Pentobarbital Withdrawal Research Articles

Pentobarbital withdrawal and treatment in an infant in the pediatric cardiac intensive care unit

Withdrawal syndromes following administration of sedative and analgesic infusions represent a significant morbidity that is described increasingly in the pediatric critical care literature. However, there are few descriptions of pentobarbital withdrawal symptoms and their treatment in the pediatric population. We describe an infant receiving multiple sedative and analgesic medications, including pentobarbital, who was resistant to our institution's standard weaning protocol, but whose severe withdrawal symptoms responded dramatically to phenobarbital loading and maintenance.

Pentobarbital withdrawal

Pentobarbital withdrawal

Hashimoto Encephalopathy Causing Drug-Resistant Status Epilepticus Treated With Plasmapheresis

Hashimoto encephalopathy is a rare, clinically heterogenous condition. Its treatment is based on corticosteroids. A previously normal 12-year-old boy was admitted to our pediatric emergency department with status epilepticus. He experienced a recurrence of status epilepticus after pentobarbital withdrawal, and required repeated resumptions of drug-induced coma. He manifested acute personality changes. His limbic encephalitis markers were normal, but his level of anti-thyroid peroxidase antibody was high. A diagnosis of Hashimoto encephalopathy was considered. Our patient responded to plasmapheresis instead of corticosteroid treatment. This case report is the first, to the best of our knowledge, of plasmapheresis because of Hashimoto encephalopathy in a child.

Characterisation of pentobarbital physical dependence and withdrawal in rats

Characterisation of pentobarbital physical dependence and withdrawal in rats

Pentobarbital withdrawal

Pentobarbital withdrawal

Fine mapping of a sedative‐hypnotic drug withdrawal locus on mouse chromosome 11

We have established that there is a considerable amount of common genetic influence on physiological dependence and associated withdrawal from sedative-hypnotic drugs including alcohol, benzodiazepines, barbiturates and inhalants. We previously mapped two loci responsible for 12 and 9% of the genetic variance in acute alcohol and pentobarbital withdrawal convulsion liability in mice, respectively, to an approximately 28-cM interval of proximal chromosome 11. Here, we narrow the position of these two loci to a 3-cM interval (8.8 Mb, containing 34 known and predicted genes) using haplotype analysis. These include genes encoding four subunits of the GABA(A) receptor, which is implicated as a pivotal component in sedative-hypnotic dependence and withdrawal. We report that the DBA/2J mouse strain, which exhibits severe withdrawal from sedative-hypnotic drugs, encodes a unique GABA(A) receptor gamma2 subunit variant compared with other standard inbred strains including the genetically similar DBA/1J strain. We also demonstrate that withdrawal from zolpidem, a benzodiazepine receptor agonist selective for alpha1 subunit containing GABA(A) receptors, is influenced by a chromosome 11 locus, suggesting that the same locus (gene) influences risk of alcohol, benzodiazepine and barbiturate withdrawal. Our results, together with recent knockout studies, point to the GABA(A) receptor gamma2 subunit gene (Gabrg2) as a promising candidate gene to underlie phenotypic differences in sedative-hypnotic physiological dependence and associated withdrawal episodes.

Selection for pentobarbital withdrawal severity: correlated differences in withdrawal from other sedative drugs

In mice, withdrawal from agents that depress central nervous system function, such as barbiturates and benzodiazepines, results in the production of a withdrawal syndrome, one feature of which is increased severity of handling induced convulsions (HICs). High and Low Pentobarbital Withdrawal mice (HPW and LPW) were selectively bred to display severe and mild pentobarbital withdrawal HICs, respectively. These mice provide a valuable means to assess genetic correlations between withdrawal from pentobarbital and other sedative agents. We tested HPW and LPW mice for severity of HICs elicited during withdrawal from ethanol, diazepam, and zolpidem, and measured consumption of and preference for pentobarbital solutions in HPW and LPW mice. HPW mice displayed greater HICs than LPW mice during ethanol and zolpidem withdrawal, but differed less robustly during diazepam withdrawal. LPW mice consumed more pentobarbital in a solution of a moderate concentration than did HPW mice, but did not consume more pentobarbital at a higher or lower concentration. These results indicate that some of the same genes that affect the severity of withdrawal from pentobarbital also influence ethanol and zolpidem withdrawal, but that diazepam withdrawal may be less influenced by these genes.

Potential pleiotropic effects of Mpdz on vulnerability to seizures.

