Effects Of Naloxone Research Articles

Naloxone Ameliorates Spatial Memory Deficits and Hyperthermia Induced by a Neurotoxic Methamphetamine Regimen in Male Rats.

Background: Methamphetamine (METH) as a synthetic psychostimulant is being increasingly recognized as a worldwide problem, which may induce memory impairment. On the other hand, it is well established that naloxone, an opiate antagonist, has some beneficial effects on learning and memory. The present research aimed at evaluating naloxone effects on spatial learning and memory impairment triggered by a neurotoxic regimen of METH in male rats. Materials and Methods: The animals received the subcutaneous (sc) regimen of METH (4×6 mg/kg at 2-h intervals), intraperitoneal (ip) naloxone (4×1 mg/kg at 2-h intervals), or normal saline at four events. The Nal-METH group of rats received four naloxone injections (1 mg/ kg, ip) 30 min before each METH injection (6 mg/kg, sc) at 2-h intervals. Seven days later, they were evaluated for spatial learning and memory in the Morris Water Maze (MWM) task. Results: METH regimen induced hyperthermia, as well as a poor performance, in the acquisition and retention phases of the task, indicating spatial learning and memory impairment compared to the controls. Naloxone administration (1 mg/kg, ip) before each METH injection led to significant attenuations of both hyperthermia and METH adverse effects on the rat performance in the MWM task. Conclusion: The results revealed that pretreatment with the opiate antagonist naloxone could prevent METH adverse effects on body temperature and memory performance. It seems that the opioidergic system and hyperthermia may, at least partially, be involved in METH effects on spatial memory.

Naloxone Ameliorates Spatial Memory Deficits and Hyperthermia Induced by a Neurotoxic Methamphetamine Regimen in Male Rats

Background: Methamphetamine (METH) as a synthetic psychostimulant is being increasingly recognized as a worldwide problem, which may induce memory impairment. On the other hand, it is well established that naloxone, an opiate antagonist, has some beneficial effects on learning and memory. The present research aimed at evaluating naloxone effects on spatial learning and memory impairment triggered by a neurotoxic regimen of METH in male rats. Materials and Methods: The animals received the subcutaneous (sc) regimen of METH (4×6 mg/kg at 2-h intervals), intraperitoneal (ip) naloxone (4×1 mg/kg at 2-h intervals), or normal saline at four events. The Nal-METH group of rats received four naloxone injections (1 mg/kg, ip) 30 min before each METH injection (6 mg/kg, sc) at 2-h intervals. Seven days later, they were evaluated for spatial learning and memory in the Morris Water Maze (MWM) task. Result: METH regimen induced hyperthermia, as well as a poor performance, in the acquisition and retention phases of the task, indicating spatial learning and memory impairment compared to the controls. Naloxone administration (1 mg/kg, ip) before each METH injection led to significant attenuations of both hyperthermia and METH adverse effects on the rat performance in the MWM task. Conclusion: The results revealed that pretreatment with the opiate antagonist naloxone could prevent METH adverse effects on body temperature and memory performance. It seems that the opioidergic system and hyperthermia may, at least partially, be involved in METH effects on spatial memory. [GMJ. 2019;8:e1182]

Methocinnamox (MCAM) is a Selective, Long Acting Antagonist at Mu Opioid Receptors In Vitro

