The youngest infant with COVID-19-associated necrotizing encephalitis in Asia: A case report

Acute necrotic encephalopathy in children is a very rare complication of severe acute respiratory syndrome coronavirus 2 infection and has rarely been reported worldwide. A 45-day-old girl was admitted to our hospital with fever and listlessness. A nose swab tested positive for the novel coronavirus nucleic acid, and her cerebrospinal fluid was positive for severe acute respiratory syndrome coronavirus 2. An early head magnetic resonance imaging scan indicated multiple abnormal signals in her bilateral cerebral hemispheres, and encephalitis was diagnosed. Twenty-three days after hospitalization, bilateral cerebral atrophy-like changes were observed on magnetic resonance imaging, with multiple softening lesions in the bilateral cerebral hemispheres, accompanied by convulsions. She was admitted to the hospital for mechanically assisted ventilation, and her condition improved after treatment of her symptoms with antiepileptic medication, anti-infection drugs, glucocorticoids, and immunoglobulins. Acute necrotic encephalopathy associated with severe acute respiratory syndrome coronavirus 2 infection in children should be detected and treated as early as possible. Satisfactory short-term efficacy can be obtained, but long-term neurological sequelae often linger.

[Effect of early continuous blood purification on the prognosis of children with septic shock: a prospective randomized controlled clinical trial]

OBJECTIVE

To study the effect of early continuous blood purification (CBP) on the prognosis of children with septic shock.

METHODS

A prospective analysis was performed for the children with septic shock who did not reach the 6-hour initial recovery target and/or had a fluid overload of >10%. According to the treatment time of CBP, they were divided into an early group with 30 children and a conventional group with 28 children. The two groups were compared in terms of the start time of CBP and 28-day mortality rate, as well as the related indexes in the children who were cured.

RESULTS

The early group had a significantly earlier start time of CBP than the conventional group (P<0.05). There were 25 children cured in the early group and 22 cured in the conventional group, and there was no significant difference in 28-day mortality rate between the two groups (P>0.05). The children who were cured in the early group had significantly shorter correction time of lactic acid, urine volume, and fluid overload than those in the conventional group (P<0.05). The children who were cured in both groups had significant reductions in the percentages of T-lymphocyte subsets at the beginning (P<0.05); on reexamination on day 7, the percentages of T-lymphocyte subsets were increased and were higher in the early group than in the conventional group (P<0.05). The children who were cured in the early group had significantly shorter duration of CBP treatment, duration of mechanical ventilation, and length of stay in the PICU than those in the conventional group (P<0.05).

CONCLUSIONS

For children with septic shock who do not reach the 6-hour initial recovery target and/or have a fluid overload of >10%, early CBP treatment can quickly control the disease, shorten the course of disease, and accelerate immune reconstruction.

[Effect of early continuous blood purification on the prognosis of children with septic shock: a prospective randomized controlled clinical trial]

OBJECTIVE

To study the effect of early continuous blood purification (CBP) on the prognosis of children with septic shock.

METHODS

A prospective analysis was performed for the children with septic shock who did not reach the 6-hour initial recovery target and/or had a fluid overload of >10%. According to the treatment time of CBP, they were divided into an early group with 30 children and a conventional group with 28 children. The two groups were compared in terms of the start time of CBP and 28-day mortality rate, as well as the related indexes in the children who were cured.

RESULTS

The early group had a significantly earlier start time of CBP than the conventional group (P<0.05). There were 25 children cured in the early group and 22 cured in the conventional group, and there was no significant difference in 28-day mortality rate between the two groups (P>0.05). The children who were cured in the early group had significantly shorter correction time of lactic acid, urine volume, and fluid overload than those in the conventional group (P<0.05). The children who were cured in both groups had significant reductions in the percentages of T-lymphocyte subsets at the beginning (P<0.05); on reexamination on day 7, the percentages of T-lymphocyte subsets were increased and were higher in the early group than in the conventional group (P<0.05). The children who were cured in the early group had significantly shorter duration of CBP treatment, duration of mechanical ventilation, and length of stay in the PICU than those in the conventional group (P<0.05).

CONCLUSIONS

For children with septic shock who do not reach the 6-hour initial recovery target and/or have a fluid overload of >10%, early CBP treatment can quickly control the disease, shorten the course of disease, and accelerate immune reconstruction.

Two copper(II) coordination polymers constructed by bis(4-(1H-imidazol-1-yl)phenyl)methanone and dicarboxylate ligands

Two new copper(II) complexes, {[Cu(bipmo)(npa)]} n (1) and {[Cu(bipmo)(pa)]} n (2) (bipmo=bis(4-(1H-imidazol-1-yl)phenyl)methanone), were synthesized by solvothermal methods and structurally characterized by elemental analyses, infrared spectroscopy, and single-crystal X-ray diffraction. The results from single-crystal X-ray diffraction data indicate that the solid state structures of 1 and 2 consist of neutral metal aromatic carboxylate layers, which are pillared by the weak interactions to generate 3D architectures. The topological structures of 1 and 2 are uninodal nets based on 4-connected nodes with the Schläfli symbol of (65·8).

Syntheses, crystal structures, and characterization of two Mn(II) coordination polymers with bis(4-(1H-imidazol-1-yl)phenyl)methanone ligands

Two Mn(II) complexes, {[Mn(BIPMO)2Cl2] · 2(H2O)} n (1) and {[Mn(BIPMO)2(SCN)2] · 2(CH3OH)} n (2) (BIPMO = bis(4-(1H-imidazol-1-yl)phenyl)methanone) with V-shaped BIPMO ligands, were synthesized and characterized by IR spectroscopy and elemental analyses along with their single-crystal X-ray diffraction analyses. The Mn(II) ions in 1 and 2 are both six-coordinated to four nitrogen atoms of four BIPMO ligands and two anions (Cl− for 1, and SCN− for 2) to form a distorted octahedral geometry.

Application of the ERK signaling pathway inhibitor PD98059 in long-term in vivo experiments

The aim of this study was to explore methods by which the ERK signaling pathway inhibitor PD98059 (PD) could be used in long-term in vivo experiments. Forty healthy New Zealand rabbits were randomly divided into blank control, model control, PD low-dose, PD high-dose, PD blank, dimethyl sulfoxide (DMSO) control, DMSO blank, and positive control groups. The corresponding treatments were administered to each experimental group over the course of four weeks, after which, total ERK1/2 and ERK5 protein levels, protein phosphorylation, and gene expression were measured in myocardial tissues. Treatment of rabbits with Adriamycin (doxorubicin) resulted in the significant overall differences in ERK1/2 and ERK5 phosphorylation (P < 0.05). Compared with the model control group, changes in phosphorylated ERK1/2 and phosphorylated ERK5 were lowest in the PD high-dose group (P < 0.05). No significant differences in total protein and mRNA levels of myocardial ERK1/2 and ERK5 were detected between the groups after four weeks (P > 0.05). Continuous intravenous injection of PD98059 significantly reduced phosphorylation of ERK1/2 and that of ERK5. In conclusion, Adriamycin-induced myocardiopathy and abnormal ERK signaling might constitute a valuable model foruse in long-term experiments. These methods may provide a theoretical basis for related in vivo studies of long duration.

