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Purpose: Previous quantitative trait loci (QTL) mapping studies from our laboratory identified a 6.6 Mb segment of distal chromosome 1 that contains a gene (or genes) having a strong influence on the difference in seizure susceptibility between C57BL/6 (B6) and DBA/2 (D2) mice. A gene transfer strategy involving a bacterial artificial chromosome (BAC) DNA construct that contains several candidate genes from the critical interval was used to test the hypothesis that a strain-specific variation in one (or more) of the genes is responsible for the QTL effect., Methods: Fertilized oocytes from a seizure-sensitive congenic strain (B6.D2-Mtv7a/Ty-27d) were injected with BAC DNA and three independent founder lines of BAC-transgenic mice were generated. Seizure susceptibility was quantified by measuring maximal electroshock seizure threshold (MEST) in transgenic mice and nontransgenic littermates., Results: Seizure testing documented significant MEST elevation in all three transgenic lines compared to littermate controls. Allele-specific RT-PCR analysis confirmed gene transcription from genome-integrated BAC DNA and copy-number-dependent phenotypic effects were observed., Conclusions: Results of this study suggest that the gene(s) responsible for the major chromosome 1 seizure QTL is found on BAC RPCI23-157J4 and demonstrate the utility of in vivo gene transfer for studying quantitative trait genes in mice. Further characterization of this transgenic model will provide new insight into mechanisms of seizure susceptibility.

Background: The mouse C57BL/6 (C57) and DBA/2J (DBA) inbred strains differ substantially in many aspects of their response to drugs of abuse. The development of microarray analyses represents a genome-wide method for measuring differences across strains, focusing on expression differences. In the current study, we carried out microarray analysis in C57 and DBA mice in the nucleus accumbens of drug-naïve and morphine-treated animals., Results: We identified mRNAs with altered expression between the two strains. We validated the mRNA expression changes of several such mRNAs, including Gnb1, which has been observed to be regulated by several drugs of abuse. In addition, we validated alterations in the enzyme activity of one mRNA product, catechol-O-methyltransferase (Comt). Data mining of expression and behavioral data indicates that both Gnb1 and Comt expression correlate with aspects of drug response in C57/DBA recombinant inbred strains. Pathway analysis was carried out to identify pathways showing significant alterations as a result of treatment and/or due to strain differences. These analyses identified axon guidance genes, particularly the semaphorins, as showing altered expression in the presence of morphine, and plasticity genes as showing altered expression across strains. Pathway analysis of genes showing strain by treatment interaction suggest that the phosphatidylinositol signaling pathway may represent an important difference between the strains as related to morphine exposure., Conclusion: mRNAs with differing expression between the two strains could potentially contribute to strain-specific responses to drugs of abuse. One such mRNA is Comt and we hypothesize that altered expression of Comt may represent a potential mechanism for regulating the effect of, and response to, multiple substances of abuse. Similarly, a role for Gnb1 in responses to multiple drugs of abuse is supported by expression data from our study and from other studies. Finally, the data support a role for semaphorin signaling in morphine effects, and indicate that altered expression of genes involved in phosphatidylinositol signaling and plasticity might also affect the altered drug responses in the two strains.

Many studies have shown that acupuncture can contribute to the biochemical balance in the central nervous system and maintenance or recovery of homeostasis. It is well known that chronic administration of ethanol may produce depletion or sensitization of extracellular dopamine levels in the nucleus accumbens. The present study was designed to investigate the effects of acupuncture on chronic ethanol-induced changes in extracellular dopamine levels in the nucleus accumbens shell (using in vivo microdialysis in unanesthetized rats). Male Sprague-Dawley rats were treated with 3 g/kg/day of ethanol (20%, w/v) or saline by intraperitoneal injection for 21 days. Following 72 h of ethanol withdrawal, acupuncture was applied at bilateral Shenmen (HT7) points for 1 min. Different group of rats using the same paradigm of ethanol treatment were acupunctured at the same points after the systemic ethanol challenge (3 g/kg, i.p.). Acupuncture at the specific acupoint HT7, but not at control points (PC6 or tail) significantly prevented both a decrease of extracellular dopamine levels in the nucleus accumbens during ethanol withdrawal and an increase in accumbal dopamine levels induced by the ethanol challenge. These results provided strong evidence that stimulation of the specific acupoint HT7 helps to normalize the release of dopamine in the mesolimbic system following chronic ethanol treatment.

Acupuncture as a therapeutic intervention has been used for the treatment of many functional disorders including substance abuse. However, there are still many unanswered question about the basic mechanism underlying acupuncture's effectiveness in the treatment of drug addiction. Repeated injection of psycostimulants or morphine can produce behavioral and neurochemical sensitization and have been used as a model for studying drug addiction. The present study was designed to investigate the effect of acupuncture on repeated morphine-induced changes in extracellular dopamine levels using in vivo microdialysis and repeated morphine-induced behavioral changes. Male Sprague-Dawley rats were treated with saline or increasing doses of morphine (10, 20 and 40 mg/kg, s.c., twice daily for 3 days). Following 15 days of withdrawal, acupuncture was applied at bilateral Shenmen (HT7) points for 1 min after the systemic challenge with morphine HCl (5 mg/kg, s.c.). Results showed that acupuncture at the specific acupoint HT7, but not at control points (TE8 and tail) significantly decreased both dopamine release in the nucleus accumbens and behavioral hyperactivity induced by a systemic morphine challenge. These results suggest that the therapeutic effect of acupuncture on morphine addiction occurs through inhibition of neurochemical and behavioral sensitization to morphine.

