The Potential Risk of Reduced Serum Cholinesterase Activity in COVID-19 Patients Suffering From Cytokine Storm.

Background and objective Several blood biochemical parameters are used to biomonitor coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Reduced serum cholinesterase (ChE) has been suggested to be a predictive indicator of the severity and outcome of COVID-19 infection. This study aimed to examine serum ChE activity in hospitalized and terminally ill COVID-19 patients with cytokine storm and evaluate the enzyme for the in vitro ChE-inhibitory activity of the organophosphate dichlorvos. Methods We determined the serum ChE activity, electrometrically, among hospitalized COVID-19-cytokine storm patients and their non-cytokine storm counterparts. Aliquots of serum samples from healthy volunteers, COVID-19-cytokine storm patients, and non-cytokine storm COVID-19 patients were pooled separately. They were incubated in vitro for 10 minutes with dichlorvos at 0.25 or 0.5 µM. Serum samples from the three groups were subjected to ChE inhibition temporally (5-60 minutes) by 0.25 µM dichlorvos to evaluate the kinetics of enzyme inhibition using steady-state kinetics. Results Of the 165 hospitalized patients with COVID-19, 33 (20%) suffered from the cytokine storm. Serum ChE activity of female COVID-19 patients with cytokine storm was significantly lower than that of the non-cytokine storm counterparts. Risk analysis of reduced serum ChE activity (≥20%) among the 33 COVID-19 patients with cytokine storm compared to 111 non-cytokine storm COVID-19 patients revealed that the former were significantly at risk of reduced enzyme activity. In vitro, dichlorvos at 0.25 µM and 0.5 µM significantly inhibited serum ChE activity in all the groups. The COVID-19-cytokine storm group was the least affected. Dichlorvos at 0.25 µM progressively (5-60 minutes) inhibited serum ChE activity. The inhibition kinetic parameters in COVID-19-cytokine storm patients showed a decrease in the half-life of inhibition (14.54%), inhibition rate (51.46%), and total inhibition time (14.55%). Conclusions Reduced serum ChE in COVID-19 patients with cytokine storm could be adopted as a potential additional laboratory examination tool for bedside risk assessment. The in vitro inhibition profile of serum ChE activity by dichlorvos in COVID-19-cytokine storm patients suggests reduced susceptibility of the enzyme to inhibition. The response of COVID-19 patients to ChE-inhibiting medications should be cautiously evaluated with prior in vitro tests.

Antidotal Effects of the Antihistamine Diphenhydramine Against Cholinesterase Inhibitor Poisoning: A Meta-Analysis of Median Lethal Doses in Experimental Animals.

The H1-antihistamine diphenhydramine antagonizes cholinesterase inhibitor poisoning in various animal species. One aspect of acute antidotal actions of diphenhydramine is increasing the median lethal doses (LD50) of toxicants. The objective of this meta-analysis was to assess the antidotal action of diphenhydramine against short-term toxicity (LD50) of cholinesterase inhibitors in experimental animals. The experimental studies selected were according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. They were conducted in laboratory animals (mice, rats, and chicks) to determine acute LD50 values of cholinesterase inhibitors (organophosphates, carbamates, and imidocarb) under the influence of diphenhydramine vs. controls. Twenty-eight records were selected from 12 studies on mice (n= 242), rats (n= 27), and young chicks (n= 128). The forest plot of randomized two-group meta-analysis assessed effect size, subgroup analysis, drapery prediction, heterogeneity, publication bias-funnel plot as well as one-group proportions meta-analysis of percent protection. Diphenhydramine significantly increased the combined effect size (i.e. increased LD50) in intoxicated experimental animals in comparison to controls (-3.71, standard error (SE) 0.36, 95%CI -4.46, -2.97). The drapery plot proposed a wide range of confidence intervals. The I2 index of heterogeneity of the combined effect size was high at 81.03% (Q= 142.3, p < 0.0001). Galbraith regression also indicated data heterogeneity; however, the normal quantile plot indicated no outliers. Subgroup analysis indicated significantly high heterogeneity with organophosphates (I2 = 63.72%) and carbamates (I2 = 76.41%), but low with imidocarb (I2 = 51.48%). The funnel plot and Egger regression test (t= -13.7, p < 0.0001) revealed publication bias. The median of the diphenhydramine protection ratio was 1.655, and the related forest plot of one group proportion meta-analysis revealed a statistically high level of protection (0.594, SE 0.083, 95%CI 0.432, 0.756), with high heterogeneity (I2= 99.86). The risk of bias assessment was unclear, while the total score (16 out of 20) of each study leaned towards the side of the low risk of bias. In conclusion, the meta-analysis of LD50 values indicated that diphenhydramine unequivocally protected experimental animals from the acute toxicity of cholinesterase inhibitors. The drug could be an additional antidote against acute poisoning induced by cholinesterase inhibitors, but a word of caution: it is not to be considered as a replacement for the standard antidote atropine sulfate. Further studies are needed to examine the action of diphenhydramine on adverse chronic effects of cholinesterase inhibitors.