Synthesis of peptides of Carapax Trionycis and their inhibitory effects on TGF-β1-induced hepatic stellate cells

We previous identified the antifibrotic active ingredients from Carapax Trionycis as two peptides. Here, we synthesized these two peptides (peptide 1 and peptide 2) by a solid phase method and examined their effects on proliferation and activation of cultured hepatic stellate cells (HSC) which are the main ECM (extracellular matrix)-producing cells in fibrosis progression. We demonstrated that peptide 1 and peptide 2 significantly reduced HSC proliferation and activation in a dose dependent manner. Further, peptide 1 and peptide 2 could interfere with TGF-signaling by down-regulating Smad 3 phosphorylation. Thus, these synthetic peptides of Carapax Trionycis could inhibit proliferation and activation of HSC and might be used as a candidate for treatment of liver fibrosis.

Developmental changes in BDNF protein in the song control nuclei of zebra finches

The zebra finch song system provides an excellent model to study the mechanisms underlying the development of sex difference in brain structure and function. Only male zebra finches sing and the brain nuclei controlling song learning and production are considerably larger than in females. Sexual differentiation may in part be regulated by estrogen, but other molecules including neurotrophic factors likely also affect masculinization. Brain derived neurotrophic factor (BDNF) plays a crucial role in numerous aspects of vertebrate brain development and function, including neurogenesis, cell survival, growth of axonal projections, synaptogenesis and processes linked to learning and memory. The current study investigated the expression of BDNF protein in juvenile males and females at four ages, as well as in adults, to begin to evaluate the potential roles of endogenous BDNF in particular stages of structural and functional development of the song system. In both HVC and the robust nucleus of the arcopallium (RA), males had more BDNF+ cells than females. The number of immunopositive cells increased in males and decreased in females as they matured, in a pattern generally consistent with a role for BDNF in sensorimotor integration of song learning. In addition, in HVC (but not RA) the ratio of mature BDNF compared to its precursor proBDNF was greater in adult males than those at post-hatching day 25, indicating a region-specific shift in the relative availability of the two forms. Collectively, the data suggest that changes in BDNF protein expression across development may be associated with song system maturation, particularly during the sensorimotor integration of masculine vocalizations.

Bioactive components in the fruits of Ziziphus jujuba Mill. against the inflammatory irritant action of Euphorbia plants

Chinese jujube (also known as Chinese date) is the fruit of Ziziphus jujuba Mill. (Rhamnaceae). As a famous folk medicine, it is used as antidote in traditional Chinese formula, Shi Zao Decoction, to relieve the drastic inflammatory irritant nature of Euphorbia species. The irritant activities may cause serious adverse effects in clinical practices. This study aimed to investigate the active components of Z. jujuba through the inhibitory effects on the inflammatory cells activated by Euphorbia kansui and prostratin, a phorbol ester isolated from Euphorbia fischeriana. Peritoneal macrophage of rat and splenic lymphocyte (splenocyte) of mouse were selected to evaluate these actions in vitro. Nitric oxide (NO) release of macrophage and the proliferation of splenocyte were examined through Griess method and MTT assay. TNF-α, as an important pro-inflammatory cytokines, was detected with enzyme-linked immunosorbent assay (ELISA) method. Six fractions extracted from Z. jujuba were evaluated and fraction F (triterpene acids fraction) was demonstrated to be the most active part, and then, 21 compounds isolated from Z. jujuba were tested at the concentrations range from 1 μg/ml to 100 μg/ml. The results show that 7 compounds of them are likely to be active compounds concerning to their pronounced inhibitory action on the activated inflammatory cells. These effects might be helpful to attenuate the irritant action of Euphorbiaceae plants and protect the gastrointestinal tissue from potent inflammatory injury, which should be beneficial to some diseases, like inflammatory bowel disease.

Developmental changes in the sexually dimorphic expression of secretory carrier membrane protein 1 and its co-localisation with androgen receptor protein in the zebra finch song system

The song system of zebra finches differs dramatically between the sexes in terms of both structure and function. Only males sing and the brain regions regulating the learning and production of this behaviour are far more developed in males than females. Mechanisms regulating sexual differentiation likely include both direct genetic and hormonal processes. Expression of both mRNA and the protein product for secretory carrier membrane protein 1 (SCAMP1), a sex chromosome gene, are increased in the brains of juvenile males compared to females. Here we investigated developmental changes in SCAMP1 containing cells in song nuclei and co-localisation with androgen receptor (AR) protein from post-hatching day 25 through adulthood. Almost all SCAMP1 cells co-expressed AR and approximately half of the AR cells expressed SCAMP1 in the HVC and robust nucleus in the arcopallium (RA) of both sexes and in the Area X of males (which could not be clearly defined in females). In HVC and RA, more single and double-labelled cells were detected in males than females overall, and the sex differences increased as animals matured. The results suggest the potential for interaction of these two proteins in regulating development of brain and/or behaviour.

Sex- and age-related differences in ribosomal proteins L17 and L37, as well as androgen receptor protein, in the song control system of zebra finches

The zebra finch song system is sexually dimorphic--only males sing, and the morphology of forebrain regions controlling the learning and production of this song is greatly enhanced in males compared to females. Masculinization appears to involve effects of steroid hormones as well as other factors, perhaps including the expression of sex chromosome genes (males: ZZ, females: ZW). The present study investigated three proteins--two encoded by Z-linked genes, ribosomal proteins L17 and L37 (RPL17 and RPL37), including their co-localization with androgen receptor (AR), from post-hatching day 25 to adulthood. Extensive co-expression of AR with the ribosomal proteins was detected in the three song nuclei investigated (HVC, robust nucleus of the arcopallium (RA), and Area X) across these ages. In general, more cells expressed each of these proteins in males compared to females, and the sex differences increased as animals matured. Specific patterns differed across regions and between RPL17 and RPL37, which suggest potential roles of one or both of these proteins in the incorporation and/or differentiation of song system cells.