C57BL/6 (B6) and DBA/2 (D2) mice exhibit disparate behavior when tested for voluntary morphine intake in a two-bottle choice drinking paradigm with B6 mice consuming 10 times more drug than D2 mice. Previous genetic mapping studies identified a locus, Mop2, on the proximal part of chromosome 10 that explained over half of the genetic variance in this mouse model of opioid self-administration. We constructed a set of reciprocal congenic strains between B6 and D2 mice in which the proximal portion of chromosome 10 has been introgressed from one strain onto the background of the other. We tested mice from this pair of reciprocal strains together with progenitor B6 and D2 mice in a two-bottle choice drinking paradigm with morphine and quinine. The results showed that introgression of chromosome 10 alleles from the B6 strain onto a D2 genetic background increased voluntary morphine intake four-fold compared to progenitor D2 mice. Preference for morphine was also increased significantly in D2.B6-Mop2 mice compared to progenitor D2 mice. Conversely, introgression of chromosome 10 alleles from the D2 strain onto a B6 genetic background decreased morphine intake by half compared to progenitor B6 mice in B6.D2 -Mop2 mice; however, high morphine preference was maintained in this congenic strain most likely due to strong quinine aversion. When quinine was eliminated from the control bottle, morphine preference in B6.D2-Mop2 mice was decreased significantly relative to B6 and D2.B6-Mop2 mice. Overall, these data confirm the existence of a gene(s) on chromosome 10 proximal to D10Mit124 that has a strong influence on the difference in morphine drinking behavior between B6 and D2 mice.

Clinical trials are currently underway to determine the effectiveness of acupuncture in the treatment of drug abuse. However, there are still many unanswered questions about the basic mechanisms of acupuncture. Studies have shown that the GABA(B) receptor system may play a significant modulatory role in the mesolimbic system in drug abuse, including ethanol. The in vivo microdialysis study was designed to investigate the effect of acupuncture on acute ethanol-induced dopamine release in the nucleus accumbens and the potential role of the GABA(B) receptor system in acupuncture. Male Sprague-Dawley rats were administered with the highly selective GABA(B) antagonist SCH 50911 (3 mg/kg, i.p.) 1h prior to an intraperitoneal injection of ethanol (1 g/kg). Immediately after ethanol treatment, acupuncture was given at bilateral Shenmen (HT7) points for 1min. Acupuncture at the specific acupoint HT7, but not at control points (PC6 or tail) significantly decreased dopamine release in the nucleus accumbens. Inhibition of dopamine release by acupuncture was completely prevented by SCH 50911. These results suggest that stimulation of specific acupoints inhibits ethanol-induced dopamine release by modulating GABA(B) activity and imply that acupuncture may be effective in blocking the reinforcing effects of ethanol.

Previous quantitative trait loci (QTL) mapping studies document that the distal region of mouse Chromosome (Chr) 1 contains a gene(s) that is in large part responsible for the difference in seizure susceptibility between C57BL/6 (B6) (relatively seizure-resistant) and DBA/2 (D2) (relatively seizure-sensitive) mice. We now confirm this seizure-related QTL ( Szs1) using reciprocal, interval-specific congenic strains and map it to a 6.6-Mb segment between Pbx1 and D1Mit150. Haplotype conservation between strains within this segment suggests that Szs1 may be localized more precisely to a 4.1-Mb critical interval between Fcgr3 and D1Mit150. We compared the coding region sequences of candidate genes between B6 and D2 mice using RT-PCR, amplification from genomic DNA, and database searching and discovered 12 brain-expressed genes with SNPs that predict a protein amino acid variation. Of these, the most compelling seizure susceptibility candidate is Kcnj10. A survey of the Kcnj10 SNP among other inbred mouse strains revealed a significant effect on seizure sensitivity such that most strains possessing a haplotype containing the B6 variant of Kcnj10 have higher seizure thresholds than those strains possessing the D2 variant. The unique role of inward-rectifying potassium ion channels in membrane physiology coupled with previous strong association between ion channel gene mutations and seizure phenotypes puts even greater focus on Kcnj10 in the present model. In summary, we confirmed a seizure-related QTL of large effect on mouse Chr 1 and mapped it to a finely delimited region. The critical interval contains several candidate genes, one of which, Kcnj10, exhibits a potentially important polymorphism with regard to fundamental aspects of seizure susceptibility.