The occurrence of opioid overdose is reaching epidemic proportions; an estimated 115 Americans die daily from an opioid overdose. The current pharmacological treatment relies exclusively on naloxone (Narcan), a competitive antagonist at mu opioid receptors, that can reverse the respiratory depression and sedation produced by opioid agonists like heroin and fentanyl. However, naloxone's effectiveness is limited by its short half‐life. By contrast, methocinnamox (MCAM) has been shown to be a long‐acting mu opioid receptor antagonist and as such, may be more effective for reversing opioid overdose. However, rigorous characterization of the pharmacological properties of MCAM has not yet been done. Here we characterized the antagonist properties of MCAM using HEK cell lines that stably express either human mu, delta or kappa opioid receptors along with a bioluminescent cAMP sensor. Opioid receptor agonist concentration response curves were obtained in response to either DAMGO (mu agonist), DPDPE (delta agonist) or U50488 (kappa agonist) for inhibition of forskolin‐stimulated cellular cAMP levels.We first compared MCAM to that of naloxone at mu receptors. Incubation with the mu receptor agonist DAMGO inhibited forskolin‐stimulated cAMP levels by 40% ± 2 % with an EC50 of 10 nM. Pretreatment with MCAM (10 nM, 10 × Ki) for 15 min shifted the concentration response curve (CRC) to DAMGO to the right 1000‐fold and suppressed the maximal response by 50%. The magnitude of MCAM's antagonist effect increased following a 2h pretreatment. Pretreatment with naloxone (NLX, 100 nM, 10 × Ki) for 15 min also antagonized DAMGO‐mediated inhibition of stimulated cAMP levels. However, in contrast to MCAM, the shift in the DAMGO CRC by NLX was fully surmountable and there was no further antagonist effect with 2h of NLX pretreatment. Furthermore, MCAM‐mediated antagonism following a 2h pretreatment was unchanged after a rigorous washout period whereas antagonism produced by NLX was fully reversible. At delta opioid receptors, pretreatment with MCAM (20 nM, 10 × Ki at delta) for either 15 min or 2h shifted the DPDPE CRC ~10‐fold to the right with no change in the maximal response. Similarly, the CRC for the kappa agonist, U50488, was shifted ~10‐fold to the right with no change in the maximal response following pretreatment for either 15 min or 2h with MCAM (50 nM, 10 × Ki at kappa). Furthermore, antagonism produced by MCAM was fully reversible at both delta‐ and kappa opioid receptors.The time‐dependent nature of antagonism, the depression of the maximal mu agonist response, the lack of reversibility following wash‐out, and the lack of long‐term antagonist effects at either delta or kappa opioid receptors suggests that MCAM is a selective, long acting (perhaps irreversible) mu opioid receptor antagonist.Support or Funding InformationSupported by the ARTT Center of Excellence, UT Health San Antonio.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Efficacy of Naloxone as a Treatment for an Acute Exposure to Aerosolized Carfentanil

Carfentanil (CRF) is a powerful synthetic opioid that is approximately 100 times more potent than fentanyl and 10,000 times more potent than morphine. CRF originally was intended to be used as a sedative for big game animals in a veterinary setting, but is becoming increasingly common in the illicit drug trade. The increased use of CRF by people has put strain on first responders, who need to administer increased doses of naloxone (Naracan®, Evzio®), an FDA‐approved opioid antagonist, to counteract the effects. First responders may also worry about the potential of self‐exposure through inhalation or dermal contact with CRF. We set out to study the effectiveness of naloxone against a potentially lethal dose of inhaled CRF in male ferrets. Ferrets were implanted with telemetry devices to study cardiac parameters and exposed to aerosolized CRF in a whole‐body plethysmography chamber to record respiratory parameters. We observed profound depression of respiration which resulted in the animals becoming apneic 23% ± 9% of the time during exposure. We also observed cardiac abnormalities, in the form of premature junctional contractions (PJCs), in the ferrets during the apneic periods. At our acute exposure dose, which was lethal in 9% of our animals, ferrets were unresponsive and incapacitated for 105.6 ± 20.0 minutes following the end of exposure. Naloxone, when administered intramuscularly at human equivalent doses ranging from 4 to 40 mg, significantly reduced the time that ferrets were incapacitated following exposure. Although we saw no significant difference in the reduction of time that the animals were incapacitated between the treatment groups (average times between treatment and revival ranged from 6.5 to 9.7 minutes), higher doses of naloxone did revive a portion of the ferrets quicker than the lower doses (some as soon as 1.5–3.5 minutes post‐treatment). We also observed that naloxone was able to significantly reduce the amount of apneic episodes in CRF‐exposed ferrets and resolved the observed cardiac PJCs. Our results suggest that naloxone is a viable treatment against the effects of a potentially lethal dose of inhaled CRF in ferrets. These data have the potential to inform and aid treatment strategies for an acute inhalation exposure to synthetic opioids.Support or Funding InformationOpinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the US Army. This research complied with the Animal Welfare Act and implementing Animal Welfare Regulations and adhered to the principles noted in The Guide for the Care and Use of Laboratory Animals. This research was supported by DTRA RD‐CB. M.R. and N.A.A. were supported in part by an appointment to the Postgraduate Research Participation Program at the US Army Medical Research Institute of Chemical Defense administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the US Department of Energy and USAMRMC.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

