Premium
Calcium‐Dependent Effects of Melatonin Inhibition of Glutamatergic Response in Rat Striatum
Author(s) -
Escames G.,
Macías M.,
León J.,
García J.,
Khaldy H.,
Martín M.,
Vives F.,
AcuñaCastroviejo D.
Publication year - 2001
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1046/j.1365-2826.2001.00656.x
Subject(s) - melatonin , medicine , endocrinology , excitatory postsynaptic potential , chemistry , striatum , diltiazem , glutamatergic , glutamate receptor , inhibitory postsynaptic potential , calcium , biology , receptor , dopamine
The effects of melatonin, amlodipine, diltiazem ( l ‐type Ca 2+ channel blockers) and ω‐conotoxin ( N ‐type Ca 2+ channel blocker) on the glutamate‐dependent excitatory response of striatal neurones to sensory‐motor cortex stimulation was studied in a total of 111 neurones. Iontophoresis of melatonin produced a significant attenuation of the excitatory response in 85.2% of the neurones with a latency period of 2 min. Iontophoresis of either l ‐ or N ‐type Ca 2+ channel blocker also produced a significant attenuation of the excitatory response in more than 50% of the recorded neurones without significant latency. The simultaneous iontophoresis of melatonin + amlodipine or melatonin + diltiazem did not increase the attenuation produced by melatonin alone. However, the attenuation of the excitatory response was significantly higher after ejecting melatonin + ω‐conotoxin than after ejecting melatonin alone. The melatonin–Ca 2+ relationship was further supported by iontophoresis of the Ca 2+ ionophore A‐23187, which suppressed the inhibitory effect of either melatonin or Ca 2+ antagonists. In addition, in synaptosomes prepared from rat striatum, melatonin produced a decrease in the Ca 2+ influx measured by Fura‐2AM fluorescence. Binding experiments with [ 3 H]MK‐801 in membrane preparations from rat striatum showed that melatonin did not compete with the MK‐801 binding sites themselves although, in the presence of Mg 2+ , melatonin increased the affinity of MK‐801. The results suggest that decreased Ca 2+ influx is involved in the inhibitory effects of melatonin on the glutamatergic activity of rat striatum.