Purpose: Our research program uses genetic linkage and association analysis to identify human seizure sensitivity and resistance alleles. Quantitative trait loci mapping in mice led to identification of genetic variation in the potassium ion channel gene Kcnj10, implicating it as a putative seizure susceptibility gene. The purpose of this work was to translate these animal model data to a human genetic association study., Methods: We used single stranded conformation polymorphism (SSCP) electrophoresis, DNA sequencing and database searching (NCBI) to identify variation in the human KCNJ10 gene. Restriction fragment length polymorphism (RFLP) analysis, SSCP and Pyrosequencing were used to genotype a single nucleotide polymorphism (SNP, dbSNP rs#1130183) in KCNJ10 in epilepsy patients (n = 407) and unrelated controls (n = 284). The epilepsy group was comprised of patients with refractory mesial temporal lobe epilepsy (n = 153), childhood absence (n = 84), juvenile myoclonic (n = 111) and idiopathic generalized epilepsy not otherwise specified (IGE-NOS, n = 59) and all were of European ancestry., Results: SNP rs#1130183 (C > T) alters amino acid 271 (of 379) from an arginine to a cysteine (R271C). The C allele (Arg) is common with conversion to the T allele (Cys) occurring twice as often in controls compared to epilepsy patients. Contingency analysis documented a statistically significant association between seizure resistance and allele frequency, Mantel-Haenszel chi square = 5.65, d.f. = 1, P = 0.017, odds ratio 0.52, 95% CI 0.33-0.82., Conclusion: The T allele of SNP rs#1130183 is associated with seizure resistance when common forms of focal and generalized epilepsy are analyzed as a group. These data suggest that this missense variation in KCNJ10 (or a nearby variation) is related to general seizure susceptibility in humans.

Inhibition of mitochondrial respiratory chain function may contribute to dopaminergic neurodegeneration in the substantia nigra (SN) of patients with Parkinson disease (PD). Since large-scale structural changes (e.g. deletions and rearrangements in mitochondrial DNA [mtDNA]) have been associated with mitochondrial dysfunction, we tested the hypothesis that increased total mtDNA deletions/rearrangements are associated with neurodegeneration in PD. This study employed a well-established technique, long-extension polymerase chain reaction (LX-PCR), to detect the multiple mtDNA deletions/rearrangements in the SN of patients with PD, multiple system atrophy (MSA), dementia with Lewy bodies (DLB), Alzheimer disease (AD), and age-matched controls. We also compared the total mtDNA deletions/rearrangements in different brain regions of PD patients. The results demonstrated that both the number and variety of mtDNA deletions/rearrangements were selectively increased in the SN of PD patients compared to patients with other movement disorders as well as patients with AD and age-matched controls. In addition, increased mtDNA deletions/rearrangements were observed in other brain regions in PD patients, indicating that mitochondrial dysfunction is not just limited to the SN of PD patients. These data suggest that accumulation of total mtDNA deletions/rearrangements is a relatively specific characteristic of PD and may be one of the contributing factors leading to mitochondrial dysfunction and neurodegeneration in PD.

Forced immobilization is a simple and effective stressor which produces large increases in heart rate (HR), blood pressure (BP), and plasma levels of norepinephrine (NE) and epinephrine (EPI). This study investigated the effects of electroacupuncture on BP, HR, and plasma catecholamine levels in rats challenged with immobilization stress. Male Sprague-Dawley rats received electroacupuncture (3 Hz, 0.2 ms pulses, 20 mA) for 30 min after start of immobilization stress (180 min). Needlepoints corresponded to Shaohai (HT3) and Neiguan (PC6) on the heart and pericardium channel. BP and HR were monitored with an indwelling carotid catheter, and blood samples were taken from the jugular vein. Blood (for HPLC determination of NE and EPI), mean BP, and HR were sampled at rest and during the immobilization stress at 15, 30, 60, 90, 120, 150, and 180 min. Electroacupuncture at HT3 and PC6 points but not at control points (TE5, LI11, and tail) significantly reduced the expected increases in BP, HR, and attenuated plasma levels of NE and EPI in response to 3 h of immobilization stress. Results provide strong evidence that electroacupuncture effectively reduces BP and HR increases and plasma catecholamine increases in rats challenged with immobilization stress.

Maximal electroshock seizure threshold (MEST) is a classical measure of seizure sensitivity with a wide range of experimental applications. We determined MEST in nine inbred mouse strains and one congenic strain using a procedure in which mice are given one shock per day with an incremental (1 mA) current increase in each successive trial until a maximal seizure (tonic hindlimb extension) is elicited. C57BL/6J and DBA/2J mice exhibited the highest and lowest MEST, respectively, with the values of other strains falling between these two extremes. The relative rank order of MEST values by inbred strain (highest to lowest) is as follows: C57BL/6J > CBA/J = C3H/HeJ > A/J > Balb/cJ = 129/SvIMJ = 129/SvJ > AKR/J > DBA/2J. Results of experiments involving a single electroconvulsive shock given to separate groups of mice at different current intensities suggest that determination of MEST by the method used is not affected by repeated sub-maximal seizures. Overall, results document a distinctive mouse strain distribution pattern for MEST. Additionally, low within strain variability suggests that environmental factors which affect quantification of MEST are readily controlled under the conditions of this study. We conclude that MEST represents a useful tool for dissecting the multifactorial nature of seizure sensitivity in mice.

