibit 5HT-induced contractions of the gastric fundus, which also decreases IBP-induced gastric mucosal damage, respectively. Although further research on other possible sites or mechanisms of action would be needed, these results suggest that ETZ exerts a protective effect against IBP-induced gastric mucosal damage and that suppressing the gastric contraction may play an important role in the gastroprotective effect of ETZ.

Effect of the morphine/heroin vaccine on opioid and non-opioid drug-induced antinociception in mice

Pain is a common symptom in patients with opioid use disorder (OUD), which increases synthetic and illicit synthetic opioid abuse and even fatalities due to opioid overdose. Many FDA-approved drugs are available for the treatment of OUD, however, the use of these medications is limited, mainly due to the development of various side effects. Active vaccination is a new therapeutic approach but the resulting antibodies may compromise the use and efficiency of opioid and non-opioid drugs. In this study, we evaluated whether the antibodies produced by the morphine/heroin vaccine (M-TT) would alter the antinociceptive effects of opioid and non-opioid drugs. Female Balb-c mice were immunized with the M-TT vaccine. A solid-phase antibody-capture ELISA was used for monitoring antibody titer responses after each booster dose in vaccinated animals, followed by tail-flick testing. This study found that the M-TT vaccine did not affect the antinociception induced by different doses of morphine or the ability of non-opioid and synthetic opioid drugs to decrease thermal pain. Moreover, the combination of vaccination and naloxone increased the time-course of morphine antagonism relative to either vaccination or naloxone alone. These results suggest that the antibody titers generated by the M-TT vaccine 1) are capable of reducing morphine-induced antinociception and 2) are selective enough not to alter antinociception induced by non-opioid or synthetic drugs. These characteristics support its potential as a treatment agent for patients with symptoms of pain comorbid to OUD.

Role of orexin receptors within the dentate gyrus in antinociception induced by chemical stimulation of the lateral hypothalamus in an animal model of inflammatory pain

Pain is a complex experience consisting of sensory, affective-motivational, and cognitive dimensions. Hence, identifying the multiple neural pathways subserving these functional aspects is a valuable task. The role of dentate gyrus (DG) as a relay station of neocortical afferents in the hippocampal formation (HF) in persistent pain is still controversial. The lateral hypothalamus (LH)-HF neural circuits are involved in numerous situations such as anxiety-like behavior, reward processing, feeding, orofacial as well as acute pain. Nonetheless, to our knowledge, the involvement of the LH-DG neural circuit in persistent pain has already remained unexplored. Adult male Wistar rats weighing 220-250 g were undergone stereotaxic surgery for unilateral implantation of two separate cannulae into the LH and DG. Intra-DG administration of the orexin-1 (OX1) and orexin-2 (OX2) receptor antagonists, SB334867 and TCS OX2 29, respectively, was performed 5 min before intra-LH microinjection of carbachol. Animals were then undergone the formalin test using 50 μl formalin injection (2.5%) into the plantar surface of the hind paw. Microinjection of SB334867 or TCS OX2 29 into the DG region attenuated the antinociceptive effect produced by carbachol microinjection into the LH. The preventive effect of SB334867 and TCS OX2 29 on intra-LH carbachol-induced antinociception was approximately equal in both early and late phases of formalin nociception. The results suggest a neural pathway from the LH to the DG, which contributes to the modulation of formalin-induced inflammatory pain through the recruitment of OX1 and OX2 receptors within the DG.

The Influence of Paracetamol on the Penetration of Sorafenib and Sorafenib N-Oxide Through the Blood-Brain Barrier in Rats

Background and Objective

Sorafenib is an oral, multikinase inhibitor with established single-agent activity in several tumor types. Sorafenib was moderately transported by P-glycoprotein (P-gp) and more efficiently by breast cancer resistance protein. The constitutive androstane receptor (CAR) is a ligand-activated transcription factor involved in P-gp regulation in the brain microvasculature. Paracetamol is a CAR activator. The purpose of this study was to investigate the effect of paracetamol on the brain uptake of sorafenib and sorafenib N-oxide.

Methods

The rats were assigned to two groups—rats receiving oral paracetamol 100 mg/kg and sorafenib 100 mg/kg (n = 42, I_SR+PA) and rats receiving oral vehicle and sorafenib 100 mg/kg (n = 42, II_SR). The sorafenib and sorafenib N-oxide concentrations in blood plasma and brain tissue were determined by a high-performance liquid chromatography method with ultraviolet detection. Brain-to-plasma partition coefficient (K_p) was calculated as a ratio of the area under the curve from zero to 24 h (AUC) in the brain and plasma. A drug targeting index (DTI) was estimated as the group I_SR+PAK_p to group II_SRK_p ratio.

Results

Pharmacokinetic analysis revealed increased brain exposure to sorafenib and sorafenib N-oxide after co-administration of paracetamol. The brain maximum concentration (C_max) and the AUC of the parent drug in the I_SR+PA group compared with the II_SR group were greater by 49.5 and 77.8%, respectively, and the same parameters for the metabolite were higher by 51.4 and 50.9%. However, the K_p values of sorafenib and sorafenib N-oxide did not differ significantly between the two animal groups and the DTI values were close to 1.

Conclusion

Paracetamol increases exposure to sorafenib and sorafenib N-oxide in the brain, likely due to increased exposure in plasma.

Zingiber officinale Roscoe rhizome extract alleviates neuropathic pain by inhibiting neuroinflammation in mice

BACKGROUND

Current therapies for neuropathic pain are generally symptomatic and possess several side effects, limiting their prolonged usage.

HYPOTHESIS/PURPOSE

Thus, it is urgent to develop novel and safe candidates for the management of this chronical condition. For this purpose, we investigated the analgesic effect of a standardized extract from Zingiber officinale Roscoe rhizomes (ZOE) obtained by CO2 supercritical extraction, in a mice model of peripheral neuropathy. We also explored the mechanism of action of ZOE and its main constituents using an in vitro model of neuroinflammation.