Chemical correlation between Gegen Qinlian dispensing granule and its four raw herbs by LC fingerprint

Gegen Qinlian dispensing granule, a favorite composite formula, is a combination of Radix Puerariae Lobatae, Radix Scutellariae, Rhizoma Coptidis and Radix et Rhizoma Glycyrrhizae Praeparata cum Melle. To develop a method to overall evaluate correlation between the formula and its four raw herbs, LC fingerprints of the formula and its raw herbs were developed and LC-DAD-MS was employed to identify the components in the formula fingerprint. According to the characteristic fragmentation behavior of known flavonoids, alkaloids and saponins isolated from the four raw herbs as well as retention time, UV and MS data of detected compounds, a total of 23 constituents in the formula fingerprint were structurally characterized. Chemical correlation between the formula and the four crude herbs was evaluated qualitatively and quantitatively by the developed LC fingerprints. The results showed that 8 components in the formula fingerprint were addressed to Radix Puerariae Lobatae, 11 to Radix Scutellariae, 7 to Rhizoma Coptidis, 3 to Radix et Rhizoma Glycyrrhizae Praeparata cum Melle, and that the relative area ratios of the common peaks in the formula vary slightly in comparison with corresponding ratios in its crude herbs, demonstrating the chemical constituents in the formula have patterns similar to those in its crude herbs.

Management of attention deficit hyperactivity disorder: a parental perspective

OBJECTIVES

There are few studies exploring parental perceptions of the diagnosis and overall treatment of their children with attention deficit hyperactivity disorder (ADHD). This community-based study was conducted to consider this important aspect of care.

METHODS

A total of 7 226 (65%) parents responded to a community survey of 11 184 children aged 10-12 years living in northern Sydney in 2000, out of which 278 children with ADHD were identified. Their parents completed an anonymous questionnaire covering their perceptions relating to diagnosis, treatment and overall management.

RESULTS

Only 66% of parents recalled the use of questionnaires or rating scales. There were 82% of children who had trialed medication and 66% of these were still taking it. Behavioural intervention had occurred in 42% of the children. Non-conventional treatments, most commonly elimination diet and/or fatty acid supplementation, had been used in 71% of the children. These were considered helpful in one-third of cases. A total of 55% of parents reported being either satisfied or very satisfied with their child's care. Parents were more likely to report satisfaction when their children were on medication and when reviews were held at least 6 monthly. Lack of educational support and teachers' understanding of ADHD were identified as ongoing issues.

CONCLUSION

Parental responses suggested that adherence to recommended diagnostic guidelines was inadequate. Behavioural intervention was underutilized despite its documented positive role. Non-conventional therapies were widely used and considered helpful in one-third of the children who used them. Use of stimulant medication and frequent reviews were more likely to be associated with overall management satisfaction.

mRNA differential display identification of thyroid hormone-responsive protein (THRP) gene in association with early phase of long-term potentiation

The process of long-term potentiation (LTP) consists of the early induction and late maintenance phases. Few studies have examined the cellular mechanisms underlying these two phases; their respective mRNA expression profiles have not yet been elucidated. Here we used the technique of PCR differential display to identify genes that are differentially expressed between the early and late phases of LTP in vivo. Our results indicated that the cDNA fragment corresponding to one mRNA with preferentially increased expression during the early, but not late, phase of LTP encodes the rat thyroid hormone-responsive protein (THRP) gene. In situ hybridization analysis confirmed the results obtained from the PCR differential display. Prior NMDA receptor blockade with MK801 prevented induction of LTP and decreased THRP mRNA expression in the dentate gyrus, as assayed by quantitative RT-PCR analysis. THRP antisense oligonucleotide treatment before tetanic stimulation also prevented induction of LTP. However, when THRP antisense oligonucleotide was administered after induction of LTP, it did not affect expression and maintenance of LTP. THRP is known to be responsive to thyroid hormone. Our results indicate that direct thyroid hormone (T3) injection into the dentate gyrus produces a long-lasting enhancement of synaptic efficacy of these neurons. T3 injection also markedly increased THRP mRNA expression in the dentate gyrus. Taken together, our results suggest that THRP mRNA expression plays an important role in the early phase, but not the late phase, of LTP and that both THRP and thyroid hormone are involved in synaptic plasticity in hippocampal neurons.

Deficient neurogenesis in forebrain-specific presenilin-1 knockout mice is associated with reduced clearance of hippocampal memory traces

To examine the in vivo function of presenilin-1 (PS1), we selectively deleted the PS1 gene in excitatory neurons of the adult mouse forebrain. These conditional knockout mice were viable and grew normally, but they exhibited a pronounced deficiency in enrichment-induced neurogenesis in the dentate gyrus. This reduction in neurogenesis did not result in appreciable learning deficits, indicating that addition of new neurons is not required for memory formation. However, our postlearning enrichment experiments lead us to postulate that adult dentate neurogenesis may play a role in the periodic clearance of outdated hippocampal memory traces after cortical memory consolidation, thereby ensuring that the hippocampus is continuously available to process new memories. A chronic, abnormal clearance process in the hippocampus may conceivably lead to memory disorders in the mammalian brain.

[Two kaempferol triglycosides from pericarps of Sophora japonica L]

OBJECTIVE

To study the flavonol triglycosides in the pericarps of Sophora japonica.

METHOD

Various chromatographic techniques were used to isolate and purify the constituents. The structures were elucidated by chemical evidence and spectral analysis, especially by 2D NMR experiments.

RESULTS

Two kaempferol triglycosides were isolated and identified as kaempferol 3-O-beta-D-sophoroside-7-O-alpha-L-rhamnoside and kaempferol 3-O-(2"-O-beta-D-glucosyl)-beta-D-rutinoside.

CONCLUSION

Both of them were reported in S. japonica for the first time.

Effect of transgenic overexpression of NR2B on NMDA receptor function and synaptic plasticity in visual cortex

The NMDA receptor (NMDAR) is a heteromer comprised of NR1 and NR2 subunits. Mice that overexpress the NR2B subunit exhibit enhanced hippocampal LTP, prolonged NMDAR currents, and improved memory ( Tang et al., 1999). In the current study, we explored visual cortex plasticity and NMDAR function in NR2B overexpressing transgenic mice. Unlike the hippocampus, in vitro synaptic plasticity of the visual cortex was unaltered by NR2B overexpression. Consistent with the plasticity findings, NMDAR excitatory postsynaptic current (EPSC) durations from layer 2/3 pyramidal cells were similar in wild-type (wt) and transgenic (tg) mice. Furthermore, temporal summation of NMDAR EPSCs to 10, 20, and 40 Hz stimulation did not differ between cells from wt and tg mice. Finally, although in situ studies clearly demonstrate overexpression of NR2B mRNA in visual cortex, we failed to observe a significant elevation in the synaptic expression of NR2B protein. We conclude that the synaptic ratio of NR2B over NR2A in the NMDA receptor complex in the visual cortex is not significantly influenced by the transgene overexpression. These data suggest that mRNA availability is not a limiting factor for the synthesis of NR2B protein in the visual cortex, and support the hypothesis that levels of NR2A, rather than NR2B, normally determine the subunit composition of NMDARs in visual cortex.