Oxidative Stress-Induced Adverse Effects of Three Statins Following Single or Repetitive Treatments in Mice.

Background and objective The hypolipidemic statins have been associated with various side effects, and in some cases, adverse reactions in humans and experimental animals, such as myotoxicity, neurobehavioral toxicity, as well as liver and kidney injuries. The purpose of the present study was to examine the possibility of the induction of oxidative stress in the brain and plasma of mice dosed with single or repetitive doses of three statins (atorvastatin, simvastatin, and rosuvastatin). Methods Male Swiss-origin mice were dosed orally with single doses of each of the three statins at 500 or 1000 mg/kg of body weight. Other groups of mice were dosed orally with repeated daily doses of each of the statins at 200 mg/kg of body weight/day for 14 or 28 consecutive days. These doses of statins were chosen to not produce overt toxicity in mice within the time frame allocated for each experiment. Brain and plasma glutathione (GSH) and malondialdehyde (MDA) levels, as well as liver enzymes activities alanine transaminase (ALT) and aspartate transaminase (AST), were determined using commercial kits. Results Single-dose treatments of the mice with the statins at either 500 or 1000 mg/kg significantly and dose-dependently (p < 0.05) reduced the GSH level in the plasma and the whole brain when compared with respective control values. Atorvastatin was the least effective statin, as only the high dose achieved a significant reduction in brain GSH level in comparison with the respective control value. Repetitive administration of the three statins at 200 mg/kg of body weight/day for 14 or 28 consecutive days significantly and time-dependently reduced plasma and brain GSH levels in comparison with respective control values. The oxidative stress biomarker MDA level significantly increased in the plasma and brain of mice following single or repetitive treatments with the three statins, and the most effective one was rosuvastatin. In association with these changes, activities of the liver enzymes ALT and AST were also increased in the plasma with single and repetitive statin treatments, and the most effective one was rosuvastatin. Conclusion The data suggest an association of high doses of three statins (atorvastatin, simvastatin, and rosuvastatin) with the induction of oxidative stress manifested as GSH reduction and MDA elevation as adverse effects in the brain and plasma of mice, which suffered from the additional burden of liver injury. These effects could be the basis of an in-depth exploration of statin adverse effects in experimental animals and to find an animal model, probably the mice, for the induction of adverse effects of statins that target the brain, as well as to shed light on potential statin intolerance outcomes following single-dose treatments in this species.

Polypharmacy and the In Silico Prediction of Potential Body Proteins Targeted by These Drugs Among Hospitalized COVID-19 Patients With Cytokine Storm.