(357) Effect of Naloxone on Touch Intensity and Pleasantness

Both light skin stroking (engaging the C-tactile afferent sensory pathway) and deep pressure touch (as in deep tissue massage) are commonly perceived as pleasant and relaxing. Opioid blockade has been found to increase receipt of grooming in monkeys, suggesting possible opioid modulation of touch pleasantness. Recently, human data [1] suggested that blocking opioid receptors might decrease the perceived intensity of gentle brushing but increase its pleasantness. The current study examined the role of endogenous opioids in the perceived intensity and pleasantness of pleasant touch. Using a double-blind cross-over design, 24 healthy adult participants received intravenous naloxone or saline (control) on separate days. Blocks of gentle brushing and deep pressure compression were administered on the lower left calf. Participants rated the intensity and pleasantness of each stimulus, as well as current mood and anxiety. Naloxone significantly reduced perceived intensity of gentle brushing (p = 0.039), but did not affect brushing pleasantness (p = 0.44) or intensity or pleasantness of deep pressure (p = 0.97; p = 0.85). The naloxone-induced reduction in gentle touch intensity replicates results previously seen in chronic pain patients [1]. The lack of effect on pleasantness in this study versus [1] could relate to differences in the location of touch (arm or leg), sex of the experimenters, or whether the touch followed pain tasks. However, in the current study, naloxone was marginally anxiolytic (p = 0.07), and naloxone-induced changes in touch pleasantness were significantly more correlated with subsequent mood and anxiety ratings than were changes during saline (mood p = 0.04; anxiety p

A Survey on the Adjuvant Role of Naloxone Alone or Combined with Alum in Vaccination Against Fasciolosis in BALB/c Mice.

Fasciolosis is a zoonotic parasitic diseaseimposinga heavy load of livestock losses worldwide. We aimed to evaluate immune-stimulatory effects of naloxone (NLX), an opioid receptor antagonist, in combination with alum in mice vaccinated with excretory-secretory antigens (E/S) of Fasciola hepatica. 8-week-old female BALB/c mice were subcutaneously vaccinated using E/S antigens of F. hepatica. Experimental groups (14 mice per group) included: vaccine (E/S antigen), alum vaccine (E/S antigen plus alum), NLX vaccine (E/S antigen plus NLX), and alum-NLX vaccine (E/S antigen plus a mixture of alum-NLX). The control group was infused with PBS. Lymphocyte proliferation and the levels of IFN-γ, IL-4, IgG2a, IgG1, and total IgG were measured. Mice vaccinated with NLX or alum-NLX adjuvants showed significantly higher rates of lymphocyte proliferation, IFN-γ, total IgG, and IgG2a levels. The mice that were injected with alum showed a significantly higher concentration of IL-4. Ratios of IFN-γ/Il-4 and IgG2a/IgG1 were significantly higher in the NLX and alum-NLX groups in comparison with the groups vaccinated either with alum or without any adjuvant. A significantly higher protection rate (62.5%) was seen in mice vaccinated with the alum-NLX adjuvant compared to the other groups. NLX can be effective in conferring cellular immunity and protection against F. hepatica. It is recommended to consider this agent as a potential adjuvant in vaccines against fasciolosis.

Take-home naloxone and the politics of care.

'Take-home naloxone' refers to a life-saving intervention in which a drug (naloxone) is made available to nonmedically trained people for administration to other people experiencing an opioid overdose. In Australia, it has not been taken up as widely as would be expected, given its life-saving potential. We consider the actions of take-home naloxone, focusing on how care relations shape its uses and effects. Mobilising Science and Technology Studies insights, we suggest that the uses and effects of naloxone are co-produced within social relations and, therefore, this initiative 'affords' multiple outcomes. We argue that these affordances are shaped by a politics of care, and that these politics relate to uptake. We analyse two complementary case studies, drawn from an interview-based project, in which opioid consumers discussed take-home naloxone and its uses. Our analysis maps the ways take-home naloxone can afford (i) a regime of care within an intimate partnership (allowing a terminally ill man to more safely consume opioids) and (ii) a political process of care (in which a consumer takes care of others treated with the medication by administering it 'gently'). We conclude by exploring the political affordances of a politics of care approach for the uptake of take-home naloxone.

Acute and chronic effects of morphine on Low-Mg2+ ACSF-induced epileptiform activity during infancy in mice hippocampal slices.