We previously mapped quantitative trait loci (QTL) responsible for approximately 26% of the genetic variance in acute alcohol and barbiturate (i.e., pentobarbital) withdrawal convulsion liability to a < 1 cM (1.8 Mb) interval of mouse chromosome 4. To date, Mpdz, which encodes the multiple PSD95/DLG/ZO-1 (PDZ) domain protein (MPDZ), is the only gene within the interval shown to have allelic variants that differ in coding sequence and/or expression, making it a strong candidate gene for the QTL. Previous work indicates that Mpdz haplotypes in standard mouse strains encode distinct protein variants (MPDZ1-3), and that MPDZ status is genetically correlated with severity of withdrawal from alcohol and pentobarbital. Here, we report that MPDZ status cosegregates with withdrawal convulsion severity in lines of mice selectively bred for phenotypic differences in severity of acute withdrawal from alcohol [i.e., High Alcohol Withdrawal (HAW) and Low Alcohol Withdrawal (LAW) lines] or pentobarbital [High Pentobarbital Withdrawal (HPW) and Low Pentobarbital Withdrawal (LPW) lines]. These analyses confirm that MPDZ status is associated with severity of alcohol and pentobarbital withdrawal convulsions. Using a panel of standard inbred strains of mice, we assessed the association between MPDZ status with seizures induced by nine chemiconvulsants. Our results show that MPDZ status is genetically correlated with seizure sensitivity to pentylenetetrazol, kainate and other chemiconvulsants. Our results provide evidence that Mpdz may have pleiotropic effects on multiple seizure phenotypes, including seizures associated with withdrawal from two classes of central nervous system (CNS) depressants and sensitivity to specific chemiconvulsants that affect glutaminergic and GABAergic neurotransmission.

Congenic Mapping of Alcohol and Pentobarbital Withdrawal Liability Loci to a &lt;1 Centimorgan Interval of Murine Chromosome 4: Identification ofMpdzas a Candidate Gene

Risk for onset of alcoholism is related to genetic differences in acute alcohol withdrawal liability. We previously mapped a locus responsible for 26% of the genetic variance in acute alcohol withdrawal convulsion liability to a >35 centimorgan (cM) interval of murine chromosome 4. Here, we narrow the position of this locus to a <1 cM interval (approximately 1.8 megabase, containing 15 genes and/or predicted genes) using a combination of novel, interval-specific congenic strains and recombinant progeny testing. We report the development of a small-donor-segment congenic strain, which confirms capture of a gene affecting alcohol withdrawal within the <1 cM interval. We also confirm a pentobarbital withdrawal locus within this interval, suggesting that the same gene may influence predisposition to physiological dependence on alcohol and a barbiturate. This congenic strain will be invaluable for determining whether this interval also harbors a gene(s) underlying other quantitative trait loci mapped to chromosome 4, including loci affecting voluntary alcohol consumption, alcohol-induced ataxia, physical dependence after chronic alcohol exposure, and seizure response to pentylenetetrazol or an audiogenic stimulus. To date, Mpdz, which encodes the multiple PSD95/DLG/ZO-1 (PDZ) domain protein (MPDZ), is the only gene within the interval shown to have allelic variants that differ in coding sequence and/or expression. Sequence analysis of 15 standard inbred mouse strains identifies six Mpdz haplotypes that predict three MPDZ protein variants. These analyses, and evidence using interval-specific congenic lines, show that alcohol withdrawal severity is genetically correlated with MPDZ status, indicating that MPDZ variants may influence alcohol withdrawal liability.

Changes of the level of G protein alpha-subunit mRNA by tolerance to and withdrawal from pentobarbital in rats.

Pentobarbital was continuously infused intracerebroventricularly (i.c.v.) at the rate of 300 micrograms/10 microliters/h for 7 days, and withdrawal from pentobarbital was rendered 24 h after the stopping of the infusion. To eliminate the induction of hepatic metabolism by systemic administration of pentobarbital, an i.c.v. infusion model of tolerance to and withdrawal from pentobarbital was used. Little is known about the functional modulation of the G protein alpha-subunits at the molecular level. The effects of continuous infusion of pentobarbital on the modulation of G protein alpha-subunits mRNA were investigated by using in situ hybridization study. In situ hybridization showed that the level of G alpha s mRNA was increased in the septum and brainstem, and the level of G alpha o mRNA was elevated in the cortex during the pentobarbital withdrawal. The level of G alpha i mRNA was significantly elevated in almost all area of brain during the pentobarbital withdrawal. These results suggest that region-specific changes of G protein alpha-subunit mRNA were involved in the withdrawal from pentobarbital, whereas alpha-subunit is not so highly involved in the pentobarbital tolerance.

