NMDA AND NON-NMDA SENSITIVE [L-H-3]GLUTAMATE RECEPTOR-BINDING IN THE BRAIN OF THE NAPLES HIGH-EXCITABILITY AND LOW-EXCITABILITY RATS - AN AUTORADIOGRAPHIC STUDY

The Naples high-excitability (NHE) and low-excitability (NLE) rat line s, selectively bred for high and low activity in a LBt maze, respectiv ely, are used as an animal model in the study of hippocampal functions . The aim of this study was to investigate the anatomical distribution of N-methyl-D-aspartate (NMDA) and non-NMDA sensitive [H-3]glutamate receptor binding by quantitative autoradiography in the brain of the N HE and NLE rats with a randomly bred line (NRB) as controls. Twenty-mi cron-thick cryostat sagittal sections were incubated at 4 degrees C wi th 150 nM [L-H-3]glutamate alone or in the presence of 100 mu M NMDA o r 2.5 mu M quisqualate (QA). Non-specific binding was determined in th e presence of 1 mM of non-labeled glutamate. The sections were exposed to tritium-sensitive films for 3 weeks at 4 degrees C. Quantitative a nalysis revealed: (1) higher levels of total binding in NHE than in NR B and NLE rats in all areas but the cerebellum; (2) fewer binding site s for both NMDA and QA receptors and larger binding sites for QA recep tors in the hippocampus of NLE and NHE rats, respectively; (3) a posit ive correlation between total binding sites and activity level in a LB t maze in all areas, except the cerebellar molecular layer with NLE<NH E, which was due to a differential contribution from NMDA and non-NMDA types. Thus, the brain of the NHE rats shows an imbalance between NMD A and non-NMDA sensitive [L-H-3]glutamate receptors.