Differential effects of enrichment on learning and memory function in NR2B transgenic mice

It has been known that environmental enrichment leads to better learning and memory in mice. However, the molecular mechanisms are not known. In this study, we used the 10th-12th of the NR2B transgenic (Tg) lines, in which the NMDA receptor function is enhanced via the NR2B subunit transgene in neurons of the forebrain, to test the hypothesis of the involvement of NMDA receptor function in enrichment-induced better learning and memory. Consistent with our previous results, both larger long-term potentiation (LTP) in the hippocampus and superior learning and memory were observed in naive NR2B Tg mice even after the 10th-12th generation of breeding. After enrichment, wild-type mice exhibited overall improvement in their performances in contextual and cued conditioning, fear extinctions, and novel object recognition tasks. Interestingly, the same enrichment procedures could not further increase the performance of NR2B Tg mice in contextual conditioning, cued conditioning, or fear extinction, thereby indicating that enhanced NMDA receptor function can occlude these enrichment effects. However, we found that in the novel object recognition task enriched NR2B Tg mice exhibited much longer recognition memory (up to 1 week), compared to that (up to 3 days) in naive NR2B Tg mice. Furthermore, our biochemical experiments showed that enrichment significantly increased protein levels of GluR1, NR2B, and NR2A subunits of glutamate receptors in both wild-type and NR2B Tg mice. Therefore, our results suggest an interactive nature of molecular pathways involved in both environmental and genetic NMDA receptor manipulations for enhancing learning and memory.

NMDA receptor-dependent synaptic reinforcement as a crucial process for memory consolidation

The hippocampal CA1 region is crucial for converting new memories into long-term memories, a process believed to continue for week(s) after initial learning. By developing an inducible, reversible, and CA1-specific knockout technique, we could switch N-methyl-D-aspartate (NMDA) receptor function off or on in CA1 during the consolidation period. Our data indicate that memory consolidation depends on the reactivation of the NMDA receptor, possibly to reinforce site-specific synaptic modifications to consolidate memory traces. Such a synaptic reinforcement process may also serve as a cellular means by which the new memory is transferred from the hippocampus to the cortex for permanent storage.

Effects of environmental enrichment on gene expression in the brain

An enriched environment is known to promote structural changes in the brain and to enhance learning and memory performance in rodents [Hebb, D. O. (1947) Am. Psychol. 2, 306-307]. To better understand the molecular mechanisms underlying these experience-dependent cognitive changes, we have used high-density oligonucleotide microarrays to analyze gene expression in the brain. Expression of a large number of genes changes in response to enrichment training, many of which can be linked to neuronal structure, synaptic plasticity, and transmission. A number of these genes may play important roles in modulating learning and memory capacity.

Enrichment induces structural changes and recovery from nonspatial memory deficits in CA1 NMDAR1-knockout mice

We produced CA1-specific NMDA receptor 1 subunit-knockout (CA1-KO) mice to determine the NMDA receptor dependence of nonspatial memory formation and of experience-induced structural plasticity in the CA1 region. CA1-KO mice were profoundly impaired in object recognition, olfactory discrimination and contextual fear memories. Surprisingly, these deficits could be rescued by enriching experience. Using stereological electron microscopy, we found that enrichment induced an increase of the synapse density in the CA1 region in knockouts as well as control littermates. Therefore, our data indicate that CA1 NMDA receptor activity is critical in hippocampus-dependent nonspatial memory, but is not essential for experience-induced synaptic structural changes.

Dihydroayapin, a new coumarin compound from Dendrobium densiflorum

A new coumarin named dihydroayapin (1) together with seven known compounds were isolated from the stems of Dendrobium densiflorum. On the basis of physicochemical and spectral evidences, the structure of 1 was established as 6,7-methylenedioxy-3,4-dihydrobenzopyran-2-one.

Isolation of Bacteroides fragilis mutants with in vivo growth defects by using Tn4400', a modified Tn4400 transposition system, and a new screening method

A modified version of the Bacteroides fragilis transposon Tn4400, designated Tn4400', enabling rapid isolation and analysis of B. fragilis mutants has been constructed. To identify potential virulence factors, Tn4400'-generated mutants were screened by a new method; this resulted in the isolation of 21 mutant strains with impaired growth characteristics on tissue culture monolayers but normal growth in rich medium anaerobically.

Identification and cloning of genes from Porphyromonas gingivalis after mutagenesis with a modified Tn4400 transposon from Bacteroides fragilis

Porphyromonas gingivalis is a gram-negative, black-pigmented, oral anaerobe strongly associated with adult periodontitis. Previous transposon mutagenesis studies with this organism were based on the Bacteroides transposon Tn4351. Characterization of Tn4351-disrupted genes by cloning has not been an efficient way to analyze large numbers of mutants and is further complicated by the high rate of cointegration of the suicide delivery vector containing Tn4351. In this study, we mutagenized P. gingivalis with a modified version of the Bacteroides fragilis transposon Tn4400. Plasmid pYT646B carrying the transposon was mobilized from Escherichia coli to P. gingivalis ATCC 33277 by conjugation. Both normal and inverse transposition frequencies were similar (3 x 10(-8)). However, the inverse transposon (Tn4400') contains a pBR322 replicon and a beta-lactamase gene; thus, the cloning of disrupted genomic DNAs from inverse transposition mutants was easily accomplished after ligation of genomic fragments and transformation into E. coli. Thousands of transconjugants could be obtained in a single mating experiment, and inverse transposition was random as demonstrated by Southern hybridization. By this procedure the disrupted genes from P. gingivalis pleiotropic mutants were quickly cloned, sequenced, and identified.

