Hiromichi Hashimoto

Biorhythm of arginine-vasopressin in the paraventricular, supraoptic and suprachiasmatic nuclei of rats

The diurnal variations in content of arginine-vasopressin in the supraoptic nucleus, the paraventricular nucleus and the suprachiasmatic nucleus of rats were determined using radioimmunoassay. In the supraoptic nucleus and the paraventricular nucleus the arginine-vasopressin level was relatively constant during the light phase (the inactive phase). When it became dark, the level of arginine-vasopressin lowered during the early and middle dark phase and then increased to the highest level during the late dark phase. In the suprachiasmatic nucleus the level was stable during the light phase, while in the early and the late dark phase it was significantly higher than that in the middle dark phase.

Spontaneous Release of γ‐Aminobutyric Acid Formed from Putrescine and Its Enhanced Ca2+‐Dependent Release by High K+ Stimulation in the Brains of Freely Moving Rats

The spontaneous release of [3H]γ‐aminobutyric acid ([3H]GABA) in various areas of rat brain in jected with [3H]putrescine was examined using a push pull perfusion technique. The release in a 25‐min perfusate was highest in the caudate‐putamen. The effect of high K+ stimulation on the release of [3H]GABA formed from [3H]putrescine was examined in the caudate‐putamen. The release was enhanced by high K+ solution in a Ca2+‐dependent manner.

Effects of L-Threo- and erythro-3,4-dihydroxyphenylserine on learning performance and concentrations of brain noradrenaline and its metabolites in rats

Effects of L-threo and L-erythro-3,4-dihydroxyphenylserine [DOPS, precursor amino acids for noradrenaline (NA)] on the learning performance in a maze paradigm designed to model on the water maze paradigm using a multicomputerized behavioral analysis system were studied. A marked facilitation of learning performance was observed in rats after an intraventricular injection of 5 micrograms L-threo-DOPS (the s-NA precursor), and this effect was inhibited by a simultaneous administration of 1 or 2 micrograms propranolol (a beta-adrenergic antagonist). As concentrations of brain NA, 3-methoxy-4-hydroxyphenylglycol, and normethanephrine were increased by the injection of 5 micrograms L-threo-DOPS, the effect seemed to be derived from activation of beta-adrenoceptors in the CNS by the formed s-NA. On the other hand, an intraventricular injection of 5 micrograms L-erythro-DOPS (the r-NA precursor) attenuated the learning performance, and this effect was probably caused by the formed r-NA from L-erythro-DOPS.

The Syndrome of Self‐Induced Water Intoxication in Psychiatric Patients

Abstract: This is a report on six psychiatric patients who indulged in excessive ingestion of water and subsequently developed tonic‐clonic seizures in the course of the underlying mental disorders. On the basis of the DSM‐III criteria, they were diagnosed as follows: schizophrenic disorder, 4; schizoaffective disorder, 1; borderline personality disorder, 1. The levels of serum electrolytes were estimated during five episodes of seizures in three patients. Hyponatremia was a consistent finding (serum sodium: mean = 120.6 mEq/liter). Plasma osmolality and plasma levels of arginine vasopressin (AVP) were determined during two episodes in two patients. The inappropriately high circulating levels of AVP relative to plasma hypoosmolality were documented. However, the response to the overnight fluid deprivation and acute water load during the period of no seizures in two patients revealed no evidence of the persistent SIADH, suggesting the temporal association of hyponatremic encephalopathy with inappropriate AVP secretion. It is not conclusive whether the transient SIADH is the cause or the consequence of hyponatremic encephalopathy, although a delusion or an auditory hallucination could play a critical role in drinking water excessively in three patients.

Determination of putrescine in brain tissue using gas chromatography-mass spectrometry

We used gas chromatography-mass spectrometry to assay putrescine in minute regions of single rat brains. Acid extraction, partial purification on Amberlite CG 120, and derivatization with pentafluoropropionic anhydride preceded the gas chromatography-mass spectrometry. A moving-needle solventless system and a direct inlet system were also used to increase sensitivity. Putrescine was measured accurately at the picomole level; the mean concentration of this polyamine in five regions of rat brain found by this method was 2.7-3.8 times higher than reported by other researchers.

