Efficacy of Tryptophan for the Treatment of Nonketotic Hyperglycinemia: A New Therapeutic Approach for Modulating the N-Methyl-D-aspartate Receptor

PEDIATRICS ◽  
1995 ◽  
Vol 95 (1) ◽  
pp. 142-146
Author(s):  
Satoshi Matsuo ◽  
Fumio Inoue ◽  
Yoshihiro Takeuchi ◽  
Hiroshi Yoshioka ◽  
Akihiko Kinugasa ◽  
...  
Keyword(s):  
Excitatory Amino Acid ◽  
Muscular Hypotonia ◽  
Inherited Disease ◽  
Excitatory Amino Acid Receptors ◽  
Amino Acid Receptors ◽  
Aspartate Receptor ◽  
Cleavage Enzyme ◽  
Glycine Cleavage ◽  
Glycine Level ◽  
Nonketotic Hyperglycinemia

Nonketotic hyperglycinemia (NKH) is a rare inherited disease caused by a defect of the glycine cleavage enzyme.1 Especially in the neonatal type, neurological symptoms such as muscular hypotonia, seizures, respiratory distress, and lethargy develop rapidly, and the prognosis is unfavorable.1 Elevation of glycine in the cerebrospinal fluid (CSF) is thought to be responsible for these symptoms. However, management is quite difficult, because it is not well understood how elevation of glycine causes these symptoms. Lowering of the glycine level in CSF with sodium benzoate is not enough to avoid severe psychomotor and mental retardation. The N-methyl-D-aspartate (NMDA) receptor, which is one of the excitatory amino acid receptors, has a glycine binding site.2

Excitatory amino acid receptors in commissural nucleus of the NTS mediate carotid chemoreceptor responses

1993 ◽  
Vol 264 (1) ◽  
pp. R41-R50 ◽  
Author(s):  
A. Vardhan ◽  
A. Kachroo ◽  
H. N. Sapru
Keyword(s):  
Amino Acid ◽  
Carotid Body ◽  
Excitatory Amino Acid ◽  
Minute Ventilation ◽  
Neuronal Cell ◽  
Excitatory Amino Acid Receptors ◽  
Amino Acid Receptors ◽  
Neuronal Cell Bodies ◽  
Carotid Body Chemoreceptors ◽  
Stimulation Of

Stimulation of carotid body chemoreceptors by saline saturated with 100% CO2 elicited an increase in mean arterial pressure, respiratory rate, tidal volume, and minute ventilation (VE). Microinjections of L-glutamate into a midline area 0.5-0.75 mm caudal and 0.3-0.5 mm deep with respect to the calamus scriptorius increased VE. Histological examination showed that the site was located in the commissural nucleus of the nucleus tractus solitarii (NTS). The presence of excitatory amino acid receptors [N-methyl-D-aspartic acid (NMDA); kainate, quisqualate/alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) and trans 1-amino-cyclopentane-trans-1,3-dicarboxylic acid (ACPD)] in this area was demonstrated by microinjections of appropriate agonists. Simultaneous blockade of NMDA and non-NMDA receptors by combined injections of DL-2-aminophosphonoheptanoate (AP-7; 1 nmol) and 6,7-dinitro-quinoxaline-2,3-dione (DNQX; 1 nmol) abolished the responses to stimulation of carotid body on either side. Combined injections of AP-7 and DNQX did not produce a nonspecific depression of neurons because the responses to another agonist, carbachol, remained unaltered. Inhibition of the neurons in the aforementioned area with microinjections of muscimol (which hyperpolarizes neuronal cell bodies but not fibers of passage) also abolished the responses to subsequent carotid body stimulation on either side.(ABSTRACT TRUNCATED AT 250 WORDS)

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