Genetic enhancement of learning and memory in mice

Hebb's rule (1949) states that learning and memory are based on modifications of synaptic strength among neurons that are simultaneously active. This implies that enhanced synaptic coincidence detection would lead to better learning and memory. If the NMDA (N-methyl-D-aspartate) receptor, a synaptic coincidence detector, acts as a graded switch for memory formation, enhanced signal detection by NMDA receptors should enhance learning and memory. Here we show that overexpression of NMDA receptor 2B (NR2B) in the forebrains of transgenic mice leads to enhanced activation of NMDA receptors, facilitating synaptic potentiation in response to stimulation at 10-100 Hz. These mice exhibit superior ability in learning and memory in various behavioural tasks, showing that NR2B is critical in gating the age-dependent threshold for plasticity and memory formation. NMDA-receptor-dependent modifications of synaptic efficacy, therefore, represent a unifying mechanism for associative learning and memory. Our results suggest that genetic enhancement of mental and cognitive attributes such as intelligence and memory in mammals is feasible.

Characterization of the Batl (Bacteroides aerotolerance) operon in Bacteroides fragilis: isolation of a B. fragilis mutant with reduced aerotolerance and impaired growth in in vivo model systems

YT135.2.8, a Tn4400' insertion mutant of Bacteroides fragilis strain TM4000, grows poorly when used to infect Monika or Chinese hamster ovary (CHO) cell monolayers and is outcompeted by wild-type strains in mixed infections. YT135.2.8 also shows defects in the rat granuloma pouch model system in monoculture and is completely outcompeted by the wild-type strain in a mixed infection. In addition, this mutant shows defects in a new model system consisting of CHO suspension cell columns. All of these defects may be explained by the finding that YT135.2.8 shows decreased tolerance to exposure to atmospheric oxygen (less aerotolerant). The monolayer growth defect (MGD) of YT135.2.8 can be influenced significantly by the presence of sulphur-containing reducing agents (cysteine, dithiothreitol, thiodiglycol) or the non-sulphur reducing agent Tris-(2-carboxylethyl)phosphine (TCEP). The defects in YT135.2.8 can be complemented by a 6.6 kb fragment of the B. fragilis chromosome. DNA sequencing of this fragment and of the regions flanking the Tn4400' insertion in the B. fragilis chromosome revealed the presence of five open reading frames, corresponding to genes bat (Bacteroides aerotolerance) A, B, C, D, E, which form the Batl operon; Tn4400' inserted within batD. All of the hypothetical proteins possess one or more membrane-spanning domains. BatA and BatB show high similarity to each other but, like BatD, they show no match to sequences of known function in the databases. BatC and BatE contain 2-4 repeated sequences similar to the tetratricopeptide repeats (TPRs) seen in many eukaryotic proteins. The function of TPR sequences in protein interactions in other systems leads to the suggestion that the Bat proteins form a complex. The Batl complex may be involved in the generation or export of reducing power equivalents to the periplasm of the B. fragilis cell.

Enhanced glial cell line-derived neurotrophic factor mRNA expression upon (-)-deprenyl and melatonin treatments

Glial cell line-derived neurotrophic factor (GDNF) has been shown to be a preferentially selective neurotrophic factor for dopamine (DA) neurons. In the present study, we have examined the distribution of GDNF mRNA expression in several major DA-containing cell body and terminal areas and the regulation of GDNF mRNA expression upon various pharmacological treatments. Results indicated that there is a relatively higher GDNF mRNA level in neurons of the nigrostriatal and mesolimbic dopaminergic pathways. Upon chronic 1-methyl-4-phenyl1,2,3,6-tetrahydropyridine (MPTP) treatment (30 mg/ kg, i.p., for 7 days), DA level was decreased, whereas GDNF mRNA expression was increased in the striatum, suggesting that more GDNF is synthesized and expressed to cope with the neurotoxin insult. Furthermore, among several DA neuron protective and/or therapeutic agents examined, both intrastriatal injections of (-)-deprenyl (1.25 microg and 2.5 microg) and melatonin (30 microg, 60 microg, and 120 microg) significantly enhanced GDNF mRNA expression in the striatum, whereas the same concentrations of (-)-deprenyl did not affect monoamine oxidase B (MAOB) activity, although it increased glutathione peroxidase (GPx) and/or superoxide dismutase (SOD) activities. Similarly, the same concentrations of melatonin did not alter SOD or GPx activities, except that the highest dose of melatonin (120 microg) increased lipid peroxidation in the striatum. Conversely, GM1 ganglioside injection (45 microg) lacked of an effect on GDNF mRNA expression. Together, these results suggest that both (-)-deprenyl and melatonin up-regulate GDNF gene expression at threshold doses lower than that needed for altering MAOB activity and/or the antioxidant enzyme systems, respectively. These results provide new information on the neuroprotective and therapeutic mechanisms of (-)-deprenyl and melatonin on DA neurons.

Expression of integrin-associated protein gene associated with memory formation in rats

The present study has adopted the PCR differential display method to identify cDNA clones associated with memory formation in rats. The one-way inhibitory avoidance learning task was used as the behavioral paradigm. Total RNA isolated from the hippocampus of poor-memory (<80 sec) and good-memory (600 sec) rats 3 hr after training was used for comparison. Three cDNA fragments corresponding to different spliced forms of integrin-associated protein (IAP) mRNA were found to be differentially expressed in the hippocampus of good-memory rats. Quantitative reverse transcription-PCR revealed approximately four fold higher of IAP mRNA level in good-memory rats. This result was confirmed further by in situ hybridization analysis, and the major difference was in the dentate gyrus. It has been demonstrated that this difference in IAP mRNA expression is not attributable to different sensitivities of individual rats to electric shock. Rapid amplification of cDNA ends obtained the full-length IAP cDNA, which is 1192 bp in length excluding the poly(A+) tail. The IAP mRNA expression was significantly upregulated by NMDA and amphetamine injections to the dentate gyrus of the hippocampus. On the other hand, injection of antisense oligonucleotide complementary to the IAP transcript markedly impaired memory retention in rats and decreased the amplitude and slope of EPSP in the in vivo long-term potentiation paradigm. These results together suggest that IAP gene expression plays an important role in memory formation and synaptic plasticity in rat hippocampus.

