H. Saito

Bio: H. Saito is an academic researcher from Iwate Medical University. The author has contributed to research in topics: Acetylcholine & Monoamine neurotransmitter. The author has an hindex of 9, co-authored 21 publications receiving 210 citations.

Rapid and simultaneous assay of monoamine neurotransmitters and their metabolites in discrete brain areas of mice by HPLC with Coulometric detection

Abstract: For simultaneous assay of the three monoamine neurotransmitters, norepinephrine, dopamine, and serotonin, and four respective metabolites in brain tissue, a rapid and simple method using high-performance liquid chromotography with coulometric detection is described. Because the present method permits the determination of these target substrates within 10 min or less in one chromotographic run, 150 samples can be analyzed using an autosampler and an integrator in a 24-h period. Within-run coefficients of variation for the target substrates in the standard solution and the whole brain sample were less than 3% and 2% (n = 40), respectively. The quantitative detection limits were 0.01-0.1 pmol. The present procedure was applied to measure the target substrates in several discrete brain areas in mice.

A rapid assay for neurotransmitter amino acids, aspartate, glutamate, glycine, taurine and γ-aminobutyric acid in the brain by high-performance liquid chromatography with electrochemical detection

Abstract: For simultaneous assay of the five neurotransmitter amino acids, Asp, Glu, Gly, Tau, and GABA in brain tissues, a very rapid and simple chromatographic method using high-performance liquid chromatography with electrochemical detection in combination with o-phthalaldehyde derivatization is described. Because the present method permits the determination of these five amino acids within less than five minutes in one chromatographic run, up to 100 samples a working day can be analyzed using an autosampler. Withinrun coefficients of variation for these five amino acids were less than 2% (n=20). The quantitative detection limit was 2.5 pmol for the 5 amino acids. The present method has been applied to the measurement of the five amino acid neurotransmitter levels in several discrete brain regions of mice treated with and without electroconvulsive shock.

MKC-231, a choline uptake enhancer, ameliorates working memory deficits and decreased hippocampal acetylcholine induced by ethylcholine aziridinium ion in mice

Abstract: The effects of acute and chronic administration of MKC-231, a new choline uptake enhancer, and two other nootropic agents, linopiridine (Dup 996) and tetrahydroaminoacridine (THA) on working memory deficits and decreased hippocampal acetylcholine (ACh) content were studied in a delayed non-matching to sample task, using a T-maze, in ethylcholine aziridinium ion (AF64A)-treated mice. Treatment with AF64A (3.5 nmol, i.c.v.) produced memory deficits and decreased hippocampal ACh content. In acute behavioral experiments, MKC-231 and THA had no significant effect on AF64A-induced memory deficits at any doses tested (0.3, 1.0 and 3.0 mg/kg), whereas Dup 996, at a dose of 1.0 mg/kg, significantly improved memory deficits. In chronic experiments, MKC-231 improved memory deficit at all doses tested (0.3, 1.0, or 3.0 mg/kg p.o., once daily for 11 days) and Dup 996 did so only at a dose of 3.0 mg/kg, whereas THA did not improve memory deficit at any doses tested. In acute neurochemical experiments, MKC-231 and THA did not reverse the AF64A-induced hippocampal ACh depletion. Dup 996, however, further decreased hippocampal ACh content compared to that in the AF64A-treated group. In chronic experiments, MKC-231 significantly reversed hippocampal ACh depletion at doses of 0.3 and 1.0 mg/kg, whereas neither Dup 996 nor THA reversed hippocampal ACh depletion at any doses tested. These results indicate that MKC-231 improved the AF64A-induced working memory deficit and hippocampal ACh depletion, probably by recovering reduced high-affinity choline uptake and ACh release.

