TY - JOUR
T1 - Melatonin disrupts circadian rhythms of glutamate and GABA in the neostriatum of the awake rat
T2 - A microdialysis study
AU - De Marquez Prado, B.
AU - Castañeda, T. R.
AU - Galindo, A.
AU - Del Arco, A.
AU - Segovia, G.
AU - Reiter, R. J.
AU - Mora, F.
PY - 2000
Y1 - 2000
N2 - The purpose of this study was to investigate possible circadian changes in extracellular concentrations of glutamate (GLU) and γ-aminobutyric acid (GABA), and the influence of melatonin on the levels of these neurotransmitters in the neostriatum of awake rats using in vivo microdialysis. At the same time, the concentrations of the amino acids taurine (TAU), glutamine (GLN) and arginine (ARG), as well as dopamine (DA) and its metabolites 3, 4-dihydroxyphenyl acetic acid (DOPAC) and homovanillic acid (HVA), were measured in the extracellular fluid. When dialysates were collected over a 24-hr period (6 hr dark, 12 hr light, 6 hr dark), both GLU and GABA, without the infusion of melatonin, exhibited statistically significant rhythms, with higher levels of these constituents during the dark and lower levels during the day. Perfusion with melatonin (for 19 consecutive hours) prevented the daytime reductions in both GLU and GABA. Of the amino acids measured in the dialysates collected from the neostriatum of non-perfused rats, only ARG exhibited a significant change during the light:dark cycle; again, lowest concentrations were measured during the day. While melatonin perfusion did not statistically significantly influence neostriatal levels of TAU and ARG, GLN levels continued to drop during the infusion of the indoleamine. Dialysate concentrations of DA, DOPAC and HVA exhibited circadian rhythms which were not influenced by melatonin perfusion. The findings indicate there are differential effects of melatonin on extracellular neurotransmitter concentrations in the neostriatum of the awake rat. The results also suggest that the day:night variations in GLU and GABA may relate to daily changes in endogenous melatonin production, while DA and its metabolites are minimally influenced by this secretory product.
AB - The purpose of this study was to investigate possible circadian changes in extracellular concentrations of glutamate (GLU) and γ-aminobutyric acid (GABA), and the influence of melatonin on the levels of these neurotransmitters in the neostriatum of awake rats using in vivo microdialysis. At the same time, the concentrations of the amino acids taurine (TAU), glutamine (GLN) and arginine (ARG), as well as dopamine (DA) and its metabolites 3, 4-dihydroxyphenyl acetic acid (DOPAC) and homovanillic acid (HVA), were measured in the extracellular fluid. When dialysates were collected over a 24-hr period (6 hr dark, 12 hr light, 6 hr dark), both GLU and GABA, without the infusion of melatonin, exhibited statistically significant rhythms, with higher levels of these constituents during the dark and lower levels during the day. Perfusion with melatonin (for 19 consecutive hours) prevented the daytime reductions in both GLU and GABA. Of the amino acids measured in the dialysates collected from the neostriatum of non-perfused rats, only ARG exhibited a significant change during the light:dark cycle; again, lowest concentrations were measured during the day. While melatonin perfusion did not statistically significantly influence neostriatal levels of TAU and ARG, GLN levels continued to drop during the infusion of the indoleamine. Dialysate concentrations of DA, DOPAC and HVA exhibited circadian rhythms which were not influenced by melatonin perfusion. The findings indicate there are differential effects of melatonin on extracellular neurotransmitter concentrations in the neostriatum of the awake rat. The results also suggest that the day:night variations in GLU and GABA may relate to daily changes in endogenous melatonin production, while DA and its metabolites are minimally influenced by this secretory product.
KW - Amino acid neurotransmitters
KW - Dopamine and metabolites
KW - Glutamate
KW - Melatonin
KW - Neostriatum
KW - γ-Aminobutyric acid
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U2 - 10.1034/j.1600-0633.2002.290403.x
DO - 10.1034/j.1600-0633.2002.290403.x
M3 - Article
C2 - 11068943
AN - SCOPUS:0033786882
SN - 0742-3098
VL - 29
SP - 209
EP - 216
JO - Journal of Pineal Research
JF - Journal of Pineal Research
IS - 4
ER -