A concussive-like brain injury model in mice (II): selective neuronal loss in the cortex and hippocampus

A novel concussive-like brain injury (CLBI) model characterized by transient neurobehavioral depression, short duration of brain edema, and long-lasting memory deficits has been reported in our companion paper. This was achieved by dropping a 21-g weight from a height of 25 cm onto the head of a mouse. In the present study, we examined the histopathological changes in this model. Male ddY mice were subjected to either the trauma or sham injury. Gross pathological examination of the brain 1 h posttrauma did not demonstrate subdural, subarachnoid, intraventricular, periventricular, and intraparenchymatous hemorrhage, focal lesions or contusions. Microscopic examination 24 h posttrauma with Nissl staining (cresyl violet), however, revealed a selective bilateral neuronal cell loss in the cerebral cortex and hippocampus but not in the regions of the thalamus, cerebellum, and brain stem. The characteristics of neuronal cell loss in the cortex suggested that this pathology was related in part, to the head impact dynamics, since the cell loss was noted in the central portion of the supraventricular cerebral cortex (p < 0.001), the site of the weight impact, gradually decreasing peripheral to this site, and disappearing in the areas remote from this locus. In contrast, neuronal cell loss seen in the hippocampus did not suggest that this pathology was directly associated with the impact site. Neuronal cell loss was concentrated in the pyramidal cell layer of CA2 (p < 0.01) and CA3 (p < 0.01), and a lesser degree was noted in the subfields of CA3c (p < 0.05) and the hilar region (p < 0.05) but not in the subfields of CA1 and the dentate gyrus layers. The present study characterized the histopathological change seen in the CLBI model, demonstrating the selective neuronal cell loss following weight-drop concussion in mice.

A concussive-like brain injury model in mice (I): impairment in learning and memory

The modeling of human concussive brain injury (CBI) in the laboratory has been challenging. In the present study, we developed an experimental CBI model in mice using a novel weight-drop device. Various injury levels were examined by adjusting the height of the falling weight (diameter 10 mm, length 20 cm, weight 21 g). At a height of 50 cm, the impact resulted in a mortality rate of 46.7% with a skull fracture rate of 28.6%. At a height of 25 cm, however, the impact produced a concussive-like brain injury (CLBI) to the mice without skull fracture. A series of pathophysiological and neurobehavioral responses was evaluated at this injury level. The CLBI mice lost muscle tone and righting reflex response immediately following the trauma and recovered from the latter within a short duration of 1.6 +/- 0.32 min (mean +/- SE). Brain edema formation started at 12 h, reached a maximum at 24 h and recovered 48 h. Typically edema was found in the neocortex, hippocampus, and cerebellum, but not in the brain stem. Deficits in the feeding behaviors lasted for 2 days, accompanied by lower body weight persisting for 5 days. The body weight growth rate for 24 h returned to the control levels by the third day postinjury. Learning and memory were evaluated at the end of 1-3 weeks after the trauma using a water-finding task. At 1 week, exploratory behaviors were slightly inhibited while learning and memory were profoundly impaired. Interestingly, the learning and memory deficits lasted for 2 weeks while recovering to the control levels by 3 weeks. No motor disability was found in the CLBI mice during the 3-week evaluations. These results indicate that the weight-drop impact produced graded injury to the brain, and at the injury level of 25 cm it produced a CLBI in the mice in which the characteristics of transient loss of neurobehavioral responses, short duration of brain edema, and long-lasting learning and memory deficits are similar to those of human CBI.

Brain region-specific regulation of luteinizing hormone-releasing hormone messenger ribonucleic acid in the male ferret: interactions between pubertal maturation and testosterone

This study examined the regulation of LHRH messenger RNA (mRNA) during pubertal maturation and by testosterone in male ferrets. Prepubertal and postpubertal ferrets were either intact or were castrated and treated with daily injections of oil or 5 mg/kg testosterone propionate for 14 days. In situ hybridization for LHRH mRNA was performed using an 35S-labeled 48-base oligonucleotide complementary to the human LHRH-coding region. Computerized image analysis was performed on cells in the preoptic area, retrochiasmatic area, arcuate nucleus (ARC), and median eminence; cells were classified as labeled if the number of pixels representing silver grains over the cell was 5 or more times the number of background silver grain pixels. Both pubertal maturation of intact males and castration of prepubertal males resulted in an increase in the number of labeled cells in the ARC. These effects were not observed in any of the other three brain regions, suggesting that ARC LHRH-producing neurons are of primary importance in the presumed increase in LHRH release that occurs as a consequence of either pubertal maturation or castration of prepubertal males. Castration of adults did not increase the number of labeled cells in any brain area, but resulted in an increase in silver grains per labeled cell only in the preoptic area. Thus, LHRH mRNA is regulated during puberty primarily in the ARC, and the particular cell group in which LHRH mRNA is most strongly regulated by testosterone changes with pubertal maturation.

Effects of VA-045 on learning and memory deficits in traumatic brain injury (TBI)-induced retrograde and anterograde amnesic mice

1. No specific regimen has been developed to treat post-traumatic amnesia in man. In the present study, we examined the effects of (+)-eburnamenine-14-carboxylic acid (2-nitroxyethyl) ester (VA-045), a novel derivative of apovincaminic acid, on learning and memory deficits associated with a mild traumatic brain injury (TBI) in mice. 2. Two kinds of amnesia, TBI-induced retrograde amnesia (TRA) and anterograde amnesia (TAA), were produced by means of post- and pre-acquisition head injury, respectively, by a simple weight-drop device. A novel procedure of water-finding task was used to assess learning and memory functions. 3. Both TRA and TAA mice were dramatically impaired in the task performance, with prolonged latencies for finding and drinking in either retention test or retest, indicating that retention was impaired in TRA mice while learning and retention were impaired in TAA mice. 4. VA-045 administered 30 min post-trauma in TRA mice dramatically shortened the prolonged latencies for finding and drinking in both retention test and retest, indicating that VA-045 significantly improved the retention deficit observed in TRA mice. 5. VA-045 administered 30 min post-trauma in TAA mice dramatically attenuated the prolonged latencies for finding and drinking in both retention test and retest, indicating that VA-045 significantly improved the learning and retention deficits observed in TAA mice. 6. Administration of VA-045 30 min pre-trauma in normal mice markedly attenuated the delay of latencies for finding and drinking after trauma in both retention test and retest, which shows that VA-045 significantly prevented learning and retention deficits after TBI. 7. Motor activities were not significantly affected by either the TBI or the chemical treatment at the time of task examination in either experimental model. 8. It is concluded that VA-045 may have potential effects on learning and memory deficits observed in either TBI-induced retrograde or anterograde amnesia.