Background and objective Polypharmacy is prevalent in coronavirus disease 2019 (COVID-19) patients with severe disease. However, information on polypharmacy among COVID-19 patients who also suffer from cytokine storm is scarce. In light of this, the purpose of the present study was to assess the incidence of polypharmacy and in silico prediction of potential body proteins targeted by these drugs among hospitalized COVID-19 patients who were identified to have the additional burden of cytokine storm in the city of Duhok, Kurdistan Region, Iraq. Methods This was a cross-sectional observational study conducted from June 2021 to April 2022; the phenomena of major polypharmacy (six to nine medications) and excessive polypharmacy (≥10 medications) were documented among 33 (15 males and 18 females) COVID-19 patients with cytokine storm during their hospital stay (8-45 days) in Duhok, Kurdistan Region, Iraq. The SwissTargetPrediction program was utilized in silico to predict and identify human body proteins that could be potentially targeted by selected medications involved in polypharmacy. Results All patients had tested positive for COVID-19 via PCR testing, and they showed different signs and symptoms of the disease. None of the patients recovered and all of them deceased. All 33 patients received many therapeutic agents that ranged in number from eight to 20/patient during their hospital stay. The mean number of medications was 15 ± 3. We identified 2/33 (6%) patients with major polypharmacy (eight and nine) and 31/33 (94%) with excessive polypharmacy (15.5 ± 2.7). The total number of medications identified in polypharmacy was 37, excluding vitamins, minerals, and intravenous solutions. The frequency of medications administered was as follows: antibiotics (67, 13.7%), mucolytic agents (56, 11.5%), corticosteroids (54, 11%), anticoagulants (48, 9.8%), antiviral agents (41, 8.4%), antihypertensive agents (32, 6.5%), analgesics (28, 5.7%), antifungal drugs (27, 5.5%), antidiabetics (26, 5.3%), and other medications (2-19, 0.41-3.9%). Using the SwissTargetPrediction program, various drugs including antiviral agents involved in polypharmacy were found to target, in silico, body proteins at a prediction percentage that ranged from 6.7% to 40%. Conclusions Major and extensive polypharmacy conditions were identified in hospitalized COVID-19 patients suffering from cytokine storm. The severity of COVID-19 with cytokine storm, comorbidities, and hospitalization were key factors associated with polypharmacy in the patients. The SwissTargetPrediction web server is useful for predicting in silico potential human body protein targets that could possibly be sources of additional information on the adverse/toxic effects of polypharmacy medications administered concurrently. Further research in current medication protocols prescribed for advanced COVID-19 illness with cytokine storm is warranted to gain deeper insights into the topic.

Association of Reduced Maternal Plasma Cholinesterase Activity With Preeclampsia: A Meta-Analysis.

Blood butyrylcholinesterase (BChE) activity has been found to decrease during pregnancy and reportedly decrease even more in preeclampsia (PE). The purpose of the present meta-analysis was to answer a specific question of whether BChE activity (in the plasma, serum, or whole blood) is reduced in pregnant women suffering from PE compared to those with normal pregnancy. The meta-analysis included 15 studies with 20 records of BChE activity in 608 women compared to 569 healthy pregnant (control) ones. The studies were subjected to quality assessment using the Newcastle-Ottawa Scale (NOS). Using the Meta-Essentials software program 1.5, the one-group random effects model and forest plot revealed that the percentage of BChE activity in pregnant women with PE was 84.84% of the control value, with a standard error of 4.09 and 95% C.I. of 76.28, 93.41, indicating a significant 15.16% reduction in BChE activity in comparison to healthy pregnancy. No significant heterogeneity was seen in the analyzed data and the funnel plot did show publication bias. Subgroup (mild, severe, and unclassified PE) forest plot analysis revealed that the % BChE activities in PE compared to respective healthy pregnancies were 96.28%, 97.08%, and 76.62%, respectively with no heterogeneity. The median NOS score of the 15 studies included in the meta-analysis was 7, ranging from 5 to 8 (medium to high quality), and the forest plot showed an effect size of 0.735. This meta-analysis shows that BChE activity is reduced in PE compared with normal pregnancy and its value as a biomarker warrants further clinical studies.