Interaction of morphine and seizure is complex. Mouse brain hippocampal slices were used to estimate how acute and chronic morphine treatment alters the low-magnesium artificial cerebrospinal fluid (LM-ACSF)-induced seizure activity. Hippocampal slices were taken from the normal and morphine-treated mice. The normal mice received saline while the other group (morphine-treated mice) received morphine daily for 5 consecutive days. Saline/morphine administration was performed subcutaneously (s.c, 0.1 mL) at postnatal days 14-18. Hippocampal slices of all animals were perfused with LM-ACSF followed by different morphine concentrations (0, 10, 100, and 1000 μM) or naloxone (10 μM). Changes in the spike count were considered as indices for quantifying the seizure activity in the slices. In hippocampus of both groups perfused with 10 or 1000 μM morphine, epileptiform activity was suppressed while it was potentiated at 100 μM morphine. The excitatory effect of morphine at 100 μM was stronger in normal mice (acute exposure) than in dependent mice (chronic exposure). Naloxone suppressed the epileptiform activities in both groups. Suppressive effect of naloxone was more significant in morphine-treated mice than in normal mice. The seizure activity in morphine-dependent mice was more labile than that of normal mice. It can be concluded that morphine had a biphasic effect on LM-ACSF-induced epileptiform activities in both groups. The occurrence of seizure was comparable in acute and chronic exposure of morphine but strength of the effect was considerably robust in normal mice. The down regulation of opioid receptors in chronic exposure is likely to be responsible for these differences.

Decrease of inhibitory synaptic currents of locus coeruleus neurons via orexin type 1 receptors in the context of naloxone-induced morphine withdrawal.

Acute opioid withdrawal syndrome is a series of neurological symptoms caused by the abrupt cessation of the chronic administration of opioids such as morphine. The locus coeruleus (LC) in the brain stem receives a dense projection of orexinergic fibers from the hypothalamus and is a candidate site for the expression of the somatic aspects of morphine withdrawal. Previous studies have shown that orexin-A contributes to the behavioral symptoms of naloxone-induced morphine withdrawal, partly by reducing the activity of GABAergic neurons, suggesting that orexin-A may negatively modulate fast GABAergic neurotransmission during morphine withdrawal. We used whole-cell patch-clamp recordings of LC neurons in brainstem slices to investigate the effect of orexin-A on bicuculline-sensitive GABAergic inhibitory postsynaptic currents (IPSCs) during naloxone-induced morphine withdrawal. Male Wistar rats (P14-P21) were given morphine (20mg/kg, i.p.) daily for seven consecutive days to create dependency on the drug. The application of naloxone (1µM) to brain slices of morphine-treated rats reduced the amplitude of evoked IPSCs (eIPSCs) as well as spontaneous IPSCs (sIPSCs) frequency but did not change sIPSCs amplitude. Orexin-A (100nM) significantly enhanced the suppressive effect of naloxone on eIPSCs amplitude and sIPSCs frequency but had no effect on the presence of the orexin type 1 receptor (OX1R) antagonist, SB-334867. Orexin-A alone had no significant effect on eIPSCs and sIPSCs in the absence of naloxone. In summary, our results show that orexin-A, via OX1R, potentiates the suppressive effect of naloxone on GABAergic IPSCs of LC neurons in morphine-treated rats. We conclude that orexins may have a critical role in regulating GABAergic neurotransmission to LC neurons during naloxone-induced morphine withdrawal.

Naloxone for opioid-exposed newborn infants.