We conducted a quantitative trait locus (QTL) mapping study to dissect the multifactorial nature of maximal electroshock seizure threshold (MEST) in C57BL/6 (B6) and DBA/2 (D2) mice. MEST determination involved a standard paradigm in which 8- to 12-week-old mice received one shock per day with a daily incremental increase in electrical current until a maximal seizure (tonic hindlimb extension) was induced. Mean MEST values in parental strains were separated by over five standard deviation units, with D2 mice showing lower values than B6 mice. The distribution of MEST values in B6xD2 F2 intercrossed mice spanned the entire phenotypic range defined by parental strains. Statistical mapping yielded significant evidence for QTLs on chromosomes 1, 2, 5, and 15, which together explained over 60% of the phenotypic variance in the model. The chromosome 1 QTL represents a locus of major effect, accounting for about one-third of the genetic variance. Experiments involving a congenic strain (B6.D2-Mtv7(a)/Ty) enabled more precise mapping of the chromosome 1 QTL and indicate that it lies in the genetic interval between markers D1Mit145 and D1Mit17. These results support the hypothesis that the distal portion of chromosome 1 harbors a gene(s) that has a fundamental role in regulating seizure susceptibility.

Extracellular dopamine levels were determined by microdialysis in the core and shell of the nucleus accumbens and the frontal cortex of rats before and after an injection of cocaine (20 mg/kg, IP). After removal of the probes, these same animals were then tested for their voluntary intake of cocaine using the two-bottle, free-choice paradigm. Baseline dopamine levels and their responses to an injection of cocaine differed among the three brain areas. No significant correlations were found between baseline dopamine levels in any of the three brain regions and the voluntary cocaine consumption. A significant negative correlation was found between cocaine-induced increases in extracellular dopamine in the shell of the nucleus accumbens and the voluntary intake of cocaine (r = -0.73, p < 0.01). No such correlations were observed in the accumbens core region or the frontal cortex. These results provide further evidence of the role of the accumbal shell region in cocaine preference, and indicate that cocaine-induced increases in dopamine levels play a role in oral cocaine self-administration or preference. In addition, this relatively novel approach in using the same animals for both cocaine induced neurotransmitter responses and cocaine preference studies can also be applied for the study of other neurotransmitters and drugs of abuse.

DBA/2J (D2) and C57BL/6J (B6) mice exhibit differential sensitivity to seizures induced by various chemical and physical methods, with D2 mice being relatively sensitive and B6 mice relatively resistant. We conducted studies in mature D2, B6, F1, and F2 intercross mice to investigate behavioral seizure responses to pentylenetetrazol (PTZ) and to map the location of genes that influence this trait. Mice were injected with PTZ and observed for 45 min. Seizure parameters included latencies to focal clonus, generalized clonus, and maximal seizure. Latencies were used to calculate a seizure score that was used for quantitative mapping. F2 mice (n = 511) exhibited a wide range of latencies with two-thirds of the group expressing maximal seizure. Complementary statistical analyses identified loci on proximal (near D1Mit11) and distal chromosome 1 (near D1Mit17) as having the strongest and most significant effects in this model. Another locus of significant effect was detected on chromosome 5 (near D5Mit398). Suggestive evidence for additional PTZ seizure-related loci was detected on chromosomes 3, 4, and 6. Of the seizure-related loci identified in this study, those on chromosomes 1 (distal), 4, and 5 map close to loci previously identified in a similar F2 population tested with kainic acid. Results document that the complex genetic influences controlling seizure response in B6 and D2 mice are partially independent of the nature of the chemoconvulsant stimulus with a locus on distal chromosome 1 being of fundamental importance.

Agarose gel electrophoresis with ethidium bromide staining (AGE/EBS) is an efficient and reliable method for analyzing microsatellite polymorphisms. We report the use of AGE/EBS for analyzing DNA microsatellite polymorphisms in a preliminary quantitative trait loci (QTL) study of seizure susceptibility in which a candidate gene strategy was used to direct initial mapping efforts. F2 intercross progeny, derived from seizure-sensitive DBA/2J (D2) and seizure-resistant C57BL/6J (B6) inbred strains of mice, were tested for their sensitivity to the seizure-inducing effect of pentylenetetrazol (PTZ), a gamma-aminobutyric acid (GABA) receptor antagonist. A semi-automated method is described, in which DNA microsatellites were amplified by polymerase chain reaction (PCR) to yield products of 100-200 base pair (bp) in length. Alleles were separated on 3-6% MetaPhor agarose gels, stained with ethidium bromide, and visualized by ultraviolet (UV) illumination. Univariate analysis of genotype and phenotype data provides evidence for a seizure-related QTL on chromosome 5, near genes coding for the GABAA receptor subunits alpha 5 and gamma 3. Interestingly, this suggestive QTL derives from the more resistant B6 strain, but it nonetheless provides impetus for the characterization of possible strain differences in these two candidate genes. Overall, these results demonstrate that AGE/EBS can be useful for rapid screening of genomic regions of special interest in QTL mapping studies.

