DIFFERENTIAL ONTOGENIC PATTERN OF METABOTROPIC [H-3] L-GLUTAMATE RECEPTORS IN NORMAL AND GRANULE CELL-DEFICIENT MOUSE CEREBELLUM

[H-3]-L-glutamate binding site distribution corresponding to metabotro pic receptors was studied by autoradiography during normal and altered cerebellar ontogeny in mice treated on postnatal days (PND) 5 and 6 w ith the antimitotic methylazoxymethanol (MAM). Quisqualate (QA)-induce d and (2S, 3S, 4S)-alpha-(carboxycyclopropyl)-glycine (L-CCG-I)-induce d [H-3]-L-glutamate binding inhibition allowed us to distinguish betwe en group I and group II metabotropic receptor binding sites. In contro l cerebellar cortex, the QA-sensitive binding site density increases d uring development, while the L-CCG-I-sensitive binding site density de creases. In the deep cerebellar nuclei (DCN), both populations of bind ing sites decrease during ontogeny. The antimitotic treatment induces: (1) a slight but significant increase in the QA-sensitive binding sit es in the DCN at PND 10 and in the cerebellar cortex beginning from PN D 20; (2) a retarded decrease in the L-CCG-I-sensitive metabotropic re ceptor binding site density. These differences could be due to a retar ded cell maturation and/or an over-expression of some postsynaptic rec eptors in the adult cerebellum in response to the afference deficiency .