Regulatory Effect of Danggui-Shaoyao-San on Central Cholinergic Nervous System Dysfunction in Mice

Abstract: Since administration of a powdered extract (TSS) of Danggui-Shaoyao-San (Toki-shakuyaku-san in Japanese) alone to naive mice had no influence on ACh levels in the brain, the present study examined the effect of TSS on the central cholinergic nervous system using mice treated with scopolamine (0.5 mg/kg) or mecamylamine (0.05 mg/kg), which affects the cholinergic nervous system. TSS was suspended in a 5% carboxymethylcellulose solution and mice were orally given single or repeated (twice a day, for 14 days) administration of TSS at 50 or 500 mg/kg. Results on spontaneous locomotor activity showed that (1) single administration of TSS at 50 or 500 mg/kg to naive mice significantly inhibited vertical and horizontal locomotor activities, while repeated administration of TSS at 50 mg/kg significantly stimulated both activities; (2) in mice treated with scopolamine, repeated administration of TSS at 500 mg/kg significantly inhibited the scopolamine-induced increase in locomotor activities, whereas in mice treated with mecamylamine, single or repeated administration of TSS at 50 and 500 mg/kg did not show any influence on the mecamylamine-induced decrease in locomotor activities. Regarding the step-down passive avoidance responses; single administration, but not repeated administration, of TSS at 50 and 500 mg/kg significantly inhibited scopolamine-induced shortening of step-down latency. In mice treated with mecamylamine, TSS did not exert any influence on the step-down latency. As for ACh contents, single or repeated administration of TSS at 50 or 500 mg/kg to naive mice had no influence on the levels of ACh in the cerebral cortex, corpus striatum or hippocampus. However, the levels of brain ACh in mice treated with scopolamine showed a decrease and a single administration of TSS at 500 mg/kg significantly inhibited this scopolamine-induced decrease in ACh levels. These results indicate that TSS ameliorates dysfunction of the central cholinergic nervous system and scopolamine-induced decrease in ACh levels in mouse brain, but has no influence on ACh levels in naive mice. Thus, it suggests that TSS may be a useful therapeutic agent in Alzheimer's disease and senile dementia.

The neuropsychology of 3-D space

Abstract: The neuropsychological literature on 3-D spatial interactions is integrated using a model of 4 major behavioral realms: (a) peripersonal (visuomotor operations in near-body space), (b) focal extrapersonal (visual search and object recognition), (c) action extrapersonal (orienting in topographically defined space), and (d) ambient extrapersonal (orienting in earth-fixed space). Each is associated with a distinct cortical network: dorsolateral peripersonal, predominantly ventrolateral focal-extrapersonal, predominantly ventromedial action-extrapersonal, and predominantly dorsomedial ambient-extrapersonal systems. Interactions in 3-D space are also regulated neurochemically with dopaminergic and cholinergic excitation associated with extrapersonal activation and noradrenergic and serotonergic excitation associated with peripersonal activation. This model can help explain the 3-D imbalances in prominant neuropsychological disorders.

M3 muscarinic acetylcholine receptor plays a critical role in parasympathetic control of salivation in mice

Abstract: The M1 and M3 subtypes are the major muscarinic acetylcholine receptors in the salivary gland and M3 is reported to be more abundant. However, despite initial reports of salivation abnormalities in M3-knockout (M3KO) mice, it is still unclear which subtype is functionally relevant in physiological salivation. In the present study, salivary secretory function was examined using mice lacking specific subtype(s) of muscarinic receptor. The carbachol-induced [Ca2+]i increase was markedly impaired in submandibular gland cells from M3KO mice and completely absent in those from M1/M3KO mice. This demonstrates that M3 and M1 play major and minor roles, respectively, in the cholinergically induced [Ca2+]i increase. Two-dimensional Ca2+-imaging analysis revealed the patchy distribution of M1 in submandibular gland acini, in contrast to the ubiquitous distribution of M3. In vivo administration of a high dose of pilocarpine (10 mg kg−1, s.c.) to M3KO mice caused salivation comparable to that in wild-type mice, while no salivation was induced in M1/M3KO mice, indicating that salivation in M3KO mice is caused by an M1-mediated [Ca2+]i increase. In contrast, a lower dose of pilocarpine (1 mg kg−1, s.c.) failed to induce salivation in M3KO mice, but induced abundant salivation in wild-type mice, indicating that M3-mediated salivation has a lower threshold than M1-mediated salivation. In addition, M3KO mice, but not M1KO mice, had difficulty in eating dry food, as shown by frequent drinking during feeding, suggesting that salivation during eating is mediated by M3 and that M1 plays no practical role in it. These results show that the M3 subtype is essential for parasympathetic control of salivation and a reasonable target for the drug treatment and gene therapy of xerostomia, including Sjogren's syndrome.