Preclinical abuse potential assessment of the anticonvulsant zonisamide

AbstractZonisamide (Zonegran®) is a broad‐spectrum antiepileptic agent that shares some pharmacological properties with other anticonvulsants, including phenytoin, carbamazepine, and valproic acid, but is differentiated from these agents by the ability to significantly block T‐type calcium channels. Zonisamide interacts with the γ‐amino‐butyric acid (GABA) receptor in an allosteric manner, and thus does not modulate GABA receptor effects. However, given the potential of drugs within the latter class for drug abuse in humans, an evaluation of zonisamide for abuse potential is an important component of its potential side‐effect profile. In the present study, zonisamide was tested in animal models of the subjective and reinforcing effects of central nervous system (CNS) depressant drugs, e.g., diazepam discrimination in rats and intravenous self‐administration in rhesus monkeys, respectively. In addition, zonisamide was evaluated for physical dependence liability in a chronic infusion model using rats. Zonisamide did not substitute for diazepam in rats trained to discriminate 2.5‐mg/kg diazepam from vehicle nor was it self‐administered by rhesus monkeys experienced in methohexital‐reinforced responding. Continuous infusion of zonisamide (400 or 600 mg/kg/day) did not prevent the loss of body weight associated with discontinued pentobarbital infusion. These doses of zonisamide did produce some incomplete attenuation of observable signs of pentobarbital withdrawal, likely due to direct sedative or depressant effects of these high doses. These results suggest that zonisamide would not produce diazepam‐like intoxication in humans nor would it likely be subject to abuse when made more widely available. Further, when administered chronically, zonisamide would not be expected to produce physical dependence of the CNS depressant type. Taken together, these results support the prediction that zonisamide would have low abuse liability. Drug Dev. Res. 54:66–74, 2001. © 2001 Wiley‐Liss, Inc.

Genomewide search for epistasis in a complex trait: pentobarbital withdrawal convulsions in mice.

The well-documented difference in pentobarbital withdrawal severity between DBA/2J and C57BL/6J mice offers the opportunity to study how differences between allelic variants influence pentobarbital withdrawal via their additive and/or dominance effects and to identify modifier loci that also influence the trait via gene-gene interactions (a form of epistasis). Previous work in our laboratory identified seven provisional quantitative trait loci (QTLs) for pentobarbital withdrawal using BXD recombinant inbred strains. To date, only one of these QTLs has been confirmed, Pbw1. We hypothesized that other loci that act epistatically may also influence genetic variance in pentobarbital withdrawal severity. Using Epistat, a program developed to carry out full-genome searches for epistasis, we identified six provisional epistatic interactions (p < .002) between the provisional QTLs and modifier loci elsewhere in the genome. Verification testing of these interactions using 404 B6D2F2 mice provided supporting evidence that a QTL on chromosome 11 contributes to genetic variance in pentobarbital withdrawal, but only in the presence of a modifier allele on distal chromosome 1 (p = .0004). This modifier is in the same genomic vicinity as loci detected for a variety of withdrawal and seizure phenotypes.

Genetic factors in addiction: QTL mapping and candidate gene studies implicate GABAergic genes in alcohol and barbiturate withdrawal in mice.

Quantitative trait locus (QTL) mapping has allowed dramatic progress toward the detection and chromosome mapping of minor and major gene loci involved in murine responses to alcohol and other drugs of abuse. Here we focus on the identification of QTLs for one particular trait relevant to addiction, drug withdrawal following acute or chronic drug administration. To date, five significant QTLs (p < 5 x 10(-5)) and six suggestive QTLs (p < 0.001) have been mapped to specific murine chromosomes for alcohol and pentobarbital withdrawal, indicating the presence of a relevant gene or genes at each location. Overlapping QTLs for alcohol withdrawal and pentobarbital withdrawal are identified on murine chromosomes 1, 4, and 11, and may detect the influence of common genes. For many QTLs, candidate genes with relevant neurobiological function lie within the mapped region. Notably, several QTLs for alcohol and pentobarbital withdrawal are in proximity to genes that directly or indirectly affect GABAA receptor-mediated transmission, which has been implicated in some of the actions of alcohol and other drugs. These include a cluster of GABAA receptor genes and genes encoding the enzymes steroid 5 alpha-reductase-1 (involved in biosynthesis of the neuroactive steroid allopregnanolone) and glutamic acid decarboxylase-1 (involved in GABA biosynthesis). This paper will discuss data that examines the involvement of GABAergic genes in withdrawal and other drug responses, including genetic variation in gene sequence, expression and function.