METHODS

Peripheral mono-neuropathy was induced in mice, by spared nerve injury (SNI). The analgesic effect of ZOE after oral administration was assessed by measuring mechanical and thermal allodynia in SNI mice. The mechanism of action of ZOE and its main constituents were investigated using spinal cords samples and in an in vitro model of neuroinflammation by ELISA, western blotting and immunofluorescence techniques.

RESULTS

Oral administration of ZOE 200 mg kg-1 ameliorated mechanical and thermal allodynia in SNI mice, with a rapid and a long-lasting effect. ZOE did not alter locomotor activity. In BV2 cells and spinal cord samples, ZOE, 6-gingerol and 6-shogaol reduced pERK levels, whereas ZOE and terpene fraction reduced HDAC1 protein levels, inhibited NF-κB signalling activation and decreased IL-1β, TNF-α and IL-6 release. ZOE and each tested constituent had a positive effect on inflammation-impaired SH-SY5Y cell viability.

CONCLUSIONS

The oral administration of ZOE attenuated SNI-induced neuropathic pain symptoms by reducing spinal neuroinflammation, suggesting ZOE as a novel and interesting candidate for the management of neuropathic pain.

Effects of nitrous oxide on glycinergic transmission in rat spinal neurons

We investigated the effects of nitrous oxide (N₂O) on glycinergic inhibitory whole-cell and synaptic responses using a "synapse bouton preparation," dissociated mechanically from rat spinal sacral dorsal commissural nucleus (SDCN) neurons. This technique can evaluate pure single- or multi-synaptic responses from native functional nerve endings and enable us to accurately quantify how N₂O influences pre- and postsynaptic transmission. We found that 70 % N₂O enhanced exogenous glycine-induced whole-cell currents (I_Gly) at glycine concentrations lower than 3 × 10^-5 M, but did not affect I_Gly at glycine concentrations higher than 10^-4 M. N₂O did not affect the amplitude and 1/e decay-time of both spontaneous and miniature glycinergic inhibitory postsynaptic currents recorded in the absence and presence of tetrodotoxin (sIPSCs and mIPSCs, respectively). The decrease in frequency induced by N₂O was observed in sIPSCs but not in mIPSCs, which was recorded in the presence of both tetrodotoxin and Cd²⁺, which block voltage-gated Na⁺ and Ca²⁺ channels, respectively. N₂O also decreased the amplitude and increased the failure rate and paired-pulse ratio of action potential-evoked glycinergic inhibitory postsynaptic currents. N₂O slightly decreased the Ba²⁺ currents mediated by voltage-gated Ca²⁺ channels in SDCN neurons. We found that N₂O suppresses glycinergic responses at synaptic levels with presynaptic effect having much more predominant role. The difference between glycinergic whole-cell and synaptic responses suggests that extrasynaptic responses seriously modulate whole-cell currents. Our results strongly suggest that these responses may thus in part explain analgesic effects of N₂O via marked glutamatergic inhibition by glycinergic responses in the spinal cord.

Hepatoprotective and antioxidant activity of Dicliptera bupleuroides Nees. extracts on paracetamol induced hepatotoxicity in rats

Aim of this study to evaluate the safety profile, hepatoprotective and in-vivo antioxidant activities of Dicliptera bupleuroides Nees. Toxicity studies were conducted in human RBCs and DNA by using standard procedures. Acute hepatoprotective investigation was carried out in albino rats by treated with all six fractions of D. bupleuroides 350 mg/kg/day. ALT, AST, ALP and total bilirubin (TB) were performed. The n-hexane fraction (200 mg/kg/day) exhibited appropriate hepatoprotective activity hence subjected to chronic study (14 days). Paracetamol induced the hepatotoxicity (350mg/kg) and silymarin (50 mg/kg) was standard drug. Liver function tests, liver peroxidation tests and histopathological examination were performed at the end. Hexane fraction showed significant decrease in the level of ALT (88.1±7.8), AST (93.8±7.6), ALP (136.3±8.4) and TB (0.6±0.03) as compared to the standard drug (p>0.05). Rats treated with ethyl acetate fraction showed decrease in MDA (42.8±0.7) while GSH was found to be increased (107.7±1.8) against the toxic group (51.3±2.9), (73.6±4.0) respectively. All the drug extracts decreased the oxidative stress and protect the DNA from free hydroxyl radicals. DNA damage protection activity of these fractions is due to phytochemicals present in these fractions. These results indicate that the plant fractions possess significant hepatoprotective and antioxidant activities with no toxic effects.

Effects of dexmedetomidine on cognitive function in elderly patients after laparoscopic cholecystectomy: A protocol for systematic review and meta-analysis

BACKGROUND

Although many studies have reported the effects of dexmedetomidine on cognitive function (CF) in elderly patients after laparoscopic cholecystectomy (LCT), to this date, its effects are still not well understood. The aim of this study is to produce a qualitative synthesis of assessing the effects of dexmedetomidine on CF in elderly patients after LCT.

METHODS

We will conduct a comprehensive search in Cochrane Library, MEDLINE, EMBASE, CINAHL, PsycINFO, Scopus, VIP Database, WANGFANG Database, Chinese Biomedical Literature Database, and China National Knowledge Infrastructure from the commencement to March 31, 2020 without restrictions of language and publication status. In addition, we will also search grey literature, including conference abstracts, dissertations, reference lists of included studies and relevant reviews. All potential studies will be identified independently by 2 authors to determine their inclusion against previously defined eligibility criteria. The quality of selected papers will be assessed using Cochrane risk of bias tool. All statistical analysis will be performed using RevMan 5.3 software.

RESULTS

This study will provide a synthesis of the current available data on assessing the effects of dexmedetomidine on CF in elderly patients after LCT.

CONCLUSIONS

Its findings will provide qualitative evidence to better understand the effects of dexmedetomidine on CF in elderly patients after LCT.INPLASY Registration Number: INPLASY202040030.

