Koichi Tsunashima

Multiple-time replicability of near-infrared spectroscopy recording during prefrontal activation task in healthy men

Near-infrared spectroscopy (NIRS) has the potential for clinical application in neuropsychiatry because it enables non-invasive and convenient measurement of hemodynamic response to cognitive activation. Using 24-channel NIRS in 12 healthy men, we examined the replicability of oxy- and deoxy-hemoglobin concentration ([oxyHb], [deoxyHb]) changes in the prefrontal cortex during the category fluency task over four repeated sessions (each 1-week apart). Multiple methods were employed to evaluate the replicability of magnitude, location, and time course of the NIRS signals ([oxyHb], [deoxyHb]). Task performances did not differ significantly across sessions, nor were they significantly correlated with NIRS signals. Repeated measures ANOVA and variance component analysis indicated high replicability of magnitude for both NIRS measures, whereas the effect sizes of between-session differences in [oxyHb] were not negligible. The number and spatial location of significantly activated channels were sufficiently replicable for both measures, except that the across-session overlap of significantly activated channels was weak in [deoxyHb]. The time course of the activation was acceptably replicable in both measures. Taken together, these findings suggest there is considerable replicability of multiple-time measurements of prefrontal hemodynamics during cognitive activation in men. Further studies using different conditions or assessing sensitivity to longitudinal changes following interventions are necessary.

Cytokines participate in neuronal death induced by trimethyltin in the rat hippocampus via type II glucocorticoid receptors.

We investigated the role of IL-1alpha and IL-1beta expressed in the reactive gliosis following hippocampal damage induced by trimethyltin (TMT). IL-1alpha immunoreactivity was expressed earlier in small glial cells on day 4 post-TMT, while IL-1beta expression was obvious in large swollen glial cells on day 14 post-TMT. Both IL-1alpha and IL-1beta immunoreactivities were double-labeled with astrocyte marker, vimentin, but not with a microglia marker, OX-42. The expression of both IL-1alpha/beta was enhanced by adrenalectomy (ADX) prior to TMT administration. Corticosterone (CORT) or dexamethasone (DEX) supplementation not only cancelled effects of ADX, but also partially reversed TMT-induced enhancement of IL-1alpha/beta expressions. These changes coincided with TMT-induced neuronal death in CA3 pyramidal cells of the hippocampus. It is suggested that IL-1alpha/beta expressed in reactive astrocytes participate in TMT neurotoxicity via type II glucocorticoid receptors.

Scratching behavior induced by bombesin-related peptides. Comparison of bombesin, gastrin-releasing peptide and phyllolitorins

Bombesin and 10 bombesin-related peptides were administered intracerebroventricularly to conscious and freely moving rats. All peptides tested were found to elicit excessive grooming, especially scratching behavior. Bombesin itself had the most potent and long-lasting activity in eliciting scratching behavior. Naturally occurring peptides such as neuromedin B and gastrin-releasing peptide (GRP)-(18-27) were short-acting compared with exogenous peptides such as bombesin and synthesized analogs. Two phyllolitorins, a new bombesin subfamily, were also examined in this study. [Leu8]phyllolitorin induced more scratching than [Phe8]phyllolitorin and proved to be virtually equipotent to bombesin. Corticotropin-releasing factor (CRF) and substance P induced considerable excessive grooming, but both peptides were strikingly weak in inducing scratching behavior. It is suggested that (1) scratching represents a specific behavior commonly induced by bombesin-related peptides and (2) the relative potency to induce scratching behavior reflects the metabolic stability of the peptide, e.g. endogenous versus exogenous, shorter versus longer sequences, or chemical protection of N-terminus.

