Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5736264 | Brain Research Bulletin | 2017 | 30 Pages |
Abstract
Theanine is a non-dietary amino acid linked to the modulation of synaptic transmission in the central nervous system, although the acute effects of theanine in vivo, particularly on nociceptive transmission in the trigeminal system, remain to be determined. The present study investigated whether acute intravenous theanine administration to rats attenuates the excitability of wide dynamic range (WDR) spinal trigeminal nucleus caudalis (SpVc) neurons in response to nociceptive and non-nociceptive mechanical stimulation in vivo. Extracellular single unit recordings were made from 15 SpVc neurons in response to orofacial mechanical stimulation of pentobarbital-anesthetized rats, and responses to non-noxious and noxious mechanical stimuli were analyzed. The mean firing frequency of SpVc WDR neurons in response to all mechanical stimuli was dose-dependently inhibited by theanine (10, 50, and 100Â mM, i.v.) with the maximum inhibition of discharge frequency reached within 5Â min. These inhibitory effects were reversed after approximately 10Â min. The relative magnitude of theanine's inhibition of SpVc WDR neuronal discharge frequency was significantly greater for noxious than non-noxious stimulation. Iontophoretic application of l-glutamate induced the mean firing frequency of SpVc WDR neuron responding to noxious mechanical stimulation was also inhibited by intravenous administration of 100Â mM theanine. These results suggest that acute intravenous theanine administration suppresses glutaminergic noxious synaptic transmission in the SpVc, implicating theanine as a potential complementary and alternative therapeutic agent for the treatment of trigeminal nociceptive pain.
Keywords
N-methyl-d-aspartatespinal trigeminal nucleus caudalisα-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acidtrigeminal spinal nucleus caudalisSpVcWDRNMDAAMPADRGSSSdorsal root ganglionγ-aminobutyric acidTheanineanalysis of varianceANOVACAMsuperior sagittal sinussingle unit recordingcomplementary and alternative medicinewide dynamic rangenociceptionGABA
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Authors
Shiori Takehana, Yoshiko Kubota, Nobuo Uotsu, Kei Yui, Yoshihito Shimazu, Mamoru Takeda,