Cell-permeable succinate prodrugs rescue mitochondrial respiration in cellular models of acute acetaminophen overdose

Acetaminophen is one of the most common over-the-counter pain medications used worldwide and is considered safe at therapeutic dose. However, intentional and unintentional overdose accounts for up to 70% of acute liver failure cases in the western world. Extensive research has demonstrated that the induction of oxidative stress and mitochondrial dysfunction are central to the development of acetaminophen-induced liver injury. Despite the insight gained on the mechanism of acetaminophen toxicity, there still is only one clinically approved pharmacological treatment option, N-acetylcysteine. N-acetylcysteine increases the cell’s antioxidant defense and protects liver cells from further acetaminophen-induced oxidative damage. Because it primarily protects healthy liver cells rather than rescuing the already injured cells alternative treatment strategies that target the latter cell population are warranted. In this study, we investigated mitochondria as therapeutic target for the development of novel treatment strategies for acetaminophen-induced liver injury. Characterization of the mitochondrial toxicity due to acute acetaminophen overdose in vitro in human cells using detailed respirometric analysis revealed that complex I-linked (NADH-dependent) but not complex II-linked (succinate-dependent) mitochondrial respiration is inhibited by acetaminophen. Treatment with a novel cell-permeable succinate prodrug rescues acetaminophen-induced impaired mitochondrial respiration. This suggests cell-permeable succinate prodrugs as a potential alternative treatment strategy to counteract acetaminophen-induced liver injury.

Loganin prevents chronic constriction injury-provoked neuropathic pain by reducing TNF-α/IL-1β-mediated NF-κB activation and Schwann cell demyelination

BACKGROUND

Peripheral nerve injury can produce chronic and ultimately neuropathic pain. The chronic constriction injury (CCI) model has provided a deeper understanding of nociception and chronic pain. Loganin is a well-known herbal medicine with glucose-lowering action and neuroprotective activity.

PURPOSE

This study investigated the molecular mechanisms by which loganin reduced CCI-induced neuropathic pain.

METHODS

Sprague-Dawley rats were randomly divided into four groups: sham, sham+loganin, CCI and CCI+loganin. Loganin (1 or 5 mg/kg/day) was injected intraperitoneally once daily for 14 days, starting the day after CCI. For behavioral testing, mechanical and thermal responses were assessed before surgery and on d1, d3, d7 and d14 after surgery. Sciatic nerves (SNs) were collected to measure proinflammatory cytokines. Proximal and distal SNs were collected separately for Western blotting and immunofluorescence studies.

RESULTS

Thermal hyperalgesia and mechanical allodynia were reduced in the loganin-treated group as compared to the CCI group. Loganin (5 mg/kg/day) prevented CCI from inducing proinflammatory cytokines (TNF-α, IL-1β), inflammatory proteins (TNF-α, IL-1β, pNFκB, pIκB/IκB, iNOS) and receptor (TNFR1, IL-1R), adaptor protein (TRAF2) of TNF-α, and Schwann cell demyelination and axonal damage. Loganin also blocked IκB phosphorylation (p-IκB). Double immunofluorescent staining further demonstrated that pNFκB/pIκB protein was reduced by loganin in Schwann cells on d7 after CCI. In the distal stumps of injured SN, Schwann cell demyelination was correlated with pain behaviors in CCI rats.

CONCLUSION

Our findings indicate that loganin improves CCI-induced neuroinflammation and pain behavior by downregulating TNF-α/IL-1β-dependent NF-κB activation.

Effects of a single paracetamol injection on the sevoflurane minimum alveolar concentration in dogs

This study aimed to determine the effect of a single injection of paracetamol on the sevoflurane minimum alveolar concentration (MAC) response to noxious mechanical stimulation. Seven healthy adult beagles were enrolled in a prospective, randomized, blinded, crossover experimental study. Anesthesia was induced with propofol [11.6 ± 2.4 mg/kg body weight (BW)] and maintained with sevoflurane. The MAC was determined before (MAC-1) and after (MAC-2) treatment with 15 mg/kg BW of intravenous (IV) paracetamol or saline over 15 minutes. Samples for plasma paracetamol determination were collected immediately after IV treatment administration and following MAC-2 determination (123 ± 27 minutes after starting paracetamol administration). The MAC-1 was similar between treatments (1.7% ± 0.4%). There were no differences between control and paracetamol groups at MAC-2 (2.0% ± 0.4% and 1.7% ± 0.5%, respectively; P = 0.285). Paracetamol plasma concentrations after paracetamol administration were 34.5 ± 9.9 μg/mL, decreasing at the end of the procedure (8.5 ± 4.2 μg/mL). In conclusion, 15 mg/kg BW of IV paracetamol did not significantly reduce sevoflurane MAC in healthy dogs.

Cellular cytokine receptor signaling and ATM pathway intersections affect hepatic DNA repair

Pathways involving ataxia telangiectasia mutated (ATM) gene and its downstream partners and effectors are critical for the DNA damage response. Cell survival, proliferation and tissue homeostasis are dependent upon preservation of DNA integrity but additional intracellular mechanisms contribute in these processes. As receptor-mediated signaling with beneficial intersections in ATM pathways could have therapeutic significance, we interrogated such intersections with assays using HuH-7 cells (hepatocytes). These cells were subjected to acetaminophen toxicity, which is a leading cause of hepatic injury and acute liver failure in people. The ATM pathway was examined in HuH-7-ATM-Prom-tdT cells containing fluorescent td-Tomato transgene reporter for ATM promoter activity. Titrated doses of specific growth factors were used as ligands for receptor-mediated signaling. The contribution of JAK/STAT3 signaling was defined by the loss-of-function approach with the JAK antagonist, ruxolitinib. In these assays, impairment in ATM-related DNA damage response following acetaminophen toxicity was ameliorated by selected growth factors, including fibroblast growth factors, granulocyte colony stimulating factor and vascular endothelial growth factor. The JAK/STAT3 signaling was exclusive to granulocyte colony stimulating factor but concerned additional pathways in cases of other growth factors. Antagonism of JAK/STAT3 by ruxolitinib abrogated benefits in ATM pathway-mediated DNA repair; and identification of the ruxolitinib-sensitive component of cytoprotection allowed separations of these pathway intersections. Therefore, this subtractive approach for ATM and other regulators in pathways will be informative for DNA damage response. These mechanisms will benefit therapeutic development for ATM-related tissue and organ injuries.