First meta-analysis study of cholinesterase inhibition in experimental animals by organophosphate or carbamate insecticides under the influence of diphenhydramine.

Background and Aim: Diphenhydramine is an H1-antihistamine that counteracts the toxic effects of organophosphate and carbamate insecticides that inhibit cholinesterase (ChE) activity. This meta-analysis aimed to investigate the effects of diphenhydramine on ChE inhibition induced by these insecticides in the plasma, erythrocytes, or whole brain of experimental animals. Materials and Methods: A data search was performed on erythrocyte, plasma, and brain ChE inhibition caused by organophosphate and carbamate insecticides in experimental animals (mice, rats, and chicks) treated with the antihistamine diphenhydramine in accordance with preferred reporting items for systematic reviews and meta-analysis, which was done by the two-group random-effects model meta-analysis. The meta-analysis included 18 records extracted from six studies that, appeared from 1996 to 2022. Results: Using the random-effects model, a two-group meta-analysis revealed that the combined effect size (ChE inhibition) was significantly more favorable in the control group than in the diphenhydramine intervention, as shown by a forest plot. The combined effect size (standardized mean difference) was 0.67, with a standard error of 0.3, a lower limit of 0.04, and an upper limit of 1.29 (p = 0.025). The heterogeneity was moderate, as I2 of the combined effect size was 74%, with a significant Cochrane Q-test result (Q = 65, p < 0.0001). Subgroup analysis indicated that, with brain ChE inhibition, the heterogeneity (I2) became 5%, which was lower than ChE inhibition in plasma (84%) and erythrocytes (78%). No publication bias was identified using the funnel plot and Egger's test. Conclusion: This meta-analysis suggests that, in addition to its documented antidotal action against ChE-inhibiting insecticides, diphenhydramine can also reduce the extent of ChE inhibition, especially in the brain, which is the main site of toxicity of these insecticides. There is a need for additional studies to assess such enzyme inhibition in different parts of the brain.

Plasma Cholinesterase Activity in Patients With Rheumatoid Arthritis and Toxoplasmosis.

Background and objective Rheumatoid arthritis (RA) is a chronic autoimmune disease causing synovium inflammation and functional impairment. Toxoplasmosis is an intracellular zoonotic parasitic infection and a risk factor in immunosuppressed diseases including RA. The involvement of the cholinergic mechanism is not clear when both diseases exist in combination. This study aimed to examine plasma cholinesterase (ChE) activity in patients suffering from RA with concomitant toxoplasmosis, taking into account the enzyme susceptibility to in vitro inhibitory challenge with the organophosphate dichlorvos in RA patients. Methods This was a case-control study involving 88 RA patients and 61 healthy controls of both genders. The RA patients were allocated into three groups. The first group received no therapy (n=14), the second group received conventional anti-arthritis therapy (n=49), and the third group received conventional + biologic therapy (n=25). Plasma ChE activity was determined by an electrometric method. Plasma samples were screened for Toxoplasma gondii (T. gondii) infection, using ELISA T. gondii antibodies IgG and IgM. In vitro inhibition of plasma ChE activity was assessed by incubating the samples with dichlorvos at 0.25 and 0.5 µM. The time-dependent dichlorvos (0.25 µM)-induced plasma ChE inhibition and its kinetics were determined. Results The RA patients comprised 76 (86.4%) females and 12 males (13.6%), whereas healthy controls included 22 (36.1%) females and 39 (63.9%) males. The rates of toxoplasmosis IgG positivity in controls and RA patients were 26.2% and 39.8%, respectively. Plasma ChE activity in patients with RA was significantly higher than that in the control group, by 16%. Plasma ChE values of RA patients with conventional therapy and conventional + biologic therapy were higher than that of the control group, by 18% and 27%, respectively. Odds and risk ratios of elevated plasma ChE activity (20%) in RA patients with therapy indicated that high plasma ChE activity among RA patients with therapy is a risk factor. The plasma ChE activity of T. gondii IgG-positive RA patients was not significantly different from that of the IgG-negative ones. Dichlorvos at 0.25 and 0.5 µM significantly inhibited in vitro plasma ChE activity in controls and RA patients. The rates of plasma ChE inhibition by dichlorvos were lower in the RA groups with conventional therapy in comparison with those in the control group (77% vs. 91%). Examining the dichlorvos time-dependent ChE inhibition kinetics, RA groups showed increases in the half-life of inhibition by 23.6% to 32.7% and the total inhibition time by 23.5% to 32.5%, together with decreases in the inhibition rate constant by 19% to 24.5%, an indication of reduced inhibition rate of plasma ChE activity compared to that of the control group. Conclusions The autoimmune nature of RA and its chronicity might have contributed to the increase in plasma ChE activity among the patients. This increase in enzyme activity could be a risk factor in RA patients undergoing conventional therapy alone or in combination with biologic therapy; however, the clinical significance of such a condition remains obscure at present. The in vitro inhibition of plasma ChE activity in RA patients suggests reduced susceptibility of the enzyme to ChE inhibition by dichlorvos. Toxoplasmosis was not a risk factor when plasma ChE activity was taken into account among RA patients.

