Effect of excitatory amino acids on rat hypothalamic somatostatin secretion in vitro.
We studied the effect of various agonists of excitatory amino acid (EAA) receptor subtypes on somatostatin (SRIF) release from incubated rat hypothalamic slices. N-Methyl-D-aspartic acid (NMDA) and L-glutamate (1 x 10(-7) to 1 x 10(-3) M) stimulated, in a dose-dependent fashion, SRIF release. The maximal effect was obtained at a concentration of 1 x 10(-4) M for both drugs. The IC50 was 3.2 x 10(-5) M and 2.1 x 10(-5) M for NMDA and L-glutamate, respectively. Incubation with 2.5 x 10(-4) M D-2-amino-5-phosphonovalerate (a NMDA receptor antagonist) or 2-amino-4-phosphonobutyrate (a metabotropic receptor antagonist) was without significant effect on basal SRIF secretion and completely blocked the increase in SRIF release induced by 5 x 10(-5) M NMDA or L-glutamate, respectively. Incubation with 1 x 10(-4) M kainate or 0.5 x 10(-4) M alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) did not change basal SRIF secretion. Incubation with 2 x 10(-4) M gamma-D-glutamylglycine (a specific antagonist of kainate and AMPA receptors) had no effect under basal conditions or during exposure to kainate or AMPA. Our data demonstrate that EAAs stimulate SRIF secretion in vitro, by an action through NMDA and metabotropic receptors but not kainate or AMPA receptors.
Joanny
P
P
Laboratoire de Neuroendocrinologie Expérimentale, INSERM U 297, Marseille, France.
Steinberg
J
J
Oliver
C
C
Grino
M
M
D000818:Animals; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018846:Excitatory Amino Acids / Q000494:pharmacology*; D018698:Glutamic Acid / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects* / Q000378:metabolism*; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000494:pharmacology; D008297:Male; D016202:N-Methylaspartate / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017470:Receptors, Glutamate / Q000145:classification / Q000187:drug effects; D013004:Somatostatin / Q000378:metabolism*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D018846:Excitatory Amino Acids; D017470:Receptors, Glutamate; D018698:Glutamic Acid; D013004:Somatostatin; D016202:N-Methylaspartate; D011189:Potassium Chloride; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D007608:Kainic Acid