Association of morphine-induced antinociception with variations in the 5'flanking and 3' untranslated regions of the μ opioid receptor gene in 10 inbred mouse strains

Objective Genetic factors are hypothesized to be involved in interindividual differences in opioid sensitivity. Inbred mouse strains that are genetically different and isogenic within each strain are useful for elucidating the genetic mechanisms underlying the interindividual differences in opioid-induced analgesia. Methods We examined the effects of morphine in 10 inbred mouse strains, including wild-derived strains that have a wide range of genetic diversity, including BLG2, CHD, KJR, MSM, NJL, PGN2, and SWN. We also performed full sequencing of the 5′ flanking region and exons of the mouse μ opioid receptor gene Oprm1 and analyzed the association between genotypes and phenotypes in these mice. Results The effects of morphine on locomotor activation and antinociception varied among the inbred strains. The nucleotide differences that cause amino acid substitutions were not found in the Oprm1 gene in the inbred strains analyzed in this study. In the 5′ flanking region and 3′ untranslated region of the Oprm1 gene, four highly variable regions containing novel short tandem repeat polymorphisms (GA, T, TA, and CA/CT) were identified. The GA, T, and TA repeat numbers were significantly associated with morphine-induced antinociception. Conclusion These results suggest that the short tandem repeats in the 5′ flanking and 3′ untranslated regions of the μ opioid receptor gene are involved in interstrain differences in opioid sensitivity in mice. Wild-derived inbred mouse strains with different numbers of these repeats may be useful models for examining interindividual differences in opioid sensitivity.

Neuropeptide Y and somatostatin participate differently in the seizure-generating mechanisms following trimethyltin-induced hippocampal damage

Trimethyltin (TMT) is an organic metal known to induce neuronal degeneration in the hippocampus, and abnormal behavior characterized by seizures, increased aggression and memory deficits. We administered TMT to rats and studied the changes of neuropeptide Y (NPY) and somatostatin (SOM) in the hippocampus. Phenobarbital (PB) was administered as an anticonvulsant to assess the effect of seizures on neuropeptide expressions in both dorsal and ventral hippocampus. Histochemically, NPY-immunoreactivity increased 4 days after TMT treatment in the hilus of the hippocampus, then progressively decreased and dropped to a level below control 16 days after TMT treatment. Detection of NPY mRNA by in situ hybridization preceded the detection of NPY by immunohistochemistry. NPY mRNA signals increased in the hilus 2 days after TMT treatment. SOM-immunoreactivity also increased in the hilus of the hippocampus 2 days after TMT treatment, then decreased rapidly to a normal level. Similar changes in SOM mRNA were demonstrated by in situ hybridization. PB treatment significantly inhibited changes of NPY in terms of both immunoreactivity and mRNA expression; however, the same treatment failed to affect changes in SOM expression. This suggests that NPY and SOM act by different mechanisms in TMT-induced neurodegeneration.

Temporal change of hippocampal enkephalin and dynorphin mRNA following trimethyltin intoxication in rats: effect of anticonvulsant

Trimethyltin (TMT), an organic metal, has been known to induce behavioral abnormalities including seizures and aggression. We administered TMT to rats, then, behavioral changes as well as the changes of dynorphin and Met-enkephalin mRNA were observed with or without phenobarbital treatment in order to reveal the role of neuropeptides in seizure-generating mechanisms. Met-enkephalin mRNA was significantly increased at the 2nd to 6th day after TMT administration when seizure was frequently observed. Meanwhile, dynorphin mRNA was decreased significantly from the 2nd day to 16th day during aggression score remained high. Phenobarbital abolished not only seizures and aggression, but also the changes of neuropeptide expressions. These results suggest that the changes of dynorphin mRNA are more strongly associated with aggression than seizures, while Met-enkephalin changes correlate more with seizures.

Symptom classification of schizophrenia changes with the duration of Illness

Our starting hypothesis was that schizophrenic symptomatology changes over time. This hypothesis explains conflicting reports 011 schizophrenic symptom structures as a consequence of different durations of illness in the samples studied to date. Therefore a sample of ‘258 schizophrenic in‐patients (with ICD‐10 diagnoses F20) was categorized according to illness duration. A factor analysis was performed on the 8 items of the Manchester Scale for three subgroups (duration < 10 years, 10‐20 years and ≥ 20 years). For those patients whose illness duration was less than 10 years, ‘formal thought disorder’ was not related to any other mental state, whereas for those whose duration was 10 years or longer, it was correlated with ‘negative symptoms’. In the < 10 years group, ‘anxiety and depression syndrome’ and ‘positive symptoms’ formed one complex, but these symptoms were separated into two distinct syndromes in the ≥20 years group. Thus we were able to demonstrate that the classification of symptoms changes with increasing duration of illness.