C57BL/6J (B6) and DBA/2J (D2) mice have been characterized previously as seizure-resistant and seizure-sensitive, respectively, a distinction based primarily upon a differential response to the convulsant effects of various drugs. In the present study, electroconvulsive shock (ECS) was used to assess maximal electroshock threshold (MET) in B6, D2 and hybrid mice. Results revealed that D2 mice have a significantly lower MET compared to B6 mice. There was also a significant gender effect for B6 and F2 mice with females exhibiting a lower MET compared to males. METs for F1 and F2 intercross mice were intermediate between the two parental strains. The difference in variance between F2 and F1 generation mice indicated that about three-quarters of the total variance is due to genetic influence. Taken together, results of this study suggest that the large difference in MET between B6 and D2 mice is a highly heritable trait which may yield to genetic dissection through use of quantitative trait locus mapping., (Copyright 1998 Elsevier Science B.V.)

The clinicopathological phenotype of the Gerstmann-Sträussler-Scheinker disease (GSS) variant linked to the codon 102 mutation in the prion protein (PrP) gene (GSS P102L) shows a high heterogeneity. This variability also is observed in subjects with the same prion protein gene PRNP haplotype and is independent from the duration of the disease. Immunoblot analysis of brain homogenates from GSS P102L patients showed two major protease-resistant PrP fragments (PrP-res) with molecular masses of approximately 21 and 8 kDa, respectively. The 21-kDa fragment, similar to the PrP-res type 1 described in Creutzfeldt-Jakob disease, was found in five of the seven subjects and correlated with the presence of spongiform degeneration and "synaptic" pattern of PrP deposition whereas the 8-kDa fragment, similar to those described in other variants of GSS, was found in all subjects in brain regions showing PrP-positive multicentric amyloid deposits. These data further indicate that the neuropathology of prion diseases largely depends on the type of PrP-res fragment that forms in vivo. Because the formation of PrP-res fragments of 7-8 kDa with ragged N and C termini is not a feature of Creutzfeldt-Jakob disease or fatal familial insomnia but appears to be shared by most GSS subtypes, it may represent a molecular marker for this disorder.

Glutamate and its receptors represent the major excitatory neurotransmission system in the mammalian brain and are considered important in the pathogenesis of many neurological diseases. The present study describes saturation binding experiments performed to measure the affinity (Kd) and density (Bmax) of kainate and AMPA receptors in striatum, cortex and hippocampus from mature DBA/2J (DBA) and C57BL/6J (C57) mice. Previous studies have documented that these two strains differ significantly in seizure susceptibility, with DBA mice exhibiting greater sensitivity in various convulsant tests compared to C57 mice. Non-linear regression analysis of binding data together with Student's t-test and ANOVA revealed significantly higher densities of kainate receptors in striatum and of AMPA receptors in cortex of DBA mice. C57 mice exhibited higher striatal [3H]AMPA binding. There were no significant differences between the mouse strains in binding sites prepared from hippocampus and no differences in affinity for either receptor in any brain region studied. The results support a role for kainate and AMPA receptors in seizure sensitivity, possibly by influencing glutamate transmission in specific pathways. It is unlikely, however, that these receptors account for the generation of seizures alone but rather cooperate with other glutamatergic and non-glutamatergic neurotransmitter systems.

Mature DBA/2J (D2) mice are very sensitive to seizures induced by various chemical and physical stimuli, whereas C57BL/6J (B6) mice are relatively seizure resistant. We have conducted a genome-wide search for quantitative trait loci (QTLs) influencing the differential sensitivity of these strains to kainic acid (KA)-induced seizures by studying an F2 intercross population. Parental, F1, and F2 mice (8-10 weeks of age) were injected subcutaneously with 25 mg/kg of KA and observed for 3 h. Latencies to focal and generalized seizures and status epilepticus were recorded and used to calculate an overall seizure score. Results of seizure testing indicated that the difference in susceptibility to KA-induced seizures between D2 and B6 mice is a polygenic phenomenon with at least 65% of the variance due to genetic factors. First-pass genome screening (10-cM marker intervals) in F2 progeny (n = 257) documented a QTL of moderate effect on Chromosome (Chr) 1 with a peak LOD score of 5.5 (17% of genetic variance explained) localized between D1Mit30 and D1Mit16. Provisional QTLs of small effect were detected on Chr 11 (D11Mit224-D11Mit14), 15 (D15Mit6-D15Mit46) and 18 (D18Mit9-D18Mit144). Multiple locus models generally confirmed the Mapmaker/QTL results and also provided evidence for another QTL on Chr 4 (D4Mit9). Multilocus analysis of seizure severity suggested that additional loci on Chrs 5 (D5Mit11), 7 (D7Mit66), and 15 (D15Nds2) might also contribute to KA-induced seizure response. Overall, our results document a complex genetic determinism for KA-induced seizures in these mouse strains with contributions from as many as eight QTLs.