N-Methyl-D-aspartate receptor NR1 subunit mRNA level was decreased in rat brain during pentobarbital withdrawal.

We examined the effect of continuous intracerebroventricular (i.c.v. ) administration of pentobarbital on the level of N-Methyl-D-aspartate receptor NR1 subunit mRNAs in different regions of rat brain by in situ hybridization histochemistry. Animals were rendered tolerant to pentobarbital by continuous i.c.v. infusion (300 microgram/10 microliter/h for 6 days) through pre-implanted cannulae connected to osmotic mini-pumps, and dependent, by abrupt withdrawal from pentobarbital. NR1 subunit mRNA level was significantly decreased in the entorhinal cortex, cingulate, caudate-putamen, septum, and the CA1 of hippocampus in pentobarbital withdrawal rats. The level of NR1 mRNAs was decreased in only CA1 of hippocampus in pentobarbital tolerant rats. These results indicate that withdrawal from i.c.v. infusion with pentobarbital decreases in NR1 subunit expression in the rat brain, suggesting that changes in expression of NR1 subunit may contribute to the development of withdrawal from pentobarbital.

Genetic Determinants of Severity of Acute Withdrawal From Diazepam in Mice: Commonality With Ethanol and Pentobarbital

Potentially life-threatening seizures can occur following withdrawal from benzodiazepines, ethanol, or barbiturates. In animals, withdrawal severity has been shown to be partially genetically determined for each drug class. Susceptibility to these drugs is partially determined by common genetic factors, but the evidence is conflicting. We tested the hypothesis that acute benzodiazepine withdrawal convulsions are influenced by at least some genes that also affect withdrawal from ethanol and pentobarbital. Results in inbred mouse strains demonstrate that strain susceptibility is genetically correlated with susceptibility to ethanol and pentobarbital. The proportion of variance accounted for by genetic factors common to diazepam and ethanol was estimated at 69%. Results contrast with previous data obtained in mice that were serially tested for withdrawal severity from ethanol, pentobarbital, and then diazepam, because serial testing of mice significantly affected the previous results for some strains. Diazepam withdrawal severity was also genetically correlated with pentobarbital withdrawal. Together, these results suggest that some genes influence severity of withdrawal from several types of depressant drugs.

Quantitative trait loci affecting risk for pentobarbital withdrawal map near alcohol withdrawal loci on mouse chromosomes 1, 4, and 11.

Barbiturate dependence is associated with the development of physiological dependence (withdrawal), tolerance, or a maladaptive pattern of drug use. Analysis of strain and individual differences with animal models for physiological dependence liability are useful means to identify potential genetic determinants of liability in humans. Behavioral and quantitative trait locus (QTL) mapping analyses were conducted with mice that are resistant versus sensitive to pentobarbital withdrawal. With a multistage genetic mapping strategy, a pentobarbital withdrawal QTL (Pbw1) was mapped to the distal region of mouse Chromosome (Chr) 1 and may be identical to an alcohol withdrawal QTL mapped to this chromosomal region. Two suggestive QTLs for pentobarbital withdrawal, both in proximity to QTLs definitely mapped for alcohol withdrawal, were also tentatively identified. These were on Chr 11 in proximity to a gene cluster including several members of the GABAA receptor gene family, and on Chr 4 near a locus associated with beta-carboline-induced seizure severity. These data represent the first detection and mapping of loci influencing risk for physiological dependence on barbiturates, and suggest the involvement of common genes in physiological dependence on pentobarbital and alcohol.

Changes of [3H]muscimol binding and GABA(A) receptor beta2-subunit mRNA level by tolerance to and withdrawal from pentobarbital in rats.