Six-Step Total Synthesis of (±)-Conolidine

A concise total synthesis of (±)-conolidine, a potent nonopioid analgesic, in 19% overall yield is described here. A gold(I)-catalyzed Conia-ene reaction (Toste cyclization) and a Pictet-Spengler reaction served as key transformations for assembling the 1-azabicyclo[4.2.2]decane core and defining the geometry of the exocyclic double bond. The activation energies of formation of the vinyl-gold intermediates were calculated and revealed a silyl enol ether with an unprotected indole moiety as a suitable precursor for the Toste cyclization. This six-step synthesis did not involve any nonstrategic redox manipulations.

Antinociceptive Activity of Petroleum Ether Fraction of Clinacanthus nutans Leaves Methanolic Extract: Roles of Nonopioid Pain Modulatory Systems and Potassium Channels

Methanolic extract of Clinacanthus nutans Lindau leaves (MECN) has been reported to exert antinociceptive activity. The present study aimed to elucidate the possible antinociceptive mechanisms of a lipid-soluble fraction of MECN, which was obtained after sequential extraction in petroleum ether. The petroleum ether fraction of C. nutans (PECN), administered orally to mice, was (i) subjected to capsaicin-, glutamate-, phorbol 12-myristate 13-acetate-, bradykinin-induced nociception model; (ii) prechallenged (intraperitoneal (i.p.)) with 0.15 mg/kg yohimbine, 1 mg/kg pindolol, 3 mg/kg caffeine, 0.2 mg/kg haloperidol, or 10 mg/kg atropine, which were the respective antagonist of α 2-adrenergic, β-adrenergic, adenosinergic, dopaminergic, or muscarinic receptors; and (iii) prechallenged (i.p.) with 10 mg/kg glibenclamide, 0.04 mg/kg apamin, 0.02 mg/kg charybdotoxin, or 4 mg/kg tetraethylammonium chloride, which were the respective inhibitor of ATP sensitive-, small conductance Ca2+-activated-, large conductance Ca2+-activated-, or nonselective voltage-activated-K+ channel. Results obtained demonstrated that PECN (100, 250, and 500 mg/kg) significantly (P<0.05) inhibited all models of nociception described earlier. The antinociceptive activity of 500 mg/kg PECN was significantly (P<0.05) attenuated when prechallenged with all antagonists or K+ channel blockers. However, only pretreatment with apamin and charybdotoxin caused full inhibition of PECN-induced antinociception. The rest of the K+ channel blockers and all antagonists caused only partial inhibition of PECN antinociception, respectively. Analyses on PECN's phytoconstituents revealed the presence of antinociceptive-bearing bioactive compounds of volatile (i.e., derivatives of γ-tocopherol, α-tocopherol, and lupeol) and nonvolatile (i.e., cinnamic acid) nature. In conclusion, PECN exerts a non-opioid-mediated antinociceptive activity involving mainly activation of adenosinergic and cholinergic receptors or small- and large-conductance Ca2+-activated-K+ channels.

p-Cymene attenuates cancer pain via inhibitory pathways and modulation of calcium currents

BACKGROUND

Oncological pain is one of the most prevalent and difficult-to-treat symptoms in patients with cancer. p-Cymene (PC) is a monoterpene found in more than 100 different plant species, endowed with various pharmacological properties-particularly antinociceptive.

HYPOTHESIS/PURPOSE

PC has antinociceptive effect in a model of oncologic pain due to the activation of the descending inhibitory pathway of pain.

STUDY DESIGN

A pre-clinical, longitudinal, blind and randomized study.

METHODS

Male Swiss mice were induced with S180 cells in the right hind paw, then treated daily with PC (12.5, 25 and 50 mg/kg, s.c.) and screened for mechanical hyperalgesia, spontaneous nociception, nociception induced by non-noxious palpation, tumor growth, changes in the neuromuscular function and existence of bone degradation in the tumor area. The effect of PC on Ca²⁺ currents (electrophysiological records), histological and neurochemical changes (immunofluorescence for Fos) were also evaluated.

RESULTS

PC reduced (p < 0.05) the mechanical hyperalgesia, the spontaneous (p < 0.001) and non-noxious palpation (p < 0.001) nociceptions, not changing the tumor development, neuromuscular function or histopathological aspects of the paw affected. PC reduced Fos expression in the spinal cord (p < 0.001) and increased this expression in the PAG (p < 0.05) and in the NRM (p < 0.01). PC decreased the density of calcium channel currents (p < 0.05).

CONCLUSION

These results suggest the antinociceptive effect of PC on oncologic pain, probably acting in both ascending and descending pain pathways, and modulating the calcium channel currents in order to exert its effects.