C57BL/6J (B6) mice self-administer substantial quantities of morphine compared to DBA/2J (D2) mice, and most of the genetic component of this strain difference has been attributed to a locus on chromosome 10 in the vicinity of the mu opioid receptor gene. To compare binding characteristics of mu opioid receptor populations between the two strains, mice were given single daily injections of a long-acting preparation of morphine sulfate (80 mg/kg, s.c.) or saline for a period of seven days, and euthanatized six hours after the last injection. Brains were removed and dissected into specific regions. Receptor binding studies were performed on frontal cortex and striatum. Data were analyzed using non-linear regression, and Kd and Bmax comparisons made between strains and treatments. Specific [3H]DAMGO binding in striatum indicates that the density of mu opioid receptors in saline-treated B6 mice and saline-treated D2 mice does not differ significantly. After repeated morphine injection, B6 mice exhibited a decrease in striatal [3H]DAMGO binding, indicating a downregulation of receptor density by approximately 45% (p=.0003 vs saline-treated B6), a phenomenon not observed in D2 mice. In frontal cortex, no differences in [3H]DAMGO binding were observed between strains or treatment groups. These results demonstrate a significant difference between mu opioid receptor regulation in B6 and D2 mice, and may underlie well documented strain differences in specific opioid-related behaviors.

Mature DBA/2J (D2) and C57BL/6J (B6) mice aged 9-10 weeks were studied to determine susceptibility to behavioral seizures induced by kainic acid (KA) and the possible influence exerted by differences in metabolism and blood-brain barrier (BBB) transport. Mice were observed for 4 h after subcutaneous (s.c.) KA injection. Behavioral seizure parameters included latency to first seizure (clonus), latency to tonic/clonic seizure, and latency to status epilepticus (SE). At a KA dose of 25 mg/kg, 80% of D2 mice exhibited tonic/clonic seizures, whereas all B6 mice remained seizure-free. At 30 mg/kg, tonic/clonic seizures were observed in 100% of D2 mice and 25% of B6 mice. Of D2 mice exhibiting at least one clonic seizure in response to KA at a dose of 25 mg/kg, 50% entered SE and eventually died. Administration of [3H]KA (6.6 x 10(6) dpm) at doses of 25 mg/kg (convulsive) or 11.1 micrograms (nonconvulsive) to mice of both strains resulted in similar levels of radioactivity in cortex, hippocampus, and cerebellum 30 and 60 min after injection. Bioconversion of [3H]KA to a radiolabeled brain metabolite in vivo could not be documented in mice from either strain. Results confirm previously reported differences between D2 and B6 mice in their relative susceptibility to seizures induced by systemic KA administration and suggest that these differences are not related to strain-specific variation in metabolism or BBB transport of KA. Further studies of these two strains of mice may be useful for investigating genetic influences upon seizure susceptibility.

This study reports comparative dose-response data for kainic acid (KA) induced seizures in juvenile (35-40 days old) and adult (70-90 days old) Wistar-Furth (WF), Fisher 344 (F344), Sprague-Dawley (SD) and Long-Evans Hooded (LEH) rats. Juvenile male WF (n = 51), F344 (n = 55), SD (n = 60), LEH (n = 50) and adult male WF (n = 48), F344 (n = 52), SD (n = 52), LEH (n = 53) rats were given KA 6, 8, 10, 12 or 14 mg/kg, sc. As previously demonstrated adult WF and F344 rats showed the greatest sensitivity and most reliable convulsant responses to kainic acid; SD and LEH rats were less sensitive and showed more variable convulsant responses. Regardless of strain, all juvenile rats exhibited greater sensitivity and less variable convulsant response to KA compared to adults. This was most evident in juvenile SD and LEH rats. Results suggest that while seizure sensitivity to KA decreases with age, genetic factors may regulate the expression of this resistance.

Striatal dopamine (DA) release was measured following intrastriatal (i.s.) administration of N-methyl-D-aspartate (NMDA) to unanesthetized, freely-moving rats. One hour after insertion of a removable microdialysis probe and perfusion with normal Ringer's solution, a modified Ringer's solution containing 100 mM potassium (high-K+ Ringer's) was used to standardize the preparation. DA release following i.s. administration of NMDA (12.5 mM in normal Ringer's) was dose-dependent. When NMDA (12.5 mM) was administered in high-K+ Ringer's, DA release was greatly potentiated. Administration of the competitive NMDA receptor antagonist aminophosphonovalerate (APV) in normal Ringer's prior to treatment with NMDA in high-K+ Ringer's resulted in a significant reduction of DA release compared to control animals. In contrast, administration of APV priot to treatment with NMDA in normal Ringer's resulted in a significantly increased release of DA compared to controls. Administration of the non-competitive NMDA antagonist, dextromethorphan (DXT) prior to treatment with NMDA in normal Ringer's or NMDA in high-K+ Ringer's caused significant reductions of DA release compared to controls. Intrastriatal DXT also caused dose-dependent inhibition of high-K+ Ringer's-induced DA release. Similarly, administration of the non-specific calcium channel blocker, cadmium, prior to treatment with NMDA resulted in a significant decrease when compared to control values. Results of this study indicate that dose-dependent NMDA-induced striatal DA release is greatly potentiated by potassium suggesting that under physiological conditions in vivo, striatal NMDA receptors are mostly inactivated.(ABSTRACT TRUNCATED AT 250 WORDS)

