Direct in vivo measurement of glycine and the neurochemical profile in the rat medulla oblongata.
The medulla oblongata (MO) contains a high density of glycinergic synapses and a particularly high concentration of glycine. The aims of this study were to measure directly in vivo the neurochemical profile, including glycine, in MO using a spin-echo-based (1)H MRS sequence at TE = 2.8 ms and to compare it with three other brain regions (cortex, striatum and hippocampus) in the rat. Glycine was quantified in MO at TE = 2.8 ms with a Cramér-Rao lower bound (CRLB) of approximately 5%. As a result of the relatively low level of glycine in the other three regions, the measurement of glycine was performed at TE = 20 ms, which provides a favorable J-modulation of overlapping myo-inositol resonance. The other 14 metabolites composing the neurochemical profile were quantified in vivo in MO with CRLBs below 25%. Absolute concentrations of metabolites in MO, such as glutamate, glutamine, γ-aminobutyrate, taurine and glycine, were in the range of previous in vitro quantifications in tissue extracts. Compared with the other regions, MO had a three-fold higher glycine concentration, and was characterised by reduced (p < 0.001) concentrations of glutamate (-50 ± 4%), glutamine (-54 ± 3%) and taurine (-78 ± 3%). This study suggests that the functional specialisation of distinct brain regions is reflected in the neurochemical profile.
Xin
Lijing
L
Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland. lijing.xin@epfl.ch
Gambarota
Giulio
G
Duarte
João M N
JM
Mlynárik
Vladimír
V
Gruetter
Rolf
R
D000818:Animals; D002540:Cerebral Cortex / Q000737:chemistry / Q000378:metabolism; D003342:Corpus Striatum / Q000737:chemistry / Q000378:metabolism; D005998:Glycine / Q000378:metabolism*; D006624:Hippocampus / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008526:Medulla Oblongata / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D005998:Glycine