Expression of fos protein in rat brain following administration of a nicotinic acetylcholine receptor agonist epibatidine.

Epibatidine (exo-2-(6-chloro-3-pyridyl)-7-azabicyclo-[2.2.1]heptane), an extract of frog skin, is a novel and highly potent agonist for the nicotinic acetylcholine (ACh) receptor. The present study was undertaken to examine the expression of Fos protein in several rat brain regions following an acute administration of epibatidine. Furthermore, we also studied the role of the dopamine D1 and D2 receptors and the N-methyl-d-aspartate (NMDA) receptor, and nicotinic ACh receptor in the expression of Fos protein by epibatidine. A single administration of epibatidine (5, 10, 50 microgram/kg) caused a marked induction of Fos-immunoreactivity in the prefrontal cortex, medial striatum, nucleus accumbens, amygdala and superior colliculus of rat brain. In these regions, pretreatment with SCH 23390 (1.0 mg/kg), a dopamine D1 receptor antagonist, MK-801 (1.0 mg/kg), a NMDA receptor antagonist, and mecamylamine (5. 0 mg/kg), a nicotinic Ach receptor antagonist, inhibited the induction of Fos protein by epibatidine (10 microgram/kg). Pretreatment with sulpiride, a dopamine D2 receptor antagonist, blocked the induction of Fos protein in the prefrontal cortex and the core region of accumbens nucleus, but not in the medial striatum and the shell division of nucleus accumbens of rat brain. These results suggest that epibatidine induced the expression of Fos protein in several regions of rat brain, and that dopamine D1 receptor, NMDA receptor, and nicotinic ACh receptor may play a role in the expression of Fos protein by epibatidine in rat brain. Furthermore, dopamine D2 receptor may, in part, play a role in epibatidine induced expression of Fos protein in the prefrontal cortex and the core region of nucleus accumbens, but not in the medial striatum and the shell division of nucleus accumbens of rat brain.

Increased expression of zif268 mRNA in rat retrosplenial cortex following administration of phencyclidine

Phencyclidine (PCP) has been shown to cause neurotoxicity in rat retrosplenial cortex following a single administration, although the precise mechanism underlying PCP-induced neurotoxicity is unclear. Using in situ hybridization and immunohistochemistry, we studied the effects of PCP on expression of immediate early gene zif268 mRNA and zif268 protein in the rat brain. High constitutive levels of zif268 mRNA and zif268 immunoreactivity were observed in the brain of control rats. Administration of PCP (12.5, 25 or 50 mg/kg, i.p., 6 h) caused marked induction of zif268 mRNA in the rat retrosplenial cortex, in a dose-dependent manner. However, the basal levels of zif268 mRNA in the other regions of cerebral cortex were decreased by administration of PCP. Emulsion-autoradiographical study suggested that marked expression of zif268 mRNA was observed in the layers III and IV of retrosplenial cortex where the neurotoxicity of PCP was detected. Furthermore, zif268 immunoreactivity in the layer IV of retrosplenial cortex was not changed by administration of PCP (25 mg/kg, i.p., 5 h), but that in the other layers of retrosplenial cortex was reduced by PCP. These results suggest that immediate early gene zif268 may, in part, play a role in the neurotoxicity of NMDA receptor antagonists such as PCP.

The effect of delta sleep-inducing peptide (DSIP) on the changes of body (core) temperature induced by serotonergic agonists in rats

Hyperthermia induced by high doses of 5-methoxy-N,N-dimethyl-tryptamine (5-MeODMT) was diminished and hypothermia induced by low doses of 5-MeODMT was enhanced by pretreatment with delta sleep-inducing peptide (DSIP). Delta sleep-inducing peptide had an enhancing effect of hypothermia induced by 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT). This action of DSIP was completely inhibited by ICV injection of anti-DSIP. Pindolol prevented the enhancing action of DSIP on both 8-OH-DPAT- and apomorphine-induced hypothermia. It is suggested that the thermoregulatory action of DSIP is primarily exerted by a 5-HT1A mechanism in the rat.