Release of 3H-Noradrenaline by Excitatory Amino Acids From Rat Mediobasal Hypothalamus and the Influence of Aging

CARLOS E. NAVARRO; RICARDO J. CABRERA; ALFRED0 0. DONOSO

BRAIN RESEARCH BULLETIN

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 1994 vol. 33 p. 677 - 682

0361-9230

NAVARRO, C. E., R. J. CABRERA AND A. 0. DONOSO. Release of 3H-noradrenaline by excitatory amino acids from ratmediobasal hypothalamus and the influence of aging. BRAIN RES BULL 33(6) 677-682,1994.-The present study was designedto analyze the effects of glutamate (GLU) and its agonists on the release of noradrenaline (NA) from the mediobasal region of rathypothalamus (MBH). Slices from hypothalamus were loaded in vitro with 3H-NA and thereafter exposed to GLU and the glutamateagonists N-methyl-D-aspartic acid (NMDA) and kainate (RA), in superfusion chambers. GLU evoked a significant 3H-NA releasein a concentration-dependent manner. The E& was 35 mM. 6-Cyano-7-nitro-quinoxaline-2,3-dione (CNQX), a non-NMDAselective antagonist, and amino-7-phosphonoheptanoic acid (AI’ 7), a NMDA selective antagonist, both decreased the GLU-evokedresponse to about 50% of its value. NMDA, superfused in Mg *+-free Krebs-Ringer, exhibited a greater potency than GLU withan EC,, = 124 PM. KA was also able to evoke 3H-NA release, although overall responses to KA were lower than those of NMDA.The maximal response to KA was a 36% increase of release at a concentration of 200 MM. The effect of KA was blunted byCNQX. NMDA-induced ‘H-NA release was progressively altered with age. In old rats (16-18 months) and middle-aged rats (10months), responses to 200 PM NMDA were decreased respect to young (4 months) male rats. These results show that NMDAand KA receptors mediate the excitatory effects of GLU on NA release from nerve terminals in the MBH and suggest that GLU,in association with NA, participates in the complex mechanisms that regulate neuroendocrine functions. In addition, the age-relatedchanges in NA responsiveness point to a GLU contribution on the maintenance of the reproductive status.