Effects of acute manganese neurotoxicity in young chicks.

Manganese (Mn) is an industrial neurotoxicant in humans and animal models limited to rodent species. The present study analyses the potential neurotoxicity of acute Mn administration in young chicks. The acute (24 h) LD50 values of Mn following intraperitoneal, intramuscular, subcutaneous and oral administrations of MnCl2 in seven-day-old chicks were 21.3 mg kg-1, 28.1 mg kg-1, 28.1 mg kg-1 and 469.5 mg kg-1 body weight of Mn, respectively. Signs of Mn poisoning appeared in the chicks within 2 min and 13 min after parenteral administration and within 20 min and 32 min after oral administration. The signs demonstrated the depressant action of Mn in the chicks. The behavioural effects of Mn given at 5 mg kg-1, 10 mg kg-1 and 20 mg kg-1 intramuscularly were examined in 7 to 12 day old chicks using the three-minute open-field and tonic immobility tests. Manganese decreased the overall locomotor activity of the chicks in the open-field arena as manifested by a significant increase in the latency to move from the central square and decreases in line crossing, frequency of defecation and vocalization score when compared to control values. It also increased the duration of the chicks' tonic immobility response. Pharmacological challenges of Mn-treated chicks with general anaesthetics xylazine-ketamine and thiopental caused the loss of right reflex at a faster rate in comparison with control values. Thiopental increased the duration of loss of righting reflex in Mn-treated chicks when compared with that of the control group. Chlorpromazine challenge of Mn-treated chicks significantly increased the depressant action of Mn in the open-field arena and increased the duration of tonic immobility response produced by the metal. The injections of Mn at 10 mg kg-1, 20 mg kg-1, 50 mg kg-1 and 100 mg kg-1 intramuscularly significantly increased the Mn levels in the plasma, liver, kidneys and entire brain of the chicks. The data suggests acute neurotoxicity of Mn chloride in the young chicks as a form of depressant action that could be determined by open-field and tonic immobility tests with further support from pharmacological challenges.

Antinociception by metoclopramide, ketamine and their combinations in mice.