Distribution of Putrescine in Rat Brain Measured by Gas Chromatography‐Mass Spectrometry

Abstract: We measured putrescine levels in minute sites of single rat brains using a sensitive, specific assay involving gas chromatography‐mass spectrometry. The putrescine level was measured in 20 sites of single rat brains: three sites in the cerebral cortex, six sites in the hypothalamus, three sites in the basal ganglia, three sites in the thalamus, three sites in the limbic system, and two sites in the cerebellum. The level of putrescine was very high in the hypothalamus, high in the basal ganglia and limbic system, and low in the thalamus, cerebellum, and two of the three sites in the cerebral cortex. The highest levels were in the anterior hypothalamic area and the lateral hypothalamic area, and the lowest levels were in the vermis and the lobe of the cerebellum.

Effect of DL-erythro-dihydroxyphenylserine on the locomotor activity of the mouse

Effect of dihydroxyphenylserine (DOPS) on the locomotor activity of mice pretreated with beta-phenylisopropylhydrazine was studied using an Animex activity meter. An intraperitoneal injection of DL-erythro-DOPS (200 mg/kg) suppressed significantly the locomotor stimulation by the MAO inhibitor, while DL-threo-DOPS (200 mg/kg) had no effect. Only slight suppression was observed after the administration of 100 mg/kg of DL-erythro-DOPS. Effect of DOPS on the concentrations of brain catecholamines and serotonin of mice pretreated with the MAO inhibitor was also analysed. The administration of DL-erythro-DOPS significantly increased the concentration of noradrenaline, while DL-threo-DOPS did not affect the contents of brain amines in the experimental condition. The suppressive effect of DL-erythro-DOPS on the locomotor stimulation by the MAO inhibitor was confirmed by a simultaneous administration of the amino acid and d-phenylisopropylmethylamine to mice. Based on these findings, the neural mechanisms of the locomotor activity and a clinical application of DL-erythro-DOPS to the manic syndrome were discussed.

Effects of prostaglandin E2 and D2 on the release of vasopressin and oxytocin

The effects of prostaglandin (PG) E2 and D2 on the plasma levels of arginine-vasopressin (AVP) and oxytocin (OXT) in rabbits, and on the release of the both hormones from the isolated posterior pituitary of rats were examined. An intraventricular administration of PGE2 to a rabbit raised the plasma levels of the both hormones. An intraventricular injection of PGD2 also increased the plasma level of OXT but not that of AVP. The release of AVP and OXT from fragments of the posterior pituitary of a rat was not influenced by perfusion with Eagle MEM medium containing 10(-6) or 10(-5) M PGE2 and D2.

Assay of 2‐Hydroxyputrescine in Various Regions of Rat Brain by Gas Chromatography‐Mass Spectrometry

2‐Hydroxyputrescine in seven regions of single rat brains was measured with a sensitive, specific assay by gas chromatography‐mass spectrometry. The regions were the cerebral cortex, cerebellum, medulla oblongata, hypothalamus, striatum, hippocampus, and midbrain. The level of 2‐hydroxyputrescine was very high in the cerebral cortex and cerebellum, high in the medulla oblongata, hypothalamus, and hippocampus, and low in the striatum and mid‐brain. The level of 2‐hydroxyputrescine in the cerebellum was significantly higher than in the striatum and midbrain.

Formation of GABOB from 2-hydroxyputrescine and its anticonvulsant effect

To investigate the formation of gamma-amino-beta-hydroxybutyric acid from 2-hydroxyputrescine in mammalian organs, the radioactive diamine was synthesized and was injected into rats intraperitoneally or intraventricularly. After intraperitoneal injection, the radioactive amino acid was detected in various organs, but formation of the stereoisomer of the amino acid (gamma-amino-alpha-hydroxybutyric acid) was not demonstrated. Intraventricular injection of the radioactive diamine also resulted in the formation of gamma-amino-beta-hydroxybutyric acid in the rat brain. In vivo experiments using monoamine oxidase or diamine oxidase inhibitors suggested the participation of both enzymes in the formation of the amino acid from the diamine in rat organs other than the brain, where diamine oxidase appeared to play the major role. To investigate the anticonvulsant effect of 2-hydroxyputrescine, the threshold of pentylenetetrazol-induced generalized convulsions was measured in rats after the intraventricular injection of 2-hydroxyputrescine. Both R(-)- and S(+)-2-hydroxyputrescine had an anticonvulsant effect, with a greater elevation of the threshold being observed after injection of the R(-) form. Time course experiments suggested that this anticonvulsant effect depended on the formation of gamma-amino-beta-hydroxybutyric acid from 2-hydroxyputrescine in the rat brain. The anticonvulsant action of gamma-amino-beta-hydroxybutyric acid was also examined, and the stimulation of Cl- influx plus the inhibition of GABA uptake into brain membrane vesicles were indicated to be involved.