Effects of excitotoxic amino acids on pituitary hormone secretion in the rat

The acute effects of administration of 4 excitatory amino acids (n-methyl-DL-aspartic acid (NMA), kainic acid (KA), ibotenic acid (IA) and quinolinic acid (QA] on the serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), growth hormone (GH) and prolactin (PRL) were studied in the rat. NMA-treated rats exhibited increased serum LH and GH concentrations while KA-treated rats-showed increases only in serum GH concentrations. Neither IA nor QA altered adenohypophyseal hormone levels. These endocrine alterations induced by NMA and KA are different from those previously reported after administration of glutamate, another excitatory amino acid. The finding that all of the excitatory amino acids studied did not produce identical effects on anterior pituitary hormone secretion may be due to differential permeability of these substances into the central nervous system or because they act at different subtypes of excitatory amino acid receptors.