BACKGROUND: Metoclopramide is a centrally acting antiemetic and ketamine is a general anesthetic used with sedatives, tranquilizers and analgesics. Metoclopramide has analgesic effects and its combination with ketamine causes sedation and hypnosis. The contribution of metoclopramide to the analgesic effect of ketamine is not known. The purpose of the present study was to explore the analgesic effects of metoclopramide and ketamine alone or in combination in mice. METHODS: The up-and-down method was used to determine the median effective analgesic dosages (ED(50)s) of metoclopramide and ketamine administered intraperitoneally (ip) either alone or concomitantly in male albino Swiss mice. Analgesia was measured by using a hot plate. The ED(50)s of both drugs were analyzed isobolographically to determine the type of interaction between them. The analgesic effect of metoclopramide-ketamine combination (62.3 and 4.3 mg/kg, ip) was also monitored by the hot plate and acetic acid writhing methods. RESULTS: The analgesic ED(50)s for metoclopramide and ketamine in mice were 30.15 and 2.15 mg/kg, ip, respectively. Concomitant administration of the drugs reduced their ED(50)s to 10.17 and 0.68 mg/kg, ip, respectively. Isobolographic analysis of these ED(50)s for both drugs revealed synergistic analgesic effect. Further, the combination of the drugs was effective analgesic as seen by the hot plate test and by another analgesic test paradigm, the acetic acid-induced writhings in mice. CONCLUSIONS: The data suggest that the combination of metoclopramide and ketamine synergistically controls acute pain in mice. This combination could be used clinically for restraint and minor surgical interventions in mice.

Developmental and behavioral effects of medetomidine following in ovo injection in chicks.

Developmental and behavioral effects of medetomidine were assessed in chicks following in ovo exposure on incubation day 4. Medetomidine at 25 and 50 µg/egg injected once into the air cell on incubation day 4, dose-dependently decreased the number of viable chick embryos starting on day 10 of the incubation. The percentages of successful hatching in the control and medetomidine treated groups were 93, 60 and 47%, respectively. Embryo lethalities in these groups were 7, 40 and 53%, respectively. In ovo exposure of the chicks to medetomidine at 25 and 50 µg/egg did not significantly affect the body weight of the chicks as well as their morphometric measurements. In another experiment, 3- and 8-day old chicks exposed to medetomidine in ovo (25 µg/egg) were monitored in the open-field for 5 min. Medetomidine suppressed the open-field activity of both 3- and 8-day old chicks. This was manifested by a significant increase in the latency to move from the central square of the open-field arena and a decrease in the number of lines crossed (ambulation) with an additional decrease in vocalizations of the 3-day old chicks when compared with respective age-matched control values. In the same medetomidine-exposed chicks the duration of tonic immobility significantly increased in comparison with respective control values. Pharmacological challenge of the medetomidine-exposed chicks (8-day old) with medetomidine at 25 µg/kg, intramuscularly significantly increased the latencies to onset of sedation and loss of righting reflex and decreased the duration of sleep when compared with the saline-control group challenged in the same manner. The data suggest that medetomidine could be a behavioral teratogen in chicks following in ovo exposure.

Effects of hydrogen peroxide on diazepam and xylazine sedation in chicks.

Oxidative stress may cause various neuronal dysfunctions and modulate responses to many centrally acting drugs. This study examines the effects of oxidative stress produced by hydrogen peroxide (H2O2) on sedation induced by diazepam or xylazine as assessed in 7-14 day-old chicks. Day-old chicks were provided with either plane tap water (control group) or H2O2 in tap water as 0.5% v/v drinking solution for two weeks in order to produce oxidative stress. Spectrophotometric methods were used to determine glutathione and malondialdehyde concentrations in plasma and whole brain. Drug-induced sedation in the chicks was assessed by monitoring the occurrence of signs of sedation manifested as drooping of the head, closed eyelids, reduced motility or immotility, decreased distress calls, and recumbency. The latency to onset of sedation and its duration were also recorded. H2O2 treatment for two weeks significantly decreased glutathione and increased malondialdehyde concentrations in plasma and whole brain of the chicks on days 7, 10 and 14 as compared with respective age-matched control groups. H2O2 decreased the median effective doses of diazepam and xylazine for the induction of sedation in chicks by 46% and 63%, respectively. Injection of diazepam at 2.5, 5 and 10 mg/kg, i.m. or xylazine at 2, 4 and 8 mg/kg, i.m. induced sedation in both control and H2O2-treated chicks in a dose dependent manner, manifested by the above given signs of sedation. H2O2 significantly decreased the latency to onset of sedation in chicks treated with diazepam at 5 and 10 mg/kg, increased the duration of sedation and prolonged the total recovery time in comparison with respective non-stressed control chicks. A similar trend occurred with xylazine in the H2O2-treated chicks, though the differences from control counterparts did not attain the statistical significance, except for the recovery time of the lowest dose of the drug. The data suggest that H2O2-induced oxidative stress sensitizes the chicks to the depressant action of the sedatives diazepam and xylazine. Further studies are needed to examine the potential role of oxidative stress in modulating the actions of therapeutic agents on the brain.