A new cationic palladium(II) dithiocarbamate exhibits anti-inflammatory, analgesic, and antipyretic activities through inhibition of inflammatory mediators in in vivo models

Inflammation is being a protective mechanism of the body towards the injury. However, chronic and progressive inflammation may lead to some chronic diseases. Due to the serious unwanted effects associated with available drugs, new and safe anti-inflammatory agents are still required. Therefore, the present study was designed to investigate the anti-inflammatory, analgesics, and antipyretic properties of a new compound (4-benzylpiperidine-1-carbodithioato-κ2S,S')(1,4-bis-(diphenylphosphino)butane)palladium(II)chloride monohydrate (compound-1) in albino mice models. Compound-1 was characterized by elemental analysis, FT-IR, and multinuclear NMR spectroscopy. Initially, compound-1 was evaluated for cytotoxicity, anti-inflammatory, and analgesic activities by performing MTT assay, carrageenan-, histamine-, serotonin-, and CFA-induced paw edema, mechanical hyperalgesia, thermal hyperalgesia, and mechanical allodynia (0.1, 1, and 10 mg/kg, b.w). Antipyretic activity was evaluated in brewer's yeast-induced model. The pro-inflammatory cytokines were measured by using commercially available ELISA kits. Additionally, nitrite production, antioxidant enzymes, H&E staining, muscle activity and motor coordination, and kidney and liver function tests were also determined. The results demonstrated that compound-1 significantly inhibited inflammation, pain, and febrile responses in all models at a dose of 10 mg/kg without effecting viability of cells in vitro at concentrations up to 100 μM. Similarly, the data clearly demonstrated significant reduction in the pro-inflammatory cytokines and nitrite production while enhancing antioxidant enzymes. Furthermore, pretreatment with compound-1 did not produce any prominent side effect on kidney, liver, stomach, and muscles. These findings suggest that compound-1 has potent anti-inflammatory-, pain-, and pyrexia-relieving properties. Hence, compound-1 might be a potential candidate for the therapeutic management of chronic inflammation and pain.

The Hemodynamic Effect of Intravenous Paracetamol in Children: A Retrospective Chart Review

AIM

Studies in adults have reported frequent episodes of blood pressure drops following intravenous paracetamol administration. We aimed to investigate the hemodynamic effects of intravenous paracetamol in critically ill children.

METHODS

The charts of 100 pediatric intensive care patients (age range 0.1-18 years) who were treated with intravenous paracetamol between March and September 2017 were retrospectively reviewed. A hemodynamic event was defined as a drop of > 15% in systolic or mean arterial blood pressure within 120 min after drug administration. Hypotension was defined as either a drop in systolic blood pressure (SBP) below the 5th percentile for age or a hemodynamic event associated with tachycardia, increased lactate level, or treatment with a fluid bolus or vasopressors.

RESULTS

A hemodynamic event was observed in 39 patients (39%). In these patients, SBP was in the pre-hypertension or hypertension values in 36/39 patients before paracetamol administration, median (IQR) SBP decreased from the 99th (95-99) percentile for age before to the 50th (50-95) percentile after paracetamol (p < 0.001) and mean heart rate was 137 bpm before treatment and 115 bpm after (p = 0.002). SBP values did not drop below the 5th percentile in any patient. In 15 patients diagnosed with shock on admission, paracetamol treatment did not cause an increase in vasopressor treatment after drug administration.

CONCLUSIONS

In the present study of critically ill pediatric patients, intravenous paracetamol administration was associated with a drop in SBP from high to normal values for age, possibly due to pain relief, with no evidence for a negative hemodynamic event.

Effects of dexmedetomidine and thymoquinone on erythrocyte deformability in lower limb ischemia reperfusion injury in streptozotocin-induced diabetic rats

OBJECTIVE

In this study we aimed to evaluate the effect of dexmedetomidine and thymoquinone on erythrocyte deformability in lower limb ischaemia-reperfusion (IR) injury in streptozotocin-induced diabetic rats.

MATERIAL AND METHODS

Thirty Wistar albino rats were equally divided into 5 groups (n = 6); randomized control group (Group C), diabetes control group (Group DC), DIR group (Group DIR), DIR group with thymoquinone 25 mg.kg‒1 intraperitoneally (Group DIRT) and Group DIR with dexmedetomidine 100 µg.kg‒1 intraperitoneally (Group DIRD). Erythrocyte packs were prepared from heparinized blood samples and deformability measurements were performed.

RESULTS

IR significantly increased the relative resistance, a marker of erythrocyte deformability when compared to control group (p < 0.05). There were significant differences among the groups in comparisons with ANOVA test (p < 0.0001). Comparisons of the groups DIRD and DIRT revealed similar results (p = 0.824). The values of Group DIR were significantly higher than those of the control, DC, DIRD and DIRT groups (p < 0.0001, p = 0.001, p = 0.004, p = 0.002, respectively). The values of the DC, DIR, DIRD and DIRT groups were significantly higher than those of the control group (p < 0.0001, all).

CONCLUSION

Erythrocyte deformability may cause more problems in microcirculation. Dexmedetomidine and thymoquinone may be useful in reducing the adverse effects of this type of injury (Fig. 1, Ref. 41).

Tetrahydrocannabinol Reduces Hapten-Driven Mast Cell Accumulation and Persistent Tactile Sensitivity in Mouse Model of Allergen-Provoked Localized Vulvodynia

Vulvodynia is a remarkably prevalent chronic pain condition of unknown etiology. An increase in numbers of vulvar mast cells often accompanies a clinical diagnosis of vulvodynia and a history of allergies amplifies the risk of developing this condition. We previously showed that repeated exposures to oxazolone dissolved in ethanol on the labiar skin of mice led to persistent genital sensitivity to pressure and a sustained increase in labiar mast cells. Here we sensitized female mice to the hapten dinitrofluorobenzene (DNFB) dissolved in saline on their flanks, and subsequently challenged them with the same hapten or saline vehicle alone for ten consecutive days either on labiar skin or in the vaginal canal. We evaluated tactile ano-genital sensitivity, and tissue inflammation at serial timepoints. DNFB-challenged mice developed significant, persistent tactile sensitivity. Allergic sites showed mast cell accumulation, infiltration of resident memory CD8⁺CD103⁺ T cells, early, localized increases in eosinophils and neutrophils, and sustained elevation of serum Immunoglobulin E (IgE). Therapeutic intra-vaginal administration of Δ⁹-tetrahydrocannabinol (THC) reduced mast cell accumulation and tactile sensitivity. Mast cell-targeted therapeutic strategies may therefore provide new ways to manage and treat vulvar pain potentially instigated by repeated allergenic exposures.