The aim of this study was to characterize interactions between striatal kainate (KA) receptors and dopamine (DA) release using in vivo microdialysis. After insertion of a microdialysis probe and establishment of baseline DA release, each preparation was standardized with a pulse of an iso-osmotic solution of 100 mM KCl in Ringer's solution. DA release following pharmacological manipulation was compared to potassium-induced release and expressed as a percent value. In one group of animals, KA (12.5 mM in Ringer's solution) was administered via the microdialysis probe in 2, 3, 5 or 10 min pulses 30 min following standardization with potassium resulting in release of DA which was 15.7 +/- 3.9, 30.3 +/- 11.3, 67.5 +/- 15.0 and 92.9 +/- 19.8% of potassium-induced DA release, respectively. Perfusion of CdCl2 (0.6 mM in Ringer's solution) 30-45 min prior to a 10 min KA pulse significantly reduced KA-induced DA release compared to control values. Intrastriatal administration of kynurenate (Kyn) attenuated KA-induced DA release in a dose-dependent manner. Levels of DA metabolites in striatal perfusates were significantly reduced following KA administration. This effect was partially reversed by cadmium pretreatment but not affected by Kyn pretreatment. Findings of this study indicate that KA induces striatal DA release in a dose-dependent manner, and this effect is at least partially dependent upon activation of calcium channels. Results also indicate dose-dependent inhibition of KA-induced striatal DA release by the excitatory amino acid receptor antagonist, Kyn, suggesting that this compound interacts with striatal KA receptors and that these receptors are involved with modulating striatal DA release in vivo.

We describe a strain of rats (Wistar-Furth) that is highly susceptible to the neurotoxic effects of kainic acid (KA) and presents a reliable and quantifiable (with low within-group variability) animal model of status epilepticus. Wistar-Furth rats are more sensitive and demonstrate a less variable convulsant response than Sprague-Dawley and Long-Evans rats when tested for total time in seizure activity, latency to onset of first seizure, latency to status epilepticus, seizure severity scores, and percentage exhibiting behavioral seizures and status epilepticus. Results suggest that significant heterogeneity exists in the rodent population with regard to neuronal sensitivity to an excitotoxic amino acid and indicate that strain differences are an important consideration in studies using KA.

The neurochemical mechanisms of electroconvulsive therapy (ECT) are not fully elucidated. We examined the effects of electroconvulsive shock (ECS) on brain gamma-aminobutyric acid (GABA) systems. Male Wistar-Furth rats were given ECS via auricular (ear-clip) or corneal electrodes once per day (120 V, 0.5 s) for 10 consecutive days. Two groups of sham ECS rats, one for auricular placement and one for corneal placement, served as controls. Current was measured and seizures were scored during each ECS trial. Rats receiving ECS via corneal electrodes were subjected to more electrical current compared to rats treated with auricular electrodes. Although both groups exhibited behavioral seizures of similar duration, electrode placement had a differential influence on the expression of tonic hindlimb extension and clonic hindlimb activity over the 10-day regimen. GABA levels were increased in all brain regions examined in rats treated with auricular electrodes except the hippocampus and nucleus accumbens; rats treated with corneal electrodes exhibited GABA increases in the hippocampus, frontal cortex, hypothalamus, and olfactory bulbs; a significant decrease in nucleus accumbens; and no change in the substantia nigra and striatum. The mode of ECS delivery selectively alters the pattern of regional alterations of brain GABA level induced by ECS. This effect may be a function of current intensity or localization.

Discharges of single cells in the thalamic mediodorsal nucleus (MD) of the opossum were recorded during electrical stimulation of the lateral olfactory tract. Responsive sites were histologically localized throughout the entire mediolateral extent of MD. In both rabbit and squirrel monkey responses are confined to the medial half of MD. Thus the lateral non-olfactory nuclear subdivision, common to both rabbit and squirrel monkey, was not found in the opossum. Firing patterns of cells were similar to those observed in rabbit and squirrel monkey. They commonly consisted of an early spike or burst of spikes, followed by a period of inactivity and then, in many cells, by a later period of response or of resumed spontaneous activity. The results indicate that olfactory input is characteristic of MD in a diverse sample of mammals but that topographic organization of the input is distinctly different in the opossum.

Infection within the peritoneal cavity without an identifiable source of contamination is rare. The diagnosis is one of exclusion, and can be made with certainty only after a thorough laparotomy. The response to antibiotic therapy is usually prompt and gratifying.