Acute toxicity of veterinary and agricultural formulations of organophosphates dichlorvos and diazinon in chicks.

Formulation components of organophosphate insecticidal preparations might affect their toxic action in animals. The objective of this study was to examine and compare the acute toxicity and cholinesterase inhibition in seven to 14-day-old chicks dosed orally with dichlorvos and diazinon in standard veterinary and agricultural formulations. The acute (24 h) oral median lethal doses (LD50) of the formulations were determined using the up-and-down method. Respective LD50 of dichlorvos of the veterinary and agricultural formulations in chicks were 11.1 mg kg(-1) and 6.51 mg kg(-1) and those of diazinon 6.4 mg kg(-1) and 6.7 mg kg(-1). Plasma and brain cholinesterase activities were measured by electrometry after in vivo and in vitro exposure to organophosphates. The chicks showed signs of cholinergic toxicosis within one hour of dosing. Dichlorvos (8 mg kg(-1)) and diazinon (4 mg kg(-1)) in the veterinary and agricultural formulation significantly reduced both plasma and brain cholinesterase activities in the chicks. The veterinary formulation of dichlorvos reduced plasma ChE by 60% and agricultural by 40% and brain ChE by 93% and 87%, respectively. In contrast, ChE inhibition by diazinon in the agricultural formulation of diazinon was stronger than by the veterinary formulation; 72% vs. 64% in plasma and 97% vs. 80% in the brain, respectively. The highest in vitro inhibitions were observed with dichlorvos in the agricultural formulation (50%) in the brain samples and with diazinon in the agricultural formulation (52%) in the plasma samples. While they exist, differences between formulations cannot be taken as a rule and further investigations should inventory the toxicity of standard veterinary and agricultural organophosphate formulations in addition to the known data for pure forms.

Plasma and whole brain cholinesterase activities in three wild bird species in Mosul, IRAQ: In vitro inhibition by insecticides.

Plasma and brain cholinesterase activities were determined in three wild bird species to assess their exposure to organophosphate and carbamate insecticides which are used in agriculture and public health. In the present study, we used an electrometric method for measurement of cholinesterase activities in the plasma and whole brain of three indigenous wild birds commonly found in northern Iraq. The birds used were apparently healthy adults of both sexes (8 birds/species, comprising 3-5 from each sex) of quail (Coturnix coturnix), collard dove (Streptopelia decaocto) and rock dove (Columba livia gaddi), which were captured in Mosul, Iraq. The mean respective cholinesterase activities (Δ pH/30 minutes) in the plasma and whole brain of the birds were as follows: quail (0.96 and 0.29), collard dove (0.97and 0.82) and rock dove (1.44 and 1.42). We examined the potential susceptibility of the plasma or whole brain cholinesterases to inhibition by selected insecticides. The technique of in vitro cholinesterase inhibition for 10 minutes by the organophosphate insecticides dichlorvos, malathion and monocrotophos (0.5 and 1.0 µM) and the carbamate insecticide carbaryl (5 and10 µM) in the enzyme reaction mixtures showed significant inhibition of plasma and whole brain cholinesterase activities to various extents. The data further support and add to the reported cholinesterase activities determined electrometrically in wild birds in northern Iraq. The plasma and whole brain cholinesterases of the birds are highly susceptible to inhibition by organophosphate and carbamate insecticides as determined by the described electrometric method, and the results further suggest the usefulness of the method in biomonitoring wild bird cholinesterases.

