Abstract
Influences of amino acids and monoamines on the single unit discharges of the suprachiasmatic nucleus (SCN) were investigated using hypothalamic slice preparations. lontophoretic application of GABA inhibited 90% and taurine inhibited 40% of SCN neurons, while glycine inhibited only 4%. L-glutamate excited about 50% of the neurons. Serotonin, noradrenaline and dopamine inhibited 30, 22 and 26% of the SCN neurons, respectively. Amino acid effects were observed equally in both the ventrolateral part of the SCN and the remaining part of it, while monoamine effects were observed preferentially in the ventrolateral part of the SCN where the optic fibers and serotonin nerves terminated. These results suggest that amino acids and monoamines modulate the neuronal activity of the SCN through their direct effects.