The paracetamol metabolite N-acetylp-benzoquinone imine reduces excitability in first- and second-order neurons of the pain pathway through actions on KV7 channels

Paracetamol (acetaminophen, APAP) is one of the most frequently used analgesic agents worldwide. It is generally preferred over nonsteroidal anti-inflammatory drugs because it does not cause typical adverse effects resulting from the inhibition of cyclooxygenases, such as gastric ulcers. Nevertheless, inhibitory impact on these enzymes is claimed to contribute to paracetamols mechanisms of action which, therefore, remained controversial. Recently, the APAP metabolites N-arachidonoylaminophenol (AM404) and N-acetyl-p-benzoquinone imine (NAPQI) have been detected in the central nervous system after systemic APAP administration and were reported to mediate paracetamol effects. In contrast to nonsteroidal anti-inflammatory drugs that rather support seizure activity, paracetamol provides anticonvulsant actions, and this dampening of neuronal activity may also form the basis for analgesic effects. Here, we reveal that the APAP metabolite NAPQI, but neither the parent compound nor the metabolite AM404, reduces membrane excitability in rat dorsal root ganglion (DRG) and spinal dorsal horn (SDH) neurons. The observed reduction of spike frequencies is accompanied by hyperpolarization in both sets of neurons. In parallel, NAPQI, but neither APAP nor AM404, increases currents through KV7 channels in DRG and SDH neurons, and the impact on neuronal excitability is absent if KV7 channels are blocked. Furthermore, NAPQI can revert the inhibitory action of the inflammatory mediator bradykinin on KV7 channels but does not affect synaptic transmission between DRG and SDH neurons. These results show that the paracetamol metabolite NAPQI dampens excitability of first- and second-order neurons of the pain pathway through an action on KV7 channels.

Nociceptin/orphanin FQ receptor ligands and translational challenges: focus on cebranopadol as an innovative analgesic

Opioids are characterised as classical (mu, delta, and kappa) along with the non-classical nociceptin/orphanin FQ (N/OFQ) receptor or NOP. Targeting NOP has therapeutic indications in control of the cardiovascular and respiratory systems and micturition, and a profile as an antidepressant. For all of these indications, there are translational human data. Opioids such as morphine and fentanyl (activating the mu receptor) are the mainstay of pain treatment in the perioperative period, despite a challenging side-effect profile. Opioids in general have poor efficacy in neuropathic pain. Moreover, longer term use is associated with tolerance. There is good evidence interactions between opioid receptors, and receptor co-activation can reduce side-effects without compromising analgesia; this is particularly true for mu and NOP co-activation. Recent pharmaceutical development has produced a mixed opioid/NOP agonist, cebranopadol. This new chemical entity is effective in animal models of nociceptive and neuropathic pain with greater efficacy in the latter. In animal models, there is little evidence for respiratory depression, and tolerance (compared with morphine) only develops after long treatment periods. There is now early phase clinical development in diabetic neuropathy, cancer pain, and low back pain where cebranopadol displays significant efficacy. In 1996, N/OFQ was formally identified with an innovative analgesic profile. Approximately 20 yr later, cebranopadol as a clinical ligand is advancing through the human trials process.

Acetaminophen enhances the reflective learning process

Acetaminophen has been shown to influence cognitive and affective behavior possibly via alterations in serotonin function. This study builds upon this previous work by examining the relationship between acetaminophen and dual-learning systems, comprising reflective (rule-based) and reflexive (information-integration) processing. In a double-blind, placebo-controlled study, a sample of community-recruited adults (N = 87) were randomly administered acetaminophen (1000 mg) or placebo and then completed reflective-optimal and reflexive-optimal category learning tasks. For the reflective-optimal category learning task, acetaminophen compared to placebo was associated with enhanced accuracy prior to the first rule switch (but not overall accuracy), with needing fewer trials to reach criterion and with a faster learning rate. Acetaminophen modestly attenuated performance on the reflexive-optimal category learning task compared to placebo. These findings indirectly support two positions that have been proposed elsewhere. First, they are consistent with the view that acetaminophen has an influence on the serotonergic system. Second, the findings are consistent with a proposed link between elevated serotonin function and relative dominance of effortful, rule-based processing.

Antinociceptive efficacy and respiratory effects of dexmedetomidine in ball pythons (Python regius)

OBJECTIVE To determine antinociceptive efficacy, behavioral patterns, and respiratory effects associated with dexmedetomidine administration in ball pythons (Python regius). ANIMALS 12 ball pythons. PROCEDURES Antinociception was assessed by applying an infrared heat stimulus to the cranioventral surface of snakes during 2 experiments. Thermal withdrawal latency was measured at 0, 2, and 24 hours after SC injections of dexmedetomidine (0.1 or 0.2 mg/kg) or saline (0.9% NaCl) solution and at 0 to 60 minutes after injection of dexmedetomidine (0.1 mg/kg) or saline solution. Behaviors were recorded at 0, 2, and 24 hours after administration of dexmedetomidine (0.1 mg/kg) or saline solution. Tongue flicking, head flinch to the approach of an observer's hand, movement, and righting reflex were scored. Respiratory frequency was measured by use of plethysmography to detect breathing-related movements after injection of dexmedetomidine (0.1 mg/kg) or saline solution. RESULTS Mean baseline withdrawal latency was 5 to 7 seconds; saline solution did not alter withdrawal latency. Dexmedetomidine increased withdrawal latency by 18 seconds (0.2 mg/kg) and 13 seconds (0.1 mg/kg) above baseline values at 2 hours. Increased withdrawal latency was detected within 15 minutes after dexmedetomidine administration. At 2 hours after injection, there were few differences in behavioral scores. Dexmedetomidine injection depressed respiratory frequency by 55% to 70%, compared with results for saline solution, but snakes continued to breathe without prolonged apnea. CONCLUSIONS AND CLINICAL RELEVANCE Dexmedetomidine increased noxious thermal withdrawal latency without causing excessive sedation. Therefore, dexmedetomidine may be a useful analgesic drug in ball pythons and other snake species.