Acute toxicity and cholinesterase inhibition in chicks dosed orally with organophosphate insecticides.

Acute toxic effects of three commonly used insecticidal preparations of the organophosphates chlorpyrifos, diazinon, and dichlorvos were examined in mixed breed broiler chicks, and cholinesterase activity in plasma and brain were measured. The acute (24 h) oral median lethal doses (LD50) of chlorpyrifos, diazinon, and dichlorvos were 10.79 mg kg(-1), 6.32 mg kg(-1), and 6.30 mg kg(-1), respectively, as determined by the up-and-down method in chicks. Signs of cholinergic toxicosis in the chicks appeared within two hours after dosing, and they included salivation, lacrimation, gasping, frequent defecation, drooping of wings, tremors, convulsions, and recumbency before death. Halving the oral LD50 of chlorpyrifos (5 mg kg(-1)), diazinon (3 mg kg(-1)), and dichlorvos (3 mg kg(-1)) caused immobility and wing drooping, but not the clinical signs of cholinergic toxicity. However, at full LD50 doses of these insecticides, chicks showed clinical signs of cholinergic toxicity similar to those seen in the LD50 experiments. Two out of six chicks died within two hours after treatment with LD50 doses of chlorpyrifos and dichlorvos, whereas LD50 dosing with diazinon caused death in three out of six chicks. Compared to control values, the insecticides reduced plasma and whole brain cholinesterase activities by 29% to 84% and 18% to 77%, respectively, depending on the dose. The decrease in plasma cholinesterase correlated well (r=0.82) with that of the brain. These data suggest that organophosphate insecticides administered orally at LD50 doses induce clinical signs of cholinergic poisoning and concurrently reduce brain and plasma cholinesterase activities in chicks.

Sedative and hypnotic effects of combined administration of metoclopramide and ketamine in chickens.

Metoclopramide is a dopamine receptor antagonist used in animals as both an antiemetic and a gastroprokinetic agent. In chickens, the drug causes central nervous system depression. The authors examined the potential sedative and hypnotic effects of metoclopramide when administered in combination with the anesthetic agent ketamine in 1-3-week-old chicks. Concomitant administration of metoclopramide and ketamine markedly reduced the median effective doses (ED50s) of both drugs for the induction of sedation and sleep in the chicks. The results suggest potential therapeutic applications of the metoclopramide-ketamine combination as a restraining agent in avian species not intended for human consumption.

Metoclopramide-induced central nervous system depression in the chicken.

BACKGROUND: Metoclopramide is a dopamine D2-receptor antagonist used as an antiemetic and gastroprokinetic agent in man and animals. The drug causes sedation as a side effect in man. Such a sedative action of metoclopramide has not been documented in the chicken as the drug is not used clinically in this species. The present study examines the central nervous system depressant effects of metoclopramide in 7-14 days old broiler chicks. RESULTS: Injection of metoclopramide at 50, 100 and 200 mg/kg, subcutaneously (s.c.) induced sedation in the chicks in a dose dependent manner. The chicks manifested, within 3.6-19 minutes of metoclopramide injection, signs of sedation characterized by drooping of the head and wings, closed eyelids, reduced motility and decreased distress calls. The duration of sedation ranged between 37.2 to 163.4 minutes. Metoclopramide at 100 and 200 mg/kg induced, within 12.2 and 6.2 minutes, sleep (loss of righting reflex) for 43.8 and 158.6 minutes, respectively. The median effective doses of metoclopramide for induction of sedation and sleep in the chicks were 11 and 53 mg/kg, s.c., respectively. Lower doses of metoclopramide (5 and 10 mg/kg, s.c.) significantly decreased the open-field activity of the chicks and increased the durations of their tonic immobility. All treated-chicks recovered from the central nervous system depressant effect of metoclopramide without any observable adverse effects. CONCLUSION: The data suggest that metoclopramide induces central nervous system depression in chicks, and the drug could have potential clinical applications as a sedative-hypnotic agent in avian species not intended for human consumptions.