Effects of continuous pentobarbital administration on binding characteristics of [3H]muscimol were examined by autoradiography, and levels of GABA(A) receptor beta2-subunit mRNA were investigated by in situ hybridization histochemistry in the rat brain. In order to eliminate the induction of hepatic metabolism by systemic administration of pentobarbital, an i.c.v. infusion model of tolerance to and withdrawal from pentobarbital was used. An experimental model of barbiturate tolerance and withdrawal was developed using i.c.v. infusion of pentobarbital (300 microg/10 microl/hr for 7 days) by osmotic minipumps and abrupt withdrawal from pentobarbital. The levels of [3H]muscimol binding were elevated in cingulate of frontal cortex (46%) and granule layer of cerebellum (32%) of rats 24-hr after withdrawal from pentobarbital, while it was only elevated in cingulate (58%) of tolerant rats. The GABA(A) receptor beta2-subunit mRNA was increased in the withdrawal rats only: in the cortex (9-14%), hippocampus (15-21%), inferior colliculus (21%), and granule layer of cerebellum (24%). These results show the involvement of GABA(A) receptor and its beta2-subunit up-regulations in pentobarbital withdrawal rats, and suggest that the levels of [3H]muscimol binding and GABA(A) receptor beta2-subunit mRNA are altered in a region-specific manner during pentobarbital withdrawal.

Autoradiography of [ 3H]glutamate binding during pentobarbital tolerance and withdrawal in the rat

The influence of centrally administered pentobarbital on [ 3H]glutamate receptor binding in the rat brain was examined. Animals were rendered tolerant by intracerebroventricular (i.c.v.) infusion through osmotic minipumps with pentobarbital (300 μg/10 μl/h, for 6 days), and dependent, by 24 h after withdrawal from pentobarbital. Pentobarbital tolerant rats have significant increases in [ 3H]glutamate binding in the cortex and hippocampus area. Pentobarbital withdrawal produced increases in glutamate binding in many regions, e.g., the cortex, hippocampus area, thalamus, and cerebellum. These results show that chronic i.c.v. infusion with pentobarbital increases N-methyl- d-aspartate (NMDA) displaceable [ 3H]glutamate binding, suggesting that an increase in NMDA binding sites may play an important role in the development of tolerance to and withdrawal from pentobarbital.

Changes in [3H]forskolin binding to adenylate cyclase and [3H]phorbol dibutyrate binding to protein kinase C in pentobarbital tolerant/dependent rats.

These studies were designed to examine the effect of chronic administration of pentobarbital on activity of adenylate cyclase (AC) and protein kinase C (PKC) in the rat brain by autoradiography. Recently, it has been suggested that the phosphorylation of specific proteins may be involved in the development of physical dependence. An experimental model of barbiturate tolerance and dependence was developed using i.c.v. infusion of pentobarbital (300 microg/10 microl/hr for 7 days) by osmotic minipumps and abrupt withdrawal from pentobarbital. The levels of [3H]forskolin binding were elevated (28-67%) in cortex, thalamus, dentate gyrus, hippocampal CA3 and cerebellum of the pentobarbital withdrawal animals, while these changes were not observed in tolerant rats. The levels of [3H]phorbol dibutyrate binding were highly elevated (38-65%) in the region of cortex, caudate putamen, septum, thalamus, dentate gyrus, and cerebellum of rats withdrawal from pentobarbital. These results show that the levels of AC and PKC were significantly elevated in pentobarbital withdrawal rats, and suggest that the levels of AC and PKC are altered in a region-specific manner during pentobarbital withdrawal.

Changes in NMDAR2 subunit mRNA levels during pentobarbital tolerance/withdrawal in the rat brain: an in situ hybridization study.

Little is known about the functional modulation of NMDA receptor subunits at the molecular level. Therefore, a series of experiments were conducted to elucidate more fully the role of NMDA receptor subtypes in pentobarbital tolerance and withdrawal. We investigated the influence of centrally administered pentobarbital on the regulation of mRNA levels of the family of NMDA receptor 2 (NR2) subtypes (NR2A, NR2B, and NR2C) by in situ hybridization histochemistry in rat brain. Animals were rendered tolerant by continuous intracerebroventricular (i.c.v.) infusion with pentobarbital (300 microg/10 microl/hr for 6 days) through pre-implanted cannulae connected to osmotic mini-pumps, and dependent, by abrupt withdrawal from pentobarbital. The NR2A subunit mRNA was increased in cortical areas in pentobarbital tolerant and withdrawal rats. In contrast, the NR2B mRNA was decreased in parietal cortex and hippocampus in both tolerance and withdrawal rats. The level of NR2C mRNA was increased in withdrawal rats, while there was no change in tolerant rats. These results indicate that continuous i.c.v. infusion with pentobarbital alters NR2 subunit mRNA expression in the rat brain, suggesting that NR2 subunits may play an important role in the development of tolerance to and withdrawal from pentobarbital.