Antiallodynic Effects of Intrathecal Areca Nut for Spinal Nerve-Ligated and Chemotherapy-Induced Neuropathic Pain in Rats

This study examined the effects of intrathecal areca nut on spinal nerve-ligated and chemotherapy-induced neuropathic pain (NP), and investigated the relevance of spinal 5-hydroxytryptamine (5-HT) and α2-adrenergic receptors to those effects. For drug administration, intrathecal catheters were inserted into the subarachnoid space of male Sprague-Dawley rats. NP was induced either by spinal nerve ligation (left spinal nerves L5 and L6) or by chemotherapeutic injection (intraperitoneal cisplatin, 2 mg/kg/day, once daily for 4 days). Paw withdrawal thresholds (PWT) were mechanically assessed using von Frey filaments. The involvement of 5-HT and α2-adrenergic receptors in antiallodynia was determined using antagonists with the following receptor specificities: nonselective 5-HT (dihydroergocristine), 5-HT7 (SB269970), nonselective α2-adrenoceptor (yohimbine), α-2A (BRL 44408), α-2B (ARC 239), and α-2C (JP 1302). Intrathecal areca nut significantly increased the PWT in both spinal nerve-ligated and chemotherapy-induced NP (‡ p < 0.001). Intrathecal dihydroergocristine, SB269970, yohimbine, BRL 44408, ARC 239, and JP 1302 significantly reversed the antiallodynic effects of areca nut in both NP states (‡ p < 0.001). Collectively, intrathecal areca nut suppressed mechanical allodynia induced by spinal nerve ligation and cisplatin injection. Furthermore, spinal 5-HT7 receptor and α2A, α2B, and α2C-adrenoceptors contributed to the antiallodynic effects of areca nut.

The Influence of Acetaminophen and Observational Conditioning on the Acquired Capability for Suicide

The effects of acetaminophen and a reading task on physical pain tolerance and fearlessness about death were tested in 106 undergraduate students. Participants were randomized into four groups, each receiving either acetaminophen or no medication, along with either a control or experimental reading task. It was predicted that acetaminophen would increase pain tolerance and fearlessness about death, that the experimental reading task would decrease both outcomes, and that the interventions would interact (i.e., acetaminophen would dampen the effects of the reading task). Multivariate analysis of variance was used to test hypotheses. No significant interaction was found (p = .17) and there was no effect for acetaminophen (p = .56), but individuals administered the experimental reading task demonstrated significantly higher physical pain tolerance (p < .05).

A new bioluminescent imaging technology for studying oxidative stress in the testis and its impacts on fertility

PURPOSE

Excessive oxidative stress (OS) leads to cellular dysfunctions and cell death and constitutes a major cause of male infertility. However, the etiologies of increased reactive oxygen species (ROS) in male infertility is not fully understood. One major limitation is the lack of an in vivo imaging system that can be used to effectively study the impact of excessive ROS in the testis. Recently, we discovered that the hepatocellular carcinoma reporter (HCR) mice previously generated in our laboratory also expressed luciferase in the spermatids of the testis. The goal of the current study is to use the HCR mice to detect OS in the testis and to investigate the potential use of this new system in studying OS-induced male infertility.

EXPERIMENTAL DESIGN

Bioluminescence imaging (BLI) was performed in HCR mice that were treated with peroxy caged luciferin-1 (PCL-1), an OS reporter, to establish a new mouse model for in vivo monitoring of the OS status inside the male reproductive tract. Subsequently, the effect of acetaminophen (APAP) overdose on the OS inside the testis and male fertility were determined. Lastly, APAP was co-administered with glutathione, an antioxidant reagent, to test if the HCR mice can serve as a model for the effective and rapid assessment of the potency of individual agents in modifying the OS inside the mouse testis.

RESULTS

The OS level in the testis in the HCR mice was readily detected by BLI. The use of this new model led to the discovery that APAP caused a sudden rise of OS in the testis and was a potent toxicant for the male reproductive system. Moreover, administration of glutathione was effective in preventing the APAP-induced elevation of OS and in ameliorating all of the OS-induced anomalies in the testis.

CONCLUSIONS

The HCR mice represent an excellent model for monitoring OS change in the mouse testis by real time BLI. APAP is a potent male reproductive toxicant and APAP-treated mice represent a valid model for OS-induced male infertility. This model can be used to study OS-induced damage in male reproductive tract and in assessing the effects of therapeutic agents on the relative levels of OS and male fertility.

Effects of opioid- and non-opioid analgesics on responses to psychosocial stress in humans

Both preclinical and clinical evidence suggests that the endogenous opioid system is involved in responses to stress. For example, in animal models opioid agonists reduce isolation distress whereas opioid antagonists increase isolation distress. We recently reported that the mixed mu agonist and kappa antagonist buprenorphine dampened responses to acute psychosocial stress in humans. Now we extend this to study the effects of a pure mu-opioid agonist, hydromorphone, and a non-opioid analgesic, acetaminophen, on response to social stress. We compared the effect of hydromorphone (2 and 4 mg), acetaminophen (1000 mg) to a placebo using a between subject design. Healthy adult volunteers were randomly assigned to receive placebo (N = 13), 2 mg hydromorphone (N = 12), 4 mg hydromorphone (N = 12), or 1000 mg acetaminophen (paracetamol; N = 13) under double-blind conditions before undergoing a stress task or a control task on two separate sessions. The stress task, consisting of a standardized speaking task and the non-stressful control task were presented in counterbalanced order. Dependent measures included mood ratings, subjective appraisal of the stress (or no-stress) task, salivary cortisol, pupil diameter, heart rate, and blood pressure. The stress task produced its expected increase in heart rate, blood pressure, salivary cortisol, pupil diameter, and subjective ratings of anxiety and negative mood. Hydromorphone dose-dependently dampened cortisol responses to stress, and decreased ratings of how "challenging" participants found the task. Acetaminophen did not affect physiological responses, but, like hydromorphone, decreased ratings of how "challenging" the task was. The hydromorphone results support the idea that the mu-opioid system is involved in physiological responses to acute stress in humans, in line with results from preclinical studies. The non-opioid analgesic acetaminophen did not dampen physiological responses, but did reduce some components of psychological stress. It remains to be determined how both opioid and non-opioid systems mediate the complex physiological and psychological responses to social stress.