Quantitative proton-decoupled 31P MRS and 1H MRS in the evaluation of Huntington's and Parkinson's diseases

Abstract: Objective: To determine cerebral energy status in patients with Huntington9s disease(HD) and Parkinson9s disease (PD). Methods: The study included 15 patients with DNA-proven, symptomatic HD and five patients with medically treated, idiopathic PD, all of whom were candidates for neurotransplant treatment, as well as 20 age-related normal subjects. Quantitative noninvasive, MRI-guided proton MRS was performed of single volumes in putamen of basal ganglia (BG), occipital gray matter, and posterior parietal white matter; in addition, quantitative phosphorus and proton-decoupled phosphorus MRS of superior biparietal white and gray matter was done. Outcome measures were quantitative metabolite ratios and millimolar concentrations of neuronal and glial markers, creatine (Cr) and adenosine triphosphate (ATP), and intracellular pH. Results: In volume-corrected control BG (10.46 ± 0.37 mM), [Cr] was 29%( p Conclusion: Previously described failure of global energy metabolism in HD was not confirmed. However, quantitative 1-hydrogen MRS and decoupled 31-phosphorus MRS are sensitive to ±10% alterations in key cerebral metabolites, and may be of value in noninvasive monitoring of appropriate therapies.

The choline transporter resurfaces: new roles for synaptic vesicles?

Abstract: Presynaptic choline uptake is vital to sustained neuronal acetylcholine (ACh) release; however, only with the recent cloning of choline transporters (CHTs) (i.e., SLC5A7), has a picture emerged of the regulatory pathways supporting CHT modulation. Studies arising from the development of CHT-specific antibodies reveal a large, intracellular reserve of CHT proteins, localized to ACh-containing, synaptic vesicles. The intersection of mechanisms supporting vesicular ACh release and choline uptake demonstrates an elegant mechanism for linking regulation of CHT membrane density to rates of ACh release. Furthermore, these studies point to control of the CHT endocytic process as an important target for novel therapeutics that could offset functional deficits in disorders bearing diminished cholinergic tone, including myasthenias and dementias.

Interaction between transcellular and paracellular water transport pathways through Aquaporin 5 and the tight junction complex

Abstract: To investigate potential physiological interactions between the transcellular and paracellular pathways of water transport, we asked whether targeted deletion of Aquaporin 5 (AQP5), the major transcellular water transporter in salivary acinar cells, affected paracellular transport of 4-kDa FITC-labeled dextran (FITC-D), which is transported through the paracellular but not the transcellular route. After i.v. injection of FITC-D into either AQP5 wild-type or AQP5−/− mice and saliva collection for fixed time intervals, we show that the relative amount of FITC-D transported in the saliva of AQP5−/− mice is half that in matched AQP5+/+ mice, indicating a 2-fold decrease in permeability of the paracellular barrier in mice lacking AQP5. We also found a significant difference in the proportion of transcellular vs. paracellular transport between male and female mice. Freeze-fracture electron microscopy revealed an increase in the number of tight junction strands of both AQP5+/+ and AQP5−/− male mice after pilocarpine stimulation but no change in strand number in female mice. Average acinar cell volume was increased by ≈1.4-fold in glands from AQP5−/− mice, suggesting an alteration in the volume-sensing machinery of the cell. Western blots revealed that expression of Claudin-7, Claudin-3, and Occludin, critical proteins that regulate the permeability of the tight junction barrier, were significantly decreased in AQP5−/− compared with AQP5+/+ salivary glands. These findings reveal the existence of a gender-influenced molecular mechanism involving AQP5 that allows transcellular and paracellular routes of water transport to act in conjunction.