Naloxone, a specific opioid antagonist, is available for the treatment of newborn infants with cardiorespiratory or neurological depression that may be due to intrauterine exposure to opioid. It is unclear whether newborn infants may benefit from this therapy and whether naloxone has any harmful effects. To determine the effect of naloxone on the need for and duration of neonatal unit stay in infants of mothers who received opioid analgesia prior to delivery or of mothers who have used a prescribed or non-prescribed opioid during pregnancy. We searched the following databases in February 2018: the Cochrane Central Register of Controlled Trials (the Cochrane Library 2018, Issue 1), MEDLINE (OvidSP), MEDLINE In process & Other Non-Indexed Citations (OvidSP), Embase (OvidSP), CINAHL (EBSCO), Maternity and Infant Care (OvidSP), and PubMed. We searched for ongoing and completed trials in the WHO International Clinical Trials Registry Platform and the EU Clinical Trials Register. We checked the reference lists of relevant articles to identify further potentially relevant studies. Randomised controlled trials comparing the administration of naloxone versus placebo, or no drug, or another dose of naloxone to newborn infants with suspected or confirmed in utero exposure to opioid. We extracted data using the standard methods of Cochrane Neonatal with separate evaluation of trial quality and data extraction by two review authors and synthesis of data using risk ratio, risk difference, and mean difference. We included nine trials, with 316 participants in total, that compared the effects of naloxone versus placebo or no drug in newborn infants exposed to maternal opioid analgesia prior to delivery. None of the included trials investigated infants born to mothers who had used a prescribed or non-prescribed opioid during pregnancy. None of these trials specifically recruited infants with cardiorespiratory or neurological depression. The main outcomes reported were measures of respiratory function in the first six hours after birth. There is some evidence that naloxone increases alveolar ventilation. The trials did not assess the effect on the primary outcomes of this review (admission to a neonatal unit and failure to establish breastfeeding). The existing evidence from randomised controlled trials is insufficient to determine whether naloxone confers any important benefits to newborn infants with cardiorespiratory or neurological depression that may be due to intrauterine exposure to opioid. Given concerns about the safety of naloxone in this context, it may be appropriate to limit its use to randomised controlled trials that aim to resolve these uncertainties.

Effects of orexin-A on firing activity of gastric distension-sensitive neurons in the basomedial amygdala and food intake in diet-induced obese rats

Objective To investigate the effects of orexin-A on firing activity of gastric distension-sensitive (GD) neurons in the basomedial amygdala (BMA) and food intake in diet-indaced obese rats. Methods Healthy male Wistar rats were selected, and the diet-induced obesity (DIO) rat model and diet-induced resistant (DR) rat model were established by high-fat diet. The effects of orexin-A and an opioid receptor antagonist naloxone on BMA GD neurons were observed by recording the extracellular potentials of single neurons.The effects of orexin-A and naloxone on the food intake of different rats were observed by using BMA catheterization.The mRNA expression and protein expression of orexin-1 receptor (OX-1R) and μ opioid receptor were detected by real-time PCR and Elisa, respectively. Results After microinjection of orexin-A into the BMA, the firing frequency of GD-sensitive neurons in the normal rats was significantly increased (GD-E: (78.3±6.9)%, GD-I: (55.5±4.7)%, P<0.01), and this effect was completely blocked by OX-1R receptor antagonist SB334867, and naloxone partially blocked the discharge-promoting effect of orexin-A; Compared with the normal rats, the firing frequency of GD-sensitive neurons in the DIO(GD-E: (91.6±7.1)%, GD-I: (67.9±8.1)%) and DR(GD-E: (87.9±6.8)%, GD-I: (69.2±5.8)%)rats was significantly increased after BMA injection of orexin-A (P<0.05). After administration of orexin-A into the BMA, food intake of the normal rats, DIO rats and DR rats ((2.38±0.34) g, (3.75±0.32) g, (4.01±0.38) g, respectively) was significantly increased (P<0.01), and the food intake of DR and DIO rats were significantly higher than that of normal rats (P<0.05). After BMA was injected with naloxone, the food intake of rats was inhibited, and the food intake of the DIO rats was significantly lower than that of the DR rats (P<0.05), food intake of the DR rats was significantly lower than that of the normal rats (P<0.05). The results of real-time PCR showed that the mRNA levels of OX-1R in DIO and DR rats were( 5.85±0.45 )and (6.03±0.42) were higher than that of normal rats, and the difference was significant (P<0.05); and mRNA levels of μ-opioid receptors in DIO and DR rats((4.51±0.42) and (8.31±0.41)times) were higher than those in normal rats (P<0.05). The results of Elisa showed that the protein levels of OX-1R in DIO ((2.98±0.28) ng/μl) and DR rats ((3.05±0.31) ng/μl) were higher than those in normal rats ((1.53±0.31)ng/μl, P<0.05). The content of μ-opioid receptor protein in DR rats ((4.21±0.35)ng/μl) was higher than that of DIO rats ((2.77±0.27) ng/μl), and higher than that of normal rats((1.48±0.32) ng/μl), the difference was significant (P<0.05). Conclusion BMA orexin-A promotes the spontaneous discharge of GD-sensitive neurons and food intake in normal rats, DIO rats and DR rats, μ-opioid receptors may be involved in the regulation of this process. Key words: Orexin-A; Food intake; Gastric distension-sensitive neurons; Diet-induced obesity rat; Amygdala

Clinical Therapeutic Effect of Naloxone Combined with Hemodialysis on Acute Severe Alcoholism.