CONSORT-epidural dexmedetomidine improves gastrointestinal motility after laparoscopic colonic resection compared with morphine

BACKGROUND

We have previously shown that epidural dexmedetomidine, when used as an adjunct to levobupivacaine for control of postoperative pain after open colonic resection, improves recovery of gastrointestinal motility compared with morphine.

METHODS

Sixty patients undergoing laparoscopic colonic resection were enrolled and allocated randomly to treatment with dexmedetomidine (group D) or morphine (group M). Group D received an epidural loading dose of dexmedetomidine (5 mL, 0.5 μg/kg), followed by continuous epidural administration of dexmedetomidine (80 μg) in 0.125% levobupivacaine (240 mL) at a rate of 5 mL/h for 2 days. Group M received an epidural loading dose of morphine (5 mL, 0.03 mg/kg) followed by continuous epidural administration of morphine (4.5 mg) in 0.125% levobupivacaine (240 mL) at a rate of 5 mL/h for 2 days. Verbal rating score (VRS) of pain, postoperative analgesic requirements, side effects related to analgesia, and time to postoperative first flatus (FFL) and first feces (FFE) were recorded.

RESULTS

VRS and postoperative analgesic requirements were not significantly different between the treatment groups. In contrast, FFL and FFE were significant delayed in group M compared with group D (P < .05). Patients in group M also had a significantly higher incidence of nausea, vomiting, and pruritus (P < .05). No neurological deficits were observed in either group.

CONCLUSIONS

Compared with morphine, epidural dexmedetomidine is a better adjunct to levobupivacaine for control of postoperative pain after laparoscopic colonic resection.

Suppression of HDAC2 in Spinal Cord Alleviates Mechanical Hyperalgesia and Restores KCC2 Expression in a Rat Model of Bone Cancer Pain

Epigenetic modulation participates in the mechanism of multiple types of pathological pain, so targeting the involved regulators may be a promising strategy for pain treatment. Our previous research identified the analgesic effect of the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) on mechanical hyperalgesia in a rat model of bone cancer pain (BCP) via restoration of μ-opioid receptor (MOR) expression. However, the specific types of HDACs contributing to BCP have not been explored. The present study investigated the expression pattern of some common HDACs and found that HDAC2 was up-regulated in a time-dependent manner in the lumbar spinal cord of BCP rats. TSA application suppressed HDAC2 expression in cultured PC12 cells and reversed the augmented HDAC2 in BCP rats. An RNA-interfering strategy confirmed the essential role of HDAC2 in the modulation of mechanical hyperalgesia following tumor cell inoculation, and we further examined its possible downstream targets. Notably, HDAC2 knock-down did not restore MOR expression, but it robustly reversed the down-regulation of potassium-chloride cotransporter 2 (KCC2). The impaired KCC2 expression is a vital mechanism of many types of pathological pain. Therefore, our results demonstrated that HDAC2 in spinal cord contributed to the mechanical hyperalgesia in BCP rats, and this effect may be associated with KCC2 modulation.

Increased ethanol drinking in "humanized" mice expressing the mu opioid receptor A118G polymorphism are mediated through sex-specific mechanisms

The A118G single nucleotide polymorphism (SNP) of the mu-opioid receptor gene (Oprm1) has been implicated in mediating the rewarding effects of alcohol. Clinical and preclinical studies suggest that the G allele may confer a genetic vulnerability to alcohol dependence, though it remains unknown whether these effects are sex-specific. We used male and female mice homozygous for the "humanized" 118AA or 118GG alleles to determine whether the A118G SNP potentiates ethanol consumption in a sex-specific manner in both the two-bottle choice and drinking-in-the-dark (DID) paradigms. Mice were also assessed for differences in naltrexone sensitivity, ethanol reward assessed via conditioned place preference (CPP), and sensitivity to the sedative/ataxic effects of ethanol using the rota-rod and loss of righting reflex (LORR) assays. We found that male and female 118GG mice drank significantly more ethanol than 118AA littermates using a continuous access, two-bottle choice paradigm. In the limited-access DID drinking model, (i) female (but not male) 118GG mice consumed more ethanol than 118AA mice and (ii) naltrexone pretreatment was equally efficacious at attenuating ethanol intake in both 118AA and 118GG female mice while having no effect in males. Male and female 118GG and female 118AA mice developed a robust conditioned place preference (CPP) for ethanol. Female 118GG mice displayed less sensitivity to the sedative/ataxic effects of ethanol compared to female 118AA mice on both the rota-rod and the LORR assays while male mice did not differ in their responses on either assay. Our findings suggest that increased ethanol consumption in male 118GG mice may be due to increased ethanol reward, while increased drinking in female 118GG mice might be due to decreased sensitivity to the sedative/ataxic effects of ethanol. Collectively, these data might be used to help identify sex-specific pharmacotherapies to combat alcohol use disorders.

Responsiveness of rat fetuses to sibling motor activity: Communication in utero?

Previous research has revealed that fetuses detect and respond to extrauterine stimuli such as maternal movement and speech, but little attention has been cast on how fetuses may directly influence and respond to each other in the womb. This study investigated whether motor activity of E20 rat fetuses influenced the behavior of siblings in utero. Three experiments showed that; (a) contiguous siblings expressed a higher frequency of synchronized movement than noncontiguous siblings; (b) fetuses that lay between two siblings immobilized with curare showed less movement relative to fetuses between saline or uninjected controls; and (c) fetuses between two siblings behaviorally activated by the opioid agonist U50,488 also showed less activity and specific behavioral changes compared to controls. Our findings suggest that rat fetuses are directly impacted by sibling motor activity, and thus that a rudimentary form of communication between siblings may influence the development of fetuses in utero.