Glutamate inhibition of the adrenergic-stimulated production of melatonin in rat pineal gland in vitro.
The effect of L-glutamate on the adrenergic-stimulated release of melatonin in the rat pineal gland was examined using an in vitro perfusion system. L-Glutamate by itself had no effect on melatonin secretion whereas L-glutamate administered prior to (-)-isoproterenol (beta-adrenergic agonist) and L-phenylephrine (alpha-adrenergic agonist) inhibited melatonin production by 42%. L-Glutamate did not inhibit melatonin secretion when glands were stimulated with (-)-isoproterenol alone. D-Glutamate, as well as the L-glutamate agonists kainate, N-methyl-D-aspartate, quisqualate, and trans-1-aminocyclopentane-1,3-dicarboxylic acid, had no effect on the (-)-isoproterenol- and L-phenylephrine-stimulated secretion of melatonin, which suggests that the inhibitory effects of glutamate are not mediated via any of the known glutamate receptor subtypes. The possibility that L-glutamate may be converted to another neuroactive compound (GABA) prior to the addition of (-)-isoproterenol and L-phenylephrine is suggested by the observation that simultaneous administration of L-glutamate with (-)-isoproterenol and L-phenylephrine did not inhibit melatonin production.
Kus
L
L
Department of Cell Biology, Neurobiology, and Anatomy, Loyola University Chicago, Maywood, Illinois.
Handa
R J
RJ
McNulty
J A
JA
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D008297:Male; D008550:Melatonin / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D010870:Pineal Gland / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013566:Sympathomimetics / Q000494:pharmacology*
D000596:Amino Acids; D005971:Glutamates; D013566:Sympathomimetics; D018698:Glutamic Acid; D008550:Melatonin