BackgroundThe aim of this research was to investigate the treatment effect of naloxone combined with hemodialysis on acute severe alcoholism.Material/MethodsWe included 36 patients treated with naloxone combined with hemodialysis in Group I and 34 patients treated with naloxone without hemodialysis in Group II. The Glasgow coma scale (GCS) score, the consciousness recovery time, alanine amino transferase (ALT) level, and complications were analyzed.ResultsMean GCS score in Group I was higher than that in Group II, with a significant difference (P<0.05). The consciousness recovery time in Groups I and II were 3.0±0.8 h and 6.9±2.1 h, respectively, with a significant difference (P<0.05). After naloxone treatment and hemodialysis, the ALT level in Group I was lower than that in Group II (P<0.05). Moreover, the incidence of hepatic and renal function damages in Group I was smaller than that in Group II (P<0.05). Only 1 patient in Group I developed pneumonia, which was fewer than that in Group II, with a significant difference (P<0.05).ConclusionsNaloxone combined with hemodialysis effectively reduces the central inhibition of alcohol, shortens consciousness recovery time, improves respiratory and cardiovascular function, decreases hepatic and renal function damages, and reduces the incidence of complications.

Fentanyl and naloxone effects on glutamate and GABA release rates from anterior hypothalamus in freely moving rats

Fentanyl, a μ-opioid receptor agonist, has been studied for its neuro/psycho-pharmacological effects since its first clinical use; however, its effect on the release rate of the Central Nervous System (CNS) neurotransmitters has not been yet elucidated. In the present study the influence of fentanyl on the release rates of glutamate and GABA is investigated. Specifically, we examined the effects of intravenous (10 μg/kg) as well as intrahypothalamic (0.1nmol/min) fentanyl administration on the release rates of GABA and glutamate in the superfusate of anterior hypothalamus, under tail pinch manipulation. The release rate of the neurotransmitters was monitored by the push–pull superfusion technique. To investigate the role of fentanyl the opioid antagonist, naloxone 0.1 mg/kg was administered intravenously, or 50nmol/min intrahypothalamicaly. The amino acids were determined by High Performance Liquid Chromatography (HPLC) and fluorimetric detection after NBD-Cl derivatisation. After intravenous fentanyl administration a significant decrease of glutamate and increase of GABA release rates were observed. However during the pain manipulations, the release rate of glutamate was increased. Intravenous naloxone did not affect significantly the release rates of both amino acids, while intrahypothalamic antagonist administration reversed the alterations in both neurotransmitters release rates. Our results demonstrate that there is an opioid-glutamatergic transmission pathway, located in hypothalamus and that opioids can activate NMDA receptors, thus reducing the nociceptive threshold and the opioid analgesic effect.

Naloxone Effectiveness: A Systematic Review.

Naloxone Effectiveness: A Systematic Review.

Naloxone attenuates ischemic brain injury in rats through suppressing the NIK/IKKα/NF-κB and neuronal apoptotic pathways.

Although naloxone has been documented to exert neuroprotection in animal model of cerebral ischemia, the mechanism is not well understood. In this present study we investigated whether naloxone affected the mitochondrial apoptotic pathway in ischemic brain injury of rats. SD rats were subjected to a permanent middle cerebral artery occlusion surgery, and received naloxone (0.5, 1, 2 mg/kg, i.v.) immediately after ischemia. Neurological deficits were evaluated 24 h after ischemia using the McGraw Stroke Index, and then the rats were killed, and the brains were collected for further analyses. We show that naloxone treatment dose-dependently decreased the infarction volume and morphological injury, improved motor behavioral function, and markedly curtailed brain edema. Furthermore, naloxone administration significantly inhibited the nuclear translocation of NF-κB p65 and decreased the levels of nuclear NF-κB p65 in the ischemic penumbra. Naloxone administration also dose-dependently increased the NF-κB inhibitory protein (IκBα) levels and attenuated phosphorylated NIK and IKKα levels in the ischemic penumbra. In addition, naloxone administration dose-dependently increased Bcl-2 levels, decreased Bax levels, stabilized the mitochondrial transmembrane potential, and inhibited cytochrome c release and caspase 3 and caspase 9 activation. These results indicate that the neuroprotective effects of naloxone against ischemic brain injury involve the inhibition of NF-κB activation via the suppression of the NIK/IKKα/IκBα pathway and the obstruction of the mitochondrial apoptotic pathway in neurons.