Involvement of activation of dopaminergic neuronal system in learning and memory deficits associated with experimental mild traumatic brain injury

Much evidence has indicated that a disturbance in dopamine neurotransmission following mild to moderate traumatic brain injury is involved in the development of post traumatic memory deficits. In the present study we examined the effects of a dopamine receptor agonist and some antagonists on latent learning and memory deficits associated with a concussive traumatic brain injury in mice. Anaesthetized animals were subjected to mild traumatic brain injury by dropping a weight onto the head, and a single-dose injection of apomorphine (0.3-3.0 mg/kg) or haloperidol (0.3-3.0 mg/kg) was made i.p. 15 min after the trauma. One week later, a water-finding task consisting of an acquisition trial, a retention test and a retest was employed to assess learning and memory functions. Mice that had received a traumatic brain injury were impaired in task performance, with prolonged latencies for finding and drinking in the retention test and retest. Administration of haloperidol but not of apomorphine significantly shortened the prolonged latency in both of the tests, indicating that antagonism of dopamine receptors is beneficial for the recovery of post traumatic memory deficits. In order to evaluate which receptor subtype plays the major role in this model, we examined the effects of SCH-23390 (0.03-0.3 mg/kg), a D1 receptor antagonist, and sulpiride (3.0-30 mg/kg), a D2 receptor antagonist, in the same experimental paradigm. The results showed that administration of sulpiride but not of SCH-23390 significantly improved the deficits in task performance, indicating that D2 receptors are the major site of action. However, combined treatment with SCH-23390 (0.03-0.3 mg/kg) and sulpiride (3.0 mg/kg) at doses that had no effect when the antagonists were given alone exerted a significant additive effect in improving these deficits, indicating that interaction between D1 and D2 receptors is involved in these processes. The present results suggest that a dopaminergic mechanism contributes to the memory dysfunction associated with traumatic brain injury.

NGFI-B, c-fos, and c-jun mRNA expression in mouse brain after acute carbon monoxide intoxication

The expression of immediate early genes (IEG) has been documented in the brain after various kinds of insults such as ischemia and hypoxia. To determine whether acute carbon monoxide intoxication (ACOI) might trigger IEG expression, adult ddY mice were subjected to carbon monoxide exposure at a rate of 30 mL/min for 35 seconds. The levels of NGFI-B, c-fos, and c-jun mRNA were determined by Northern blot analysis. A time-course study in the cerebral cortex indicated that the induction of NGFI-B, c-fos, and c-jun mRNA started as early as 15 minutes, reached a peak at 30 minutes, and returned to the basal level at 1 hour after the ACOI. In addition, the temporal feature of the induction of these IEG mRNA in the hippocampus was very similar to that in the cerebral cortex. Examination of brain regions at 30 minutes after the ACOI revealed a significant induction of NGFI-B mRNA in the cerebellum, thalamus-hypothalamus, brainstem. as well as in the cortex and hippocampus, but not in the striatum or olfactory bulb. Furthermore, the neuroanatomical distribution of c-fos mRNA at 30 minutes after the ACOI was very similar to that of the NGFI-B mRNA. The widespread distribution of these IEG in the brain, especially in the cerebellum and brainstem, indicates that the major cause for the triggering of IEG expression in the brain by the ACOI might be a diffuse hypoxia. These findings show for the first time the temporal and spatial expression of IEG in the brain after ACOI.

(+)-Eburnamenine-14-carboxylic acid (2-nitroxyethyl) ester (VA-045), a putative cognitive enhancer, facilitates recovery from concussive brain injury-induced learning and memory impairments in mice

We characterized alterations in the ability of concussive brain injury (CBI) models to perform a water-finding task and examined effects of (+)-eburnamenine-14-carboxylic acid (2-nitroxyethyl) ester (VA-045), a novel apovincaminic acid derivative, on post-traumatic impairments in latent learning and memory processes. Two types of CBI-induced amnesia (retrograde and anterograde) were produced by means of post- or preacquisition head impact using a simple weight-drop device. Profound impairments of latent learning and memory processes related to retention and retrieval were observed in the CBI mice. In the CBI-induced retrograde amnesia model, VA-045 (0.5-4.0 mg/kg) significantly ameliorated impairments of latent learning and retention in both the retention test and the retest. In the CBI-induced anterograde amnesia model, the protective effects of the compound on impairments in latent learning and retention or retrieval were significant in both the retention test and the retest. These results suggested that VA-045 may be a novel cognitive enhancer for attenuating or protecting against the learning and memory dysfunction associated with CBI.

A synergistic interaction between dopamine D1 and D2 receptor subtypes in the memory impairments induced by concussive brain injury (CBI) in mice

Profound latent learning and memory deficits with increased monoamine levels in the brain following concussive brain injury (CBI) have been documented in our previous work. The purpose of the present study was to determine the role of dopamine (DA) receptor subtypes in the memory deficits associated with CBI. Profound latent learning and memory impairments were observed in the vehicle-treated CBI mice. SCH-23390 administered 15 min post-injury had no significant effects on the impairments of latent learning and memory in the CBI mice. Sulpiride significantly improved the impairments of latent learning and memory in a dose-dependent manner, indicating that activation of dopaminergic neuronal function is involved in the CBI-induced amnesia. Interestingly, co-administration of sulpiride and SCH-23390, at doses which alone has no significant effect, significantly ameliorated the impairments of latent learning and memory. These results strongly suggested that D1 and D2 receptor subtypes are synergistically involved in the dysfunction of learning and memory associated with CBI.

Photoperiod modulates pubertal shifts in behavioral responsiveness to testosterone

This study examined the effect of photoperiod on pubertal maturation of steroid-dependent reproductive behaviors in male European ferrets (Mustela putorius furo). In the first experiment, levels of neck gripping, mounting, and pelvic thrusting in gonadally intact prepubertal (PRE) ferrets were compared with those of adults that had undergone puberty either while housed in short days (8 hr light/16 hr darkness per day; SD), or after transfer from SD to long days (18 hr light/6 hr darkness per day; LD) at 12 weeks of age. Both LD and SD adults demonstrated significantly greater amounts of neck gripping and mounting than PRE males. In addition, a significantly greater proportion of adults in both SD and LD displayed at least one incidence of the three behaviors compared to PRE ferrets. There were no statistically significant differences in behavior of the gonadally intact LD and SD adults. In the second experiment, dose-response curves for behavioral responses to subcutaneous injections of 0, 0.5, 1.25, 2.5, 5, and 10 mg/kg testosterone propionate (TP) in oil were generated in castrated PRE, SD, and LD males. The lowest dose of TP elicited significantly greater amounts of all three behaviors in LD adults than in PRE ferrets. In addition, levels of mounting and thrusting elicited by the lowest dose of TP were significantly greater in LD adults than in SD adults. These data indicate that pubertal activation of male sexual behavior in male ferrets is accompanied by a pubertal increase in responsiveness to the behavioral effects of testosterone. Furthermore, the degree of behavioral responsiveness of adult ferrets to testosterone is modulated by environmental photoperiod experienced during reproductive maturation.