Homotaurine and taurine are two powerful inhibitory aminoacids with anticonvulsant properties against various experimental models of focal epilepsy. This study reports on their effects in the feline model of corticoreticular epilepsy induced by parenteral administration of large amounts of penicillin. Both aminoacids, but particularly homotaurine, remarkably potentiate epileptiform discharges in cats. Brainstem transection at the precollicular level does not modify the activation, thus ruling out the intervention of mesoromboencephalic structures in the observed effect. The opposing action of these two amino acids on focal epilepsy as compared to corticoreticular epilepsy suggests that the two types of epileptiform activity stem from very different pathophysiological mechanisms. Homotaurine is a powerful GABA agonist that exerts a central action upon parenteral administration. Other GABA analogs such as muscimol, imidazole acetic acid, and gamma-hydroxybutyrate have been reported to potentiate experimental models of spike and wave epilepsy. Thus, the activating effects of homotaurine in this epilepsy model are in keeping with the demonstrated GABAmimetic properties of the compound.

Direct GABA agonists that suppress spikes induced by penicillin in cats failed to do so in rats. Phenytoin and large doses of THIP increased the rate of spiking activity of the penicillin focus. Only progabide caused marked, initial, short-lasting suppression and a modest reduction of frequency of spikes for 1 hr. Homotaurine (3APS) reduced the amplitude and changed the morphology of the contralateral "mirror" spike. Antagonism of penicillin-induced spikes in rats is considered to be an unsuitable parameter for the screening of anticonvulsant agents.

Intracerebral injection of L-acetylcarnitine in rats induced interictal and ictal epileptic phenomena with immediate onset, lasting up to 4 h. Pretreatment with systemic atropine prevents all epileptiform phenomena. Local injection of muscimol and THIP abolish ictal events, but not single spikes. L-carnitine induced only ictal discharges with a latency of 40-90 min. Acetylcarnitine epileptogenic properties are probably related to muscarinic agonism. The transition from interictal to ictal events may involve failure of GABAergic mechanisms.

A new filtered sump tube has been designed for drainage of collections of fluids from wounds without the danger of infection by airborne contaminants. A two-staged filter has been attached to the vent lumen that removes particulate matter and bacteria from the air that passes through the filter. A clinical evaluation of this tube confirms the superiority of sump drainage as compared with closed suction drainage in the removal of fluids from wounds or cavities.

An ultrasensitive triple-column ion-exchange/fluorometric method was utilized to measure the levels of over 30 amino acids and related primary amino compounds in Long-Evans rat superior colliculus (SC), visual cortex (VC) and inferior colliculus (IC). Comparison of levels of amino compounds revealed distinctly different profiles for each region. Major constituents were the neurotransmitters and related compounds glutamate, glutamine, GABA, taurine, aspartate and glycine. Glutathione levels were also relatively high in all three regions. SC exhibited a significantly higher level of GABA and beta-alanine compared to both VC and IC. VC had significantly higher levels of glutamate and taurine. VC exhibited the lowest level of glycine and IC the highest. A time-course experiment using SC documented that levels of eleven of thirty-four compounds, including GABA, were subject to significant postmortem alteration in vitro. SC GABA stability experiments indicated that significant in vitro increases of free GABA levels between 1 and 4 min postmortem were associated with equimolar decreases of conjugated GABA levels.

A review of the literature discloses 56 cases of bronchial adenoma in children under the age of 16 years; we now report two additional cases. The diagnosis of bronchial adenoma in children is often delayed due to erroneous interpretation of the secondary manifestations of pneumonitis, fever, or wheezing. These tumors should be considered potentially malignant, since local invasion and metastasis have been reported in this age group. Treatment is by thoracotomy with total excision of the lesion.

Cortical superfusion with 6-aminomethyl-3-methyl, 1-4H-1,2,6-benzothiadiazine-1,1-diazide hydrocholoride (TAG) at a concentration which selectively blocks taurine (Tau) action fails to modify electroencephalographic (EEG) activity, cortical neuronal firing and caudate-induced inhibition of cortical neuronal activity. Higher concentrations of TAG increase neuronal firing rate and eventually induce EEG interictal spikes that can be suppressed by topical gamma-aminobutyric acid (GABA), but not by glycine or beta-alanine. Topical Tau consistently enhances the epileptiform activity. It is concluded that specific blockade of Tau does not affect any of the physiological function under observation and that the epileptogenic effect of TAG is due to its GABA antagonistic action.

Misleading pneumoperitoneum takes one of two forms: true pneymoperitoneum without peritonitis or pneumoperitoneum simulated by adventitious x-ray shadows. In both instances, the roentgenographic appearance of free intraperitoneal air proves to be a specious indication for laparotomy. Twenty-eight per cent of 29 patients with misleading pneumoperitoneum were subjected to operations that, retrospectively, might not seem absolutely necessary. The decisions to operate on patients with pneumoperitoneum without peritonitis were based on the amount of pneumoperitoneum roentgenographically visualized. The instances of pseudopneumoperitoneum had several common features. The diagnosis often was based only on x-ray films of the chest. Compatibility with clinical features was marginal; the radiolucency was often not truly at the apex of the diaphragm. Finally, the x-ray films, interpretation and working conditions frequently were suboptimal.