Bladder underactivity after prolonged stimulation of somatic afferent axons in the tibial nerve in cats.

To establish an animal model of bladder underactivity induced by prolonged and intense stimulation of somatic afferent axons in the tibial nerve. In seven cats under α-chloralose anesthesia, tibial nerve stimulation (TNS) of 30-min duration was repeatedly (3-8 times) applied at 4-6 times threshold (T) intensity for inducing a toe twitch to produce bladder underactivity determined by cystometry. Naloxone (1 mg/kg, i.v.) was administered to examine the role of opioid receptors in TNS-induced bladder underactivity. After prolonged (1.5-4 h) and intense (4-6T) TNS, a complete suppression of the micturition reflex occurred in six cats and an increase in bladder capacity to about 150% of control and a decrease in the micturition contraction amplitude to 50% of control occurred in one cat. The bladder underactivity was maintained for at least 1-1.5 h. Naloxone reversed the bladder underactivity, but an additional 30-min TNS removed the naloxone effect. The results indicate that prolonged and intense activation of somatic afferent axons in the tibial nerve can suppress the central reflex mechanisms controlling micturition. This animal model may be useful for examining the pathophysiology of neurogenic bladder underactivity and for development of new treatments for underactive bladder symptoms.

Effects of naloxone on opioid receptors in spinal cord dorsal horn of neuropathic pain rat models

Objective To investigate the effects of naloxone on the levels of opioid receptors in spinal cord dorsal horn of neuropathic pain rat models, established with chronic constriction injury(CCI). Methods Male SD rats (200-250 g) were subjected to CCI to establish neuropathic pain models. The rats were divided into 4 groups, and respectively received sham operation and saline treatment (Sham-S group, n=8), CCI and saline treatment (CCI-S group, n=8), CCI and naloxone treatment (CCI-N group, n=24), and CCI and morphine treatment (CCI-M group, n=8). Drug treatments (subcutaneous injection of normal saline, 10 mg·kg-1·d-1 naloxone, or 10 mg·kg-1·d-1 morphine in hindpaw) started from 7th day after surgery for 8 consecutive days. Paw withdrawal mechanical threshold (PWMT) and paw withdrawalthermal latency(PWTL) respectively were measured with von Frey tests and thermal plantar tests before and after CCI. Spinal cord dorsal horn at L3-L5 levels from naloxone-treated CCI rats were collected 10, 12, and 14 days after surgery, and western blot assay was employed to measure the levels of three opioid receptor subtypes. Results CCI rats exhibited ipsilateral hindpaw hyperalgesia, showing reduced PWMT and shortened PWTL (P 0.05) . Conclusions Naloxone, an opioid receptor antagonist, showed antinociceptive effects, similar to morphine, an opioid receptor agonist, on CCI neuropathic pain. This effect probably is relevant to naloxone-induced elevation of DOR in spinal cord dorsal horn. Key words: Naloxone; Neuropathic pain; Opioid receptors

Simulation of the Effects of Co-Locating Naloxone with Automated External Defibrillators

Introduction: Opioid-related overdoses have been steadily increasing over the past decade in the United States. Naloxone is used by first responders to revive overdose victims, but results may be improved by increasing access to and usage of naloxone by bystanders. Automated External Defibrillators (AEDs) are pervasive, recognizable, and publicly accessible. Co-locating naloxone kits with AEDs could increase public naloxone access and usage. However, the impact of co-locating naloxone kits with AEDs is not known. Objectives: We sought to evaluate the impact of co-locating naloxone kits with AEDs in a simulation study centered on Allegheny County, Pennsylvania. Methods: Naloxone administration frequency (N = 3,650) at the zip-code level from March 2016 to March 2017 was provided by the Allegheny County Health Department. AED point locations (N = 1,653) were obtained from the University of Pittsburgh's Resuscitation Logistics and Informatics Venture. Zip-code level geospatial analyses were conducted using QGIS and STATA to determine the correlation between AED count and naloxone administrations. AED naloxone kit (N-AED) coverage, based on a maximum “walking-distance” radius of 200 m, was estimated at a zip-code level using the QGIS buffer tool and a custom MATLAB script. Potential impact of N-AEDs was estimated assuming uniform spatial distribution of naloxone administrations. Results: The median (IQR) AED coverage based on a 200 m access radius per zip code was 4% (0–7). The median (IQR) number of naloxone administrations per zip code was 27(7-55). A total of 82 zip codes had data for both AED locations and naloxone administrations. The correlation between number of AEDs and naloxone administrations per zip code was 0.20. Overall, 16% of naloxone administrations were estimated to be covered by an N-AED. Conclusion: Using these limited methods, co-locating naloxone with AEDs is not likely to have a standalone impact on preventing overdose fatalities.

Does training people to administer take-home naloxone increase their knowledge? Evidence from Australian programs.

Take-home naloxone (THN) programs have been operating in Australia since 2012 in a variety of settings. We examine whether THN programs were effective in increasing knowledge about opioid overdose and appropriate responses in program participants. Data were obtained from pre- and post-training questionnaires administered as part of the early evaluations of THN naloxone programs operated in Sydney (n = 67), Melbourne (n = 280), Perth (n = 153) and Canberra (n = 183). Pooled data from comparable items, analysed in the domains specified in previously-developed evaluation scales, were compared using repeated-measures analysis of variance and random effects logistic regression. Results pre- and post-training were compared as well as results across sites. High levels of knowledge about overdose risks and signs and appropriate actions to take were observed at baseline and this generally improved over time. No substantial differences were identified across cities. Knowledge also increased with participant age but the improvements over time were similar in each age group. There were small differences by participant gender with knowledge generally higher among females. THN programs are effective in improving knowledge related to overdose response. Major improvements in knowledge were limited to overdose recognition and effect of naloxone suggesting that education may best be focused on overdose signs and the use of naloxone among populations accessed through these programs. A focus on younger people also appears warranted. Further work is needed to understand the impact of training and knowledge on actual behaviours around overdose events.

Polymethoxyflavones from Nicotiana plumbaginifolia (Solanaceae) Exert Antinociceptive and Neuropharmacological Effects in Mice.

Polymethoxylavones (PMFs) are known to exhibit significant anti-inflammatory and neuroprotective properties. Nicotiana plumbaginifolia, an annual Bangladeshi herb, is rich in polymethoxyflavones that possess significant analgesic and anxiolytic activities. The present study aimed to determine the antinociceptive and neuropharmacological activities of polyoxygenated flavonoids namely- 3,3′,5,6,7,8-hexamethoxy-4′,5′-methylenedioxyflavone (1), 3,3′,4′,5′,5,6,7,8-octamethoxyflavone (exoticin) (2), 6,7,4′,5′-dimethylenedioxy-3,5,3′-trimethoxyflavone (3), and 3,3′,4′,5,5′,8-hexamethoxy-6,7-methylenedioxyflavone (4), isolated and identified from N. plumbaginifolia. Antinociceptive activity was assessed using the acetic-acid induced writhing, hot plate, tail immersion, formalin and carrageenan-induced paw edema tests, whereas neuropharmacological effects were evaluated in the hole cross, open field and elevated plus maze test. Oral treatment of compounds 1, 3, and 4 (12.5–25 mg/kg b.w.) exhibited dose-dependent and significant (p < 0.01) antinociceptive activity in the acetic-acid, formalin, carrageenan, and thermal (hot plate)-induced pain models. The association of ATP-sensitive K+ channel and opioid systems in their antinociceptive effect was obvious from the antagonist effect of glibenclamide and naloxone, respectively. These findings suggested central and peripheral antinociceptive activities of the compounds. Compound 1, 3, and 4 (12.5 mg/kg b.w.) demonstrated significant (p < 0.05) anxiolytic-like activity in the elevated plus-maze test, while the involvement of GABAA receptor in the action of compound 3 and 4 was evident from the reversal effects of flumazenil. In addition, compounds 1 and 4 (12.5–25 mg/kg b.w) exhibited anxiolytic activity without altering the locomotor responses. The present study suggested that the polymethoxyflavones (1–4) from N. Plumbaginifolia could be considered as suitable candidates for the development of analgesic and anxiolytic agents.