LHRH in the ferret: pubertal decrease in the number of immunopositive arcuate neurons

This study correlated a region-specific change in the number of luteinizing hormone-releasing hormone-immunopositive (LHRH+) neurons with pubertal development in male ferrets. There were 50% fewer LHRH+ cell bodies in the arcuate nucleus of peri- and postpubertal ferrets than in prepubertal ferrets; this significant decrease represented a 15% reduction in the overall number of LHRH+ neurons. Intracerebroventricular colchicine did not reveal additional numbers of LHRH+ neurons in the arcuate nucleus, indicating that the pubertal decrease in arcuate LHRH+ cell bodies was not due to rapid transport of peptide. These results suggest that LHRH of arcuate origin may inhibit release of LHRH via ultrashortloop negative feedback in prepubertal ferrets. Cessation of peptide production in half of the arcuate LHRH neurons at puberty could result in a reduction in this inhibitory signal that permits the pubertal increase in LHRH/LH release. Alternatively, LHRH of arcuate origin may have a nonpituitary role. In either case, these data provide evidence for heterogeneity of function among LHRH+ neurons.

Testosterone in MPOA elicits behavioral but not neuroendocrine responses in ferrets

The amount of time male ferrets were engaged in neck gripping, mounting, and thrusting was quantified in 30-min tests with a receptive female before and after castration. Bilateral cannulae containing a total of approximately 2 mg testosterone propionate (TP) in cocoa butter were then stereotaxically aimed at the medial preoptic area (MPOA). Tests for sexual behavior were conducted on days 3, 7, 14, and 21 postimplantation. Ferrets were histologically categorized as either 1) Miss (implants not in MPOA), 2) Unilateral implant in MPOA, or 3) Bilateral implants in MPOA. The mean amount of time spent neck gripping, mounting, and thrusting increased significantly over castrate levels on postimplantation day 14 in the Bilateral group, but not in the Miss or Unilateral groups. In all groups, mean plasma testosterone concentrations were below or near the lower limit of detectability on the day before TP implantation and on postimplantation test days. In the same plasma samples, luteinizing hormone concentrations were within the normal range of castrated ferrets, and did not significantly decline after TP implantation. These results suggest that the MPOA is a neural site for androgen activation of certain components of reproductive behavior but not for negative feedback on gonadotropin secretion in male ferrets.

Differential effects of testosterone, 5 alpha-dihydrotestosterone and oestradiol-17 beta on plasma concentrations of LH in castrated ferrets

The biological activity of testosterone often depends on the conversion of testosterone within the target cell to an androgenic or oestrogenic metabolite. The purpose of this study was to compare the relative ability of testosterone and two of its metabolites, dihydrotestosterone (DHT) and oestradiol, to suppress LH secretion in castrated male ferrets. Castrated ferrets were treated with five different doses of steroid by implanting various numbers of s.c. silicone elastomer capsules packed with either testosterone, DHT or oestradiol. The lowest dose of oestradiol (0.1 mm capsule length/100 g body weight, mean estimated total release rate of 25 ng/day) significantly suppressed plasma concentrations of LH in castrated ferrets. Higher amounts of DHT (2.5 mm capsule length/100 g body weight, mean estimated total release rate of 88 ng/day) were required for a significant reduction in plasma concentrations of LH. Concentrations of LH were also significantly lowered by testosterone when administered at a 2.5 mm capsule length/100 g body weight; however, estimated total release rate was 312 ng/day from these capsules. The fact that oestradiol was more effective than DHT, and that DHT was more effective than testosterone in inhibiting LH secretion in castrated ferrets, suggests that in gonadally intact ferrets, testosterone may be converted to DHT or oestradiol within target cells that mediate steroid negative feedback on LH secretion.

Gabaergic interneurons in the dorsal raphe mediate the effects of apomorphine on serotonergic system

Apomorphine (APO) has been shown to elevate the concentrations of serotonin (5-HT) and its major metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the mesostriatal but not the mesolimbic serotonergic systems. We have previously demonstrated that the serotonergic actions of APO were secondary to dopamine (DA) autoreceptor stimulation in the substantia nigra. Using picrotoxin as a pharmacological tool, we have presently found that these effects of APO were also indirectly mediated through gamma-aminobutyric acid (GABA) neurons. In examination of the exact anatomical locus of GABA neurons responsible for the observed effects of APO, the results indicate that bilateral lateral habenular lesions did not block the effects of APO on 5-HT neurons, while direct picrotoxin infusion to the dorsal raphe, at a dose having no significant influence by itself, antagonized APO's actions. Together with the anatomical, biochemical and histofluorescent findings, it is suggested that APO influences dorsal raphe 5-HT by stimulation of DA autoreceptors in the substantia nigra; therefore, inhibition of DA neuron activity and the nigro-raphe pathway. Normally, DA probably exerts an excitatory influence on gabaergic interneurons in the dorsal raphe, and these inhibitory interneurons then synapse on 5-HT neurons in the same area. Activation of 5-HT neurons were explained by a disinhibitory effect as a result of reduced release of GABA due to feedback inhibition of DA neuron firing following APO activation of DA autoreceptors in the substantia nigra. The striatal presynaptic and postsynaptic DA receptors, however, do not appear to mediate the above effects of APO.

Differential biochemical mechanisms mediate locomotor stimulation effects by caffeine and nicotine in rats

Effects of caffeine and the interactive effects of caffeine and nicotine on locomotor activity in rats were examined in the present study. Other than confirming previous reports that both drugs enhanced locomotion, we have also found that their effects on activity were additive. Meanwhile, results of various biochemical measures have revealed that at the minimum effective doses of caffeine and nicotine which facilitated locomotor activity, only one biochemical system was preferentially influenced by either drug alone. The most significant findings were that caffeine stimulated the release of catecholamines and nicotine decreased the concentrations of tyrosine and tryptophan in brain. The combined effects of caffeine and nicotine on these brain amines were not different from those of each drug alone. Together with the report that caffeine and nicotine had differential actions on different activity measures, the present results support the hypothesis that caffeine and nicotine affect locomotor activity via different neurochemical mechanisms.

Stress and corticotropin-releasing factor potentiate center region activity of mice in an open field

The effects of corticotropin-releasing factor (CRF) and previously published effect of stress on the locomotor activity of mice in different regions of an open field were compared. Intracerebroventricular (ICV) administration of 0.2 microgram CRF, like stress, significantly increased center region activity; this effect was reversed by the benzodiazepine diazepam (DZP) at a dose of DZP having no significant effect alone. A dose of DZP that antagonized CRF-potentiated center region activity did not block amphetamine-stimulated center area activity. These results suggest that CRF may normally be responsible